Drug-testing methods and clinical interpretations of test results

Sections

ABSTRACT
Introduction
I. Drug properties: absorption, distribution and elimination phases
II. Selection of drugs to be tested
III. Types of testing. blood, urine and hair specimens
IV. Measuring impairment
V. Urine-testing methods
VI. Interpretation of test results
VII. Common adulteration methods
VIII. Laboratory procedural and security standards
IX. Initial and confirmatory testing requirements
X. Regulations for drug testing*

Details

Author: B. M. KAPUR
Pages: 115 to 154
Creation Date: 1993/01/01

Drug-testing methods and clinical interpretations of test results

B. M. KAPUR Director of Clinical Laboratory, Addiction Research Foundation, Toronto, Qntario, Canada

ABSTRACT

In the present paper, major issues related to drug testing are discussed. For example, drug-testing techniques measure the presence of a drug or drug but are not sophisticated enough to measure impairment from drug use. Moreover, it is difficult to determine the route of drug administration, quantity or frequency, as well as when the drug was taken, on the basis of the laboratory results.

Selection of the drug top be tested should depend on the local availability of the drug, its abuse potential and clinical effects, as well as on the availability of analytical technology and expertise in testing and in interpreting laboratory results. The most sophisticated drug-testing approach is gas chromatography coupled with mass spectrometry (GC/MS), which is regarded as a "gold standard"; it is used in confiramto0ry testing. Typically, GC/MS is preceded by a rapid immunoassay method to eliminate the majority of the "negative" samples.

Despite the existence of sophisticated drug-testing methods, it is still possible to obtaining incorrect test results and to detect adulterated urine samples.

A "positive" drug finding can have a serious impact on the livelihood of an individual, therefor, persons conducting such tests should adhere to the strictest standards of laboratory performance. Only qualified and experienced individuals with proper laboratory equipment should perform these analyses. The standards of laboratory performance ,must meet local legal and forensic requirements. Access to patient samples and laboratory records must be restricted in order to prevent the tampering of samples and results. In order to maintain confidentiality, the results must be communicated only to the medical review officer. Chain-of-custody documents and all file so that they can be examined in case of a legal challenge. The laboratory must have a complete record on quality control. Finally, specific initial and confirmatory testing requirements should be met.

Introduction

As interest increases in employment-related drug testing, the technologies and the interpretive skills of analysts continue to evolve. Although recent literature indicates that significant refinements and modifications have been made in drug-testing technology, the complexity of drug effects is so great that many problems exist in the interpretation of test results. The most frequent problems that confront the toxicology laboratory are associated with developing technology that can determine how much and when a drug was taken, how long after use the tests are capable of showing positive results, the causes and rates of false positives and false negatives, and how tests can be "beaten" by employees. In the present paper, these problems are discussed and the various laboratory procedures used to combat the problems are examined.

I. Drug properties: absorption, distribution and elimination phases

Detection of a drug depends largely on its absorption, distribution and elimination properties. There are various routes of drug administration; oral drinking, e.g. alcohol), intravenous (injecting into a vein, e.g. heroin) and inhalation (smoking, e.g. marijuana; snorting, e.g. cocaine; and sniffing, e.g. glue). Drugs taken orally are usually the slowest to be absorbed (i.e. by the brain and other body organs), whereas the intravenous and inhalation routes result in the fastest absorption. Once the drug enters the bloodstream it is rapidly distributed to the various tissues in the body. The amount of drug stored depends on the nature of the drug, the quantity, the duration of ingestion, the tissue holding the drug and the frequency of use.

Some drugs are fat-soluble and are deposited in fat tissues. For example, Δ-9-tetrahydrocannabinol (THC), the active ingredient in marijuana, is highly fat-soluble, resulting in a rapid reduction in levels of THC in the blood as the drug is distributed to the various tissues [ 1] . Some studies have shown that THC levels peak and start to decline in half the time it takes to smoke a marijuana "joint". Concentrations are known to fall by almost 90 per cent in the first hour [ 1] , [ 2] suggesting that a higher degree of sophistication in laboratory analysis is needed to detect fat-soluble drugs. Depending on the amount of drug stored, however, fat-soluble drugs. Depending on the amount of drug stored, however, detection in the urine may be possible for as long as 60 days after last use [ 3] . Ethanol or ethyl alcohol is the beverage alcohol that is consumed by people. Alcohol* is not fat-soluble and is distributed in the total body water [ 4] . Since blood is mostly made up of water, the presence of alcohol is more easily detectable than fat-soluble drugs like THC. The absorption and distribution phases are followed by an elimination phase. The liver is the major detoxification centre in the body; drugs are metabolized as blood circulates through the organ. The metabolites are then excreted into the urine through the kidneys. At the same time, drugs deposited in fat tissues are also slowly released into the bloodstream and metabolized.

Drugs vary by their elimination half -lives, which is the time required for the blood levels to decline by 50 per cent (see table 1). The half -life of a drug is heavily influenced by a variety of factors, including the individual's age, sex, physical condition and clinical status. A compromised liver and the concurrent presence of another disease or drug have the potential of enhancing the toxic effects of the drug by slowing down the elimination process. Under different clinical conditions, however, the process may be speeded up. Therefore, great variation may be found in the half -lives of the same drug.

Approximately six half -lives are required to eliminate 99 per cent of any drug. Because the half-life of cocaine is relatively short, averaging one hour [ 5] , only six hours are needed for the elimination of 99 per cent of the drug. Cocaine metabolites have a longer half -life and can be detected for a considerably longer period of time through urine drug assays. Compared with cocaine, phenobarbital has a much longer half - life (80-120 hours), so that at least 480 hours, or 20 days, are required to eliminate 99 per cent of the drug. Since there is much variation in the half -lives of different drugs and the absolute amount of drug present can be very small, it is crucial that the appropriate body fluid for analysis is selected for testing.

Elimination of ethanol follows a different pattern. Its levels decline almost linearly over time. The average elimination rate is between 15 mg/100 ml and 20 mg/100 ml (0.015-0.02 per cent) per hour, although rates of between 10 mg/100 ml and 30 mg/100 ml (0.01-0.03 per cent) per hour have also been observed. In the alcoholic patient, the elimination rate is generally higher. In forensic calculations, a rate of 15 mg/100 ml (0.015 per cent) per hour is usually used.

*The terms ethanol and alcohol are used interchangeably in the present paper.

Table 1.

Drug half-lives and approximate urine detection periods

Drug

Half-life a/

Detection period

Methamphetamine
12-34 hours
2-3 days
Amphetamine (metabolite of methamphetamine)
7-34 hours
 
Heroin
60-90 minutes
Minutes
Morphine (metabolite of heroin)
1.3-6.7 hours
 
Phencyclidine. (PCP)
7-16 hours
2-3 days
Cocaine
0.5-1.5 hours
A few hours
Benzoyltegonine (metabolite of cocaine)
5-7 hours
3-5 days
Δ-9-Tetrahydrocannabinol
14-38 hours
90 per cent fall in 1 hour (blood)
Δ-9-Tetrahydrocannabinolic acid (marijuana metabolite in urine)
 
Depending on use, anywhere between a few days and many weeks
Alcohol (ethanol)
Blood levels fall by an average of 15-18 mg/ 100 ml/hour
1.5-12 hours, depending on the peak blood level; urine is typically positive for an additional 1-2 hours
Source-R. C. Baselt, Disposition of Toxic Drugs and Chemicals in Man, 2nd ed. (Davis, California, Biomedical Publications, 1982)..
a/ The detection period is dose-dependent. The larger the dose, the longer the period that the drug or, metabolite can be detected in the urine.

II. Selection of drugs to be tested

A number of different criteria can be applied to the drug(s) or category of drugs that-should be tested or monitored. Drug availability, clinical effects and robustness of the analytical method(s) used for analysis are probably the most important.

A. Availability

Prescription patterns of psychoactive and other drugs vary from place to place and from Country to Country [ 6] , [ 7] . The abuse of the benzodiazepine nitrazepam is common in Europe but almost unknown in Canada and the United States of America, as it is not available on markets in North America. The psychoactive chemical cathine is the active ingredient in the leaves of the khat (Catha edulis) plant, which are chewed in north-eastern Africa; the practice does not appear to have crossed over to the European or the North American continent. In Canada, the narcotic drug codeine is available as over-the-counter, non- prescription medication, whereas tin the United States it is available only with a physician's prescription.

The wide availability of "legal" stimulants poses an interesting problem since they are commonly found in accident victims. A study carried out in the United States by. the National Transportation Safety Board [ 8] from October 1987 to September 1988 showed that over-the- counter stimulants - antihistamines.such as ephedrine, pseudoephdrine and phenylpropanolamine - were, commonly found in drivers killed in heavy truck accidents. Similar results have also been obtained based on data from emergency rooms gathered over a five -year period [ 9] as well as data from admissions in a trauma unit following motor vehicle accidents [ 10] , [ 11]

In the National Transportation Safety Board study [ 8] , almost all the amphetamine use was in California rather than in the other seven states in the study, suggesting that drug use varies not only from country to country, but also within a given country.

Thus, the selection of a drug to be tested and monitored that is appropriate for one country or place may not necessarily be appropriate for another.

B. Clinical effects

Drugs that manifest abuse potential. and impair behaviour to such an extent that job performance may -be affected are prime candidates for testing or monitoring in the workplace. Alcohol and cocaine are examples of such drugs.

C. Analytical methods

A false -positive finding can have a serious impact on the livelihood of the person being tested. Therefore-, special attention needs to be paid to the testing methods used. Ideally,, the analytical method should be specific for the drug being tested (i.e. no false positive) and should be easy and inexpensive to use. Confirmation methods should also be readily available. The availability of technical and scientific expertise to perform the tests is also essential.

The interpretation of the analytical results needs to be carefully considered as even a normal diet can sometimes result in a positive drug identification. Poppy seed ingestion [ 12] can result in a true-positive analytical report but it is a false positive for drug use. Some ethnic diets may also lead to such confounding problems; for example, food containing poppy seed is common during the Ramadan period in India.

What should be analysed? Ideally, the parent drug, rather than its metabolite should be looked for in the analysis, although this may not always be possible as some drugs are rapidly metabolized (e.g. heroin metabolism to morphine). The sensitivity of the analytical procedure should be dictated by the psychoactive pharmacological properties of the drugs. If the drug is shown to be devoid of abuse potential, then its detection beyond the time of pharmacological activity, although important in the clinical management of the patient, does not necessarily serve a useful purpose in a workplace drug-screening programme.

The guidelines developed by the National Institute on Drug Abuse (NIDA) [ 13] in the United States in April 1988 deal with five "illegal" drugs (marijuana, phencyclidine (PCP), amphetamine, cocaine and heroin). Rapid screening methods that allowed for 'mass screening' were available at that time, as were the confirmation methods for those five drugs. Mood-altering substances, such as benzodiazepines, barbiturates and stimulants, such as antihistamines, are at present excluded from the regulations in the United States. This is probably because of the much wider availability of those drugs as medication and the technological requirements for screening and monitoring them.

III. Types of testing. blood, urine and hair specimens

Blood and urine are the most commonly used fluids in the analysis for drugs. Blood, obtained by an invasive procedure, is available only in small quantities and drug concentration levels in blood are low. Urine is the preferred sample as it is available in larger volume, contains the metabolite and requires less invasive procedures in its collection. Both sampling procedures, however, have limitations as they only determine the absolute amount of drug present in the fluid being examined. That amount is dependent upon the amount of the drug used, when it was used last, and the half-life of the drug.

Recently, hair samples have been used to detect drug use [ 14] , [ 15] , [ 16] . There are a number of technical problems that must be overcome, however, before hair can be used as definitive proof of drug use. An advisory committee of the Society of Forensic Toxicology [ 17] has recently concluded that, 'because of these deficiencies, results of hair analysis alone do not constitute sufficient evidence of drug use for application in the workplace'.

Breath and various body fluids, such as sweat, saliva, blood and urine, have been used for alcohol analysis. Breath is commonly used by law enforcement authorities for such analysis. Although a number of variables [ 18] can affect the breath-blood ratio, the 2,100:1 alveolar breath-blood conversion ratio has been used and accepted for the Breathalyser [ 19] . Breath-testing equipment calibrated with a blood- breath conversion factor of 2,100 consistently underestimate actual blood alcohol concentrations [ 20] . The results of breath analysis may vary depending on the instruments used and on biological factors [ 21] , [ 22] . Potential errors in breath analysis can also be caused by the presence of residual alcohol in the mouth. Immediately after drinking, there is enough alcohol vapour in the mouth to give artificially high concentrations in breath analysis. Generally, this effect disappears after 20minutes but high values for as long as 45 minutes have been reported [ 23] .

All existing technologies are limited in terms of their capacity to determine how much of a drug was consumed or when it was consumed.

Blood and saliva concentrations reflect the current blood alcohol concentration, but generally a blood sample is used in hospitals for patients entering casualty wards. In programmes requiring monitoring of alcohol use, urine is probably the sample of choice [ 24] . Urine alcohol concentration, which represents the average blood alcohol concentration between voiding, has the potential of being "positive" while the blood may be "negative".

IV. Measuring impairment

Except in alcohol analysis, the degree to which a person is influenced or impaired by a drug at the time of the testing cannot be determined from test results alone. Correlations between positive blood levels and degree of impairment are usually stronger than correlations between urine levels and degree of impairment; however, neither blood nor urine tests are sufficiently accurate to indicate impairment even at high levels of concentration [ 25] , [ 26] , [ 27] . Human studies using marijuana and cocaine have shown that a "perceived high" is reached after the drug concentration has peaked in the blood [ 2] , [ 28] . Generally, blood can only show positive results for a short time after drug consumption, whereas urine can be positive for a few days or weeks after last use. For example, metabolites of THC that are lipid-soluble can be detected in the urine for a few days or for many weeks, depending on the drug habit of the user [ 3] . Excretion of the drug in urine and its concentrations are also effected by several factors, such as dilution and acidity (pH) of the urine. The author has seen many cases where a urine sample was strong positive for cannabinoids in the morning, borderline positive in the afternoon and strong positive the next morning. The author has made similar observations for phenobarbital.

From a positive urine test, the form in which the drug was originally taken or when and how much was taken cannot be determined. For example, crack, impure cocaine powder or cocaine paste (which can be smoked, inhaled, injected or chewed) all give the same result in a urine test. The consumption of poppy seeds has been reported-to give positive results for opiate use because some seeds contain traces of opiates and some have been known to be contaminated with opium derivatives [ 12] . Similarly, consumption of herbal cocoa tea has resulted in positive results for cocaine use. These incidents clearly illustrate the difficulties involved in measuring impairment using urine test results.

The problem of interpreting urine test results is one of the main arguments for restricting their use in the employment setting. In a recent study [ 29] , the effectiveness of pre-employment drug-screening tests has been questioned because of difficulties in interpretation. Based on their analysis of 2,229 pre-employment drug-screening tests and follow- up, Ryan, Zwerling and Jones [291 concluded: 'Our findings raise the possibility that a pre-employment drug screening may be decreasingly effective in predicting adverse outcomes associated with marijuana use after the first year of employment.' They made a similar comment about cocaine.

There is no threshold for alcohol effects on performance or motor vehicle accident risk. Although the effects of alcohol on impairment and crash risk appear more dramatically above 80 mg/100 ml (0.08 per cent), a review of the literature [ 30] , [ 31] would suggest that impairment may be observed at levels as low as 15 mg/100 ml (0.015 per cent). It is not possible to specify a blood alcohol concentration.(BAC) level above which all drivers are dangerous and below which they are safe or at "normal" risk [ 31] .

"Legal" BAC levels differ in different countries. Some even have more than one legal limit over which the driver of a vehicle is considered "impaired". Some European countries have 50 mg/ 100, ml (0.05 per cent) as their legal limit and others have 80 mg/ 100 ml (0.08 per cent). In the United States, the legal limit varies from 80 mg/ 100 ml (0.08 per cent) to 100 mg/100 ml (0.10 per cent) in different states, but employees who are regulated by the United States Department of Transportation have a BAC legal limit of 40 mg/ 100 ml (0.04 per cent). In Canada, there are also two limits, 50 mg/100 ml (0.05 per cent) and 80 mg/100 ml (0.08 per cent); BAC levels between 50 mg/100 ml and 80 mg/100 ml (0.05-0.08 per cent) may result in suspension of driving privileges and levels above 80 mg/100 ml (0.08 per cent) may result in criminal charges.

V. Urine-testing methods

Urine is the most commonly used fluid for drug screening [ 32] . The methods most commonly used in toxicology laboratories are as follows:

  1. Immunoassay:

  2. Enzyme immunoassay (EIA);

  3. Enzyme-multiplied immunoassay technique .(EMIT);

  4. Fluorescence polarization

  5. Radioimmunoassy (RlA);

  6. Chromatography.

  7. Thin-layer chromatography (TLC)

  8. High-performance liquid chromatography (HPLC);

  9. Gas chromatrography (GC.);.

  10. Chromatography coupled with mass spectrometry:

  11. Gas chromatography coupled with mass spectrometry (GC/MS);

  12. High-performance liquid chromatography coupled with mass spectrometry (HPLC/MS).

The methods vary considerably with respect to -their sensitivity and reliability. TLC. is the least expensive and is reliable., GC/MS is considered nearly perfect, or a "gold standard", [ 33] ; it requires highly trained technologists and the most expensive. equipment.

A. Immunoassay

Immunoassay methods are used for preliminary screening (i.e. initial screening). Since the methods are based on an antibody-antigen reaction, small amounts of the drug or 'Metabolite(s) can be detected. Antibodies specific to A particular drug are produced by injecting laboratory animals with the drug. These antibodies are then tagged with markers such as an enzyme (EIA), radio isotope (RIA) -or a fluorescence ((fluorescence polarization immunoassay (FPIA)) label. Reagents containing the labelled antibodies can then be introduced into urine samples and, if the specific drug against Which the antibody was made is present,, a reaction will occur. RIA is the oldest immunoassay method used to detect drugs. The major drawback of this method is that it requires a separation step and generates radioactive waste. RIA also requires special equipment far measuring radioactivity.

Immunoassays typically are designed for a class of drugs. Thus, their specificity (the ability to detect the presence of a specific drug) is not very good as substances that have similar chemical structures will "cross-react" and give a false-positive reaction. For example, the immunoassay method for cannabinoids was developed to detect the carboxylic acid metabolite of THC. Rollins, Jennison and Jones [ 34] , however, showed that non-steroidal anti-inflammatory drugs, ibuprofen (a non-prescription drug in Canada) and, naproxyn can give random or sporadic false positives for cannabinoids. Codeine will also give a positive reaction for the morphine (a metabolic product of heroin use) immunoassay and many antihistamines that are available over the counter may yield positive reactions for amphetamines. While some reagent manufacturers claim to have overcome many of these cross- reactivity problems, confirmation by a non-immunoassay is important. Immunoassays are considered good screening tests but not sufficient by themselves for a conclusion to be drawn. A non-immunoassay method is required to draw a conclusion.

Urine drug assay kits have been available in North America for the past few years. More recently, single- and multiple-test immunoassay kits designed for home and on-site testing have also been introduced. Such kits generally carry a cautionary disclaimer that positive test results must be confirmed by GC/MS, the reference method. When used in a non-laboratory environment, they are prone to procedural inaccuracies, poor quality control, abuse and misinterpretations. Therefore, they are not recommended for testing in the workplace. The risk of labelling a person with a false positive is high without confirmatory analysis. In addition, confirmation analysis is generally expensive when an individual sample is being tested. The advantages and disadvantages of immunoassay testing may be summarized as follows.

  1. Advantages:

  2. Screening tests can be done quickly because automation and batch processing are possible;

  3. Technologists doing routine clinical chemistry testing can be easily trained;

  4. Detection limits are low and can be tailored to meet the programmes screening requirements. For example, lower detection thresholds can be raised to eliminate positives resulting from passive inhalation of marijuana smoke;

  5. Immunoassays are relatively inexpensive, although the single-test immunoassay kits can be expensive when quality-assurance and quality-control samples are included;

  6. Immunoassays do not require a specialized laboratory. Most clinical laboratories have automated instruments to do the procedures;

  7. Disadvantages:

  8. Although the tests are useful for detecting classes of drugs, specificity for individual drugs is weak;

  9. Since the antibody is generated from laboratory animals, there can be a lot-to-lot or batch-to-batch variation in the antibody reagents;

  10. Results must be confirmed by another non.-immunoassay method;-,,

  11. A radioactive isotope is used in RIA that requires compliance with special licensing procedures, use of gamma counters to measure radioactivity and disposal of the radioactive waste;

  12. Only a single drug can be tested for at one time.

B. Chromatography

Separation of a mixture is the main outcome of the chromatographic method. If a drop of ink is put on a blotting paper and the tip of the .paper is held in water, the water will rise in the paper. After a period of time and under the right conditions, the single ink spot will separate into many different compounds (spots) of different colours (blue ink is a mixture of many dyes). This process, whereby a mixture of substances is separated in a stationary medium (filter paper), is called chromatography. The types of chromatographic processes used in the analysis of drugs .include thin-layer, gas, and liquid chromatography as well as a combination of gas or liquid chromatography with mass spectrometry.

1. Thin-layer chromatography

TLC is most similar to the ink separation example mentioned above. This method requires extensive sample preparation and technical expertise on the part of the analyst, but it is inexpensive and powerful if used properly. With the exception of cannabis, which requires separate sample preparation, a large number of drugs (e.g. cocaine, amphetamine, codeine and morphine) can be screened at the same time. By combining different

TLC, systems, a high degree of :specificity. can be obtained, although the training of the analyst is crucial because of the subjectivity involved in interpreting the results. To identify positive TLC "spots", the technologist looks for the drugs and/or their metabolite patterns. A trained technologist can identify more than 40 different drugs.

2. Gas chromatography

GC, which is similar to TLC, requires extensive sample preparation. In GC, the sample to be analysed is introduced into a narrow bore (capillary) column with a syringe. The. column, which sits inside an oven, is flushed with a carrier gas such as helium or nitrogen. In a GC system that has been properly set up, a mixture of substances introduced into the carrier gas is volatilized and the individual components of the mixture migrate through the column at different speeds. Detection takes place at the end of the heated column. and is generally a destructive process. Often, the substance to be analysed is "derivatized" to make it volatile or to change its chromatographic characteristics.

3. High-performance liquid chromatography

In contrast to GC, high-performance liquid chromatography (HPLC) requires a liquid under high. pressure, rather than a gas, to be used to flush the column. Thus, this technology is sometimes referred to as high - pressure liquid chromatography. Typically, the column operates at room temperature or slightly above room temperature. This method is generally used for substances that are difficult to volatilize (e.g. steroids) or are heat-labile (e.g. benzodiazepines). The two major differences between GC and HPLC are as follows:

  1. GC is a "destructive" method (it destroys or burns the chemical in its detector to generate the signal), whereas HPLC detection takes advantage of the electronic or chemical structure of the compound;

  2. The mobile phase in GC is gas; in HPLC it is liquid. Consequently, less sample preparation is needed for HPLC. HPLC also has high specificity, but it is slower and generally less sensitive than GC.

C. Gas chromatography coupled with mass spectrometry

GC/MS is a combination of the two sophisticated technologies. GC physically separates (chromatographs or purifies) the compound, and MS fragments it so that a fingerprint of the chemical (or drug) can be obtained. Although sample preparation is extensive, when the methods are used together the combination is regarded by most authorities as the "gold standard'. This combination is sensitive (it can detect low levels), specific and able to identify all types of drugs in any body fluid. Furthermore, assay sensitivity can be enhanced by treating the test sub- stance with reagents. When coupled with MS, HPLC/MS is the method of choice for substances that are difficult to volatilize (e.g. steroids).

Given the higher costs associated with GC/MS, urine samples are usually tested in batches for broad classes of drugs by immunoassay, and positive screens are later subjected to confirmation by this more expensive technique. This is the most common approach used in employment drug- screening programmes and is the combination recommended by NIDA [ 13] in the United States.

The advantages and disadvantages of the various methods of chromatographic drug testing are as follows:

  1. Advantages:

  2. All chromatographic methods: All the chromatographic methods are specific and sensitive and can screen a large number of drugs at the same time;

  3. TLC: Negligible capital outlay is needed;

  4. GC: The procedure can be automated;

  5. HPLC:

    a. Of the chromatographic procedures, it has the easiest sample preparation requirements; b. The procedure can be automated;

  6. GC/MS:

    a. It is regarded as the "gold standard" test; b. Computerized identification of fingerprint patterns makes identification easy; c. The procedure can be automated; d. It is currently the preferred method for defence in the legal system;

  7. Disadvantages:

  8. All chromatographic methods: All the chromatographic methods are labour-intensive and require highly trained staff. Although all the chromatographic methods are specific, confirmation is still desirable;

  9. TLC: Interpretation is subjective, hence training and experience in interpretation capabilities of the technologist are crucial;

  10. GC or HPLC: Equipment costs are high, ranging between US$ 25,000 and US$ 60,000, depending on the type of detector and automation selected;

  11. GC/MS:

    a. Equipment costs are the highest, ranging from US$ 120,000 to US$ 200,000, depending on the degree of sophistication required; b. Due to the complexity of the instrument, highly trained operators and technologists are required.

Table 2 presents a comparison of all the methods of testing.

Table 2. Comparison of all drug testing methods

Aspect

EMIT and FPIA

RIA

TLC

GC and HPLC

GC/MS

Ease of sample preparation
x
x
 
x
 
Less highly trained technologists required
x
x
     
Limited equipment required
x
x
x
   
Low detection limits
x
x
x
x
x
Adjustable lower threshold
x
x
     
Highly specific and sensitive
   
x
x
x
Computerized identification possible
       
x
Screen for several drugs at a time
   
x
x
x
Procedure can be automated
x
x
 
x
x
Special atomic energy licence required
 
x
     
Confirmation of results required
x
x
x
x
 
Interpretation is subjective
   
x
   
Notes:
         
EMIT
=
enzyme-multiplied immunoassay technique
FPIA
=
fluorescence polarization immunoassay
GC
=
gas chromatography
GCIMS
=
gas chromatography coupled with mass spectrometry
HPLC
=
high-performance liquid chromatography
RIA
=
radioimmunoassay
TLC
=
thin-layer chromatography

D. Procedures for alcohol testing

Since the introduction by Widmark [ 35] in 1922 of the "micro-method" for alcohol analysis in blood, many new methods and modifications have been introduced. The distillation/oxidation methods are generally non-specific for ethanol [ 36] , [ 37] , whereas biochemical (spectrophotometric) methods using alcohol dehydrogenase (ADH) obtained from yeast [ 38] and the gas chromatographic [ 39] method that are currently in use are specific for ethanol. The radiative energy attenuation technique [ 40] and those using the alcohol oxidase method are non-specific and will detect not only ethanol but also other alcohols. The recently introduced alcohol dipstick [ 41] , based on the ADH enzyme system, is not only specific for ethanol, but also sensitive and does not require instrumentation. It can be used for the detection of ethanol in all body fluids and can provide semi-quantitative results in ranges of pharmacological-toxicological interest. The alcohol dipsticks are being used in many alcohol treatment programmes as well as in a number of laboratories as a screening device.

Breath can be analysed using a variety of instruments. Most of, the instruments used today detect ethanol by using, for example, thermal conductivity, colorimetry, infrared spectroscopy or gas chromatography. In most countries, local statutes define the instrument and method that can be used for evidentiary purposes. A variety of Breathalyser instruments, the prices of which range from US$ 100 to US$ 1,000, are available. The instruments are compact and portable. The Canadian law enforcement authorities use as a roadside alcohol-screening device a Breathalyser instrument that gives a "pass" or "fail" result. A person who fails that test is generally subjected to a Breathalyser test to measure the BAC level before any charges are made. Many devices are available to preserve the breath sample for later analysis if a Breathalyser is not available immediately. In forensic laboratories in North America, gaschromatographic procedures are used to analyse biological samples; in many European countries, biochemical procedures are used.

Blood samples that cannot be analysed soon after collection, should have sodium fluoride (NaF) added as a preservative [ 42] . ADH, the enzyme responsible for the oxidation of alcohol, is also present in red blood cells and will slowly metabolize the alcohol, causing its concentration to drop if the preservative is not added. Large amounts of alcohol can be produced in vitro in the urine samples of diabetic patients if samples are not processed immediately.

VI. Interpretation of test results

A. False negatives

A positive or negative result is highly dependent on the sensitivity of the drug detection method. A false negative occurs when the drug is present but is not found because the detection limit of the method used is too high or the absolute quantity of the drug in the specimen is too low.

Large amounts of fluids consumed prior to obtaining a sample for analysis can affect detection of drugs in urine samples. Under conditions of dilution, although the absolute amount of drug or metabolite excreted may be the same over a period of time, the final concentration per millilitre will be reduced and may give a false-negative result. Acidity levels in the urine may also affect the excretion of the drug into the urine. In some cases, elimination is enhanced; in others, the drug is reabsorbed.

Several measures can be used to decrease the likelihood of obtaining a false-negative result. First, sensitivity of the method can be enhanced by analysing for the metabolites of the drug in question. Heroin use, for example, is determined by the presence of the heroin metabolite, morphin. Increasing the specimen volume used for analysis or treating it with chemicals can also make laboratory methods more sensitive. Studies in the author's laboratory have shown that one 5 mg dose of valium is usually detected for 3-4 days. When these improved methods are utilized, however, sensitivity can be increased so that the same dose can be detected for up to 20 days. One significant drawback of such high sensitivity is that estimates of when the drug was taken are far less accurate.

B. False positives

A false positive occurs if results show that the drug is present when in fact it is not. False-positive tests are obtained if an interfering drug -or substance is present in the biological fluid and it cross -reacts with the reagents. As discussed in the previous section on immunoassays, an initially positive test based on immunoassay technique should always be con - firmed with a non-immunoassay method. A confirmed positive finding only implies that the urine sample contains the detected drug and nothing more.

Sometimes false positives are attributable to ingested substances such as asthma or allergy medication [ 43] . Some authors have suggested that employees subject to drug screening should refrain from using certain brands of over-the-counter medication because they have caused false positives [ 44] . Some natural substances such as herbal teas and poppy seeds can also give positive responses to screens., These may be analytically true positives but they need to be distinguished from those due to illegal drug use. In some instances, false positives have been the result of mistakes or sabotage in the chain of custody for urine samples.

VII. Common adulteration methods

Substituting "clean" or drug-negative urine for drug-positive urine is the most common way to fool the drug-screening system. A number of entrepreneurs have attempted to bypass urine sample inspection in this manner. A company in Florida sells lyophilized (freeze-dried) "clean" urine samples through newspaper and magazine advertisements. Hiding condoms containing "clean" urine on the body or inside the vagina is another common trick. Recently, a patient at an addiction research clinic was, caught substituting "clean" urine when a glass bottle that had fallen into the toilet bowl was discovered by the supervising nurse. It was later discovered that the bottle had been sealed with a thin aluminium wrap and had been inserted into the patient's vagina.

Others have attempted to substitute apple juice or tea for urine samples. Persons have been known to add to urine samples various house - hold products, ranging from bleach to liquid soap to eye-drops, hoping that their drug use would be masked. Others have hidden a masking substance under their fingernails and released it into the urine specimen. Another method is to poke a small hole into the urine sample container with a pin so that the sample leaks out by the time it reaches the laboratory [ 45] .

Since adding table salt (NaCl) or bleach to urine samples is a common practice, many laboratories routinely test for sodium and chlorine in urine samples. Liquid soap and crystalline drain cleaners, strong alkaline products containing sodium hydroxide (NaOH), are also used to adulterate urine samples. These contaminators can be detected by checking for high pH levels in urine samples. In vivo alkalizing or acidifying the urine pH can also change the excretion pattern of some drugs, including amphetamines, barbiturates and PCP.

Water-loading (drinking large amounts of water prior to voiding) poses an interesting challenge to testing laboratories. Specific gravity has been used to detect dilution; however, the measurement range is limited. Creatinine levels in random urine samples have also been studied as a possible water-loading detection method, but without much success.

Drug-using patients are resourceful and their ingenuity should not be underestimated. In order to reduce the opportunities for specimen contamination, some workplaces require that employees provide urine samples under direct supervision. Another way to detect any sample adulteration is to take the temperature of the sample. When the temperature of samples are taken within one minute of voiding, the temperature range falls to between 36.5¦deg; and 34¦deg; C, reflecting the body core temperature. It is difficult to achieve this narrow temperature range by hiding a condom filled with urine in the armpit or adding water from a tap or toilet bowl to the urine sample. The temperature of the sample must be measured immediately after it is taken, since the temperature drops rapidly.

VIII. Laboratory procedural and security standards

It is important that the laboratory drug testing facility has qualified individuals who follow a specific set of laboratory procedures and meet certain security standards. Laboratory management personnel must have documented qualifications in analytical forensic toxicology in order to analyse urine samples for the presence of drugs [ 46] . A flow chart showing the various steps in the drug-testing process, from sample collection to the final disposition of the results, is provided in figure I. Figure II shows the space, staffing and equipment requirements.

The laboratory should be secure at all times and access should be limited to authorized individuals only. The laboratory should establish security measures to guarantee that specimens are properly received, documented, processed and stored. Documentation of chain-of-custody procedures should include specimen receipt, results during storage and final disposition of specimens. The laboratory must comply with any governmental licence requirements, must be inspected routinely, must keep appropriate documentation and procedural manuals and must use properly certified equipment.

Urine specimens should be inspected immediately upon arrival at the laboratory in order to ensure that they have -not been tampered with during delivery. Specimens should be stored in a secure refrigeration unit if they are not tested within seven days of arrival at the laboratory. The storage temperature should not exceed 6¦deg; C. Long-term storage must be at -20¦deg; C to ensure that positive urine specimens will be available for any retesting during administrative or disciplinary proceedings. The laboratory will be required to maintain any specimen under legal challenge for an indefinite period.

Figure I. Schematic representation of the drug-testing process

Full size image: 98 kB, Figure I. Schematic representation of the drug-testing process

Figure II. Space and staffing requirements of the drug-testing process

Full size image: 116 kB, Figure II. Space and staffing requirements of the drug-testing process

IX. Initial and confirmatory testing requirements

The initial test (i.e. screening test) consists of an immunoassay technique that meets the requirement for commercial distribution and eliminates "negative" urine specimens from further consideration. Minimal (cut-off) levels should be used when screening a specimen to determine whether it is negative. Some negative cut-off levels (in nanograms per millilitre) for initial tests are as follows [ 13] :

The initial test (i.e. screening test) consists of an immunoassay technique that meets the requirement for commercial distribution and eliminates "negative" urine specimens from further consideration. Minimal (cut-off) levels should be used when screening a specimen to deter- mine whether it is negative. Some negative cut-off levels (in nanograms per millilitre) for initial tests are as follows [13]:

Tetrahydrocannabinol metabolite
100
Cocaine metabolite
300
Opiate metabolites
300 a/
PCP
25
Amphetamines
1,000
Alcohol (mg/100ml)
10
a/ If immunoassay is specific for free morphine, 25 nanograms per millilitre.

In the event of an identified positive, on the initial test, a confirmatory test should be performed, whereby a second and different analytical procedure is used to identify the presence of a specific drug or metabolite. At present, GC/MS is the recommended confirmation method. Some minimal (cut-off) concentrations (in nanograms per mililitre) for confirmatory tests are as follows [ 13] :

In the event of an identified positive, on the initial test, a confirmatory test should be performed, whereby a second and different analytical procedure is used to identify the presence of a specific drug or metabolite. At present, GC/MS is the recommended confirmation method. Some minimal (cut-off) concentrations (in nanograms per mililitre) for confirmatory tests are as follows [13]:

Tetrahydrocannabinol metabolites a/
15
Cocaine metabolites b/
150
Opiates
 
Morphine
300
Codeine
300
PCP
25
Amphetamines
 
Amphetamine
500
Methamphetamine
500
Alcohol (mg/100 ml)
10

a/ For example, 11-nor-Δ-9terahydrocannabinolic acid.

b/ Benzoylecgonine.

X. Regulations for drug testing *

The purpose of the regulations is to detail the standards and procedures of laboratories that plan to provide drug testing for the work-place. There are two main parts to the present section. The first part describes the requirements for the site collection of urine samples and the second documents the essentials of laboratory drug testing [ 47] .

Extreme caution must be exercised in the testing procedures. Using specimens for other types of analysis such as pregnancy or other disease criteria is expressly prohibited. In addition, the possible impact of a positive result on an individual's livelihood or rights, together with the possibility of a legal challenge of the results, sets this type of testing apart from most clinical laboratory analysis. Urine drug testing should be considered a special application of analytical forensic toxicology. That is, in addition to the application of appropriate analytical techniques, the specimens must be treated as evidence and all aspects of the testing procedure should be documented and available for examination.

A. Specimen collection procedures

The purpose of the present subsection is to outline the procedures used to ensure integrity of the specimens during urine collection and during their transportation to a laboratory. A proper urine specimen collection is the key to developing a successful testing programme.

The first concern of specimen collection is designating a specimen collection site. The collection site must have all the personnel, material, equipment and supervision necessary to allow the sample to be collected, temporarily stored and transported to the drug-testing facility. Collection site personnel must have successfully completed training to carry out these functions.

A second concern is ensuring the security of the collection site. If the collection site facility is used solely for urine collection, it should be secured at all times and accessible only to authorized persons. When urine sample specimens are being collected or stored, no unauthorized individual should be permitted in any part of the designated collection site unless he or she is accompanied by an authorized person.

*The protocols and procedures in the present section are based on the accumulated knowledge of the author in his capacity as Inspector for the College of American Pathologists (CAP), a certifying agency for drug-testing laboratories in the United States. In addition, guidelines suggested by Kwong and others [ 46] , CAP [ 47] , NIDA [ 13] and the Canadian laboratory standards for drug screening in the workplace were extensively consulted.

Procedures for collecting urine samples should allow for individual privacy unless there is reason to believe that a particular individual may alter or substitute a sample to be provided.

1. Minimal procedures to ensure integrity and identity of specimens

The following minimal procedures should be followed to ensure the integrity and identity of the specimen at the collection site, to help to safeguard against specimen adulteration or dilution during the collection procedure and to allow for proper identification of the individual being tested:

  1. Immediately after the specimen is collected, the collection site person should also inspect the specimen to determine its colour and should took for any signs of contaminants. Any unusual findings should be noted in a permanent record or logbook;

  2. All specimens suspected of being adulterated should be forwarded to the laboratory for testing;

  3. Both the individual being tested and the collection site person should keep the specimen in view at all times prior to it being sealed and labelled. If the specimen is transferred to a second bottle, the collection site person should request the individual being tested to observe the transfer of the specimen and the placement of a tamper-proof seal over the bottle cap and down the side of the bottle;

  4. The collection site person should securely place an identification label on the bottle that contains the date, the individual specimen number and any other identifying information provided or required- by the laboratory;

  5. The individual being tested should identify the label on the specimen bottle to certify that the specimen was. actually collected from him or her;

  6. The collection site, person should, enter into the permanent record or logbook all information identifying the specimen. The collection site person should then sign the permanent record or logbook next to the identifying information. An individual being tested should be asked to read and sign a statement in the permanent record or logbook certifying that the specimen identified was collected from him or her;

  7. The collection site person should complete the chain-of-custody form;

  8. If the specimen is not immediately prepared for shipment, it should be appropriately safeguarded during temporary storage in a refrigerator at a temperature of about 4¦deg; C. The specimen should normally be shipped within 48 hours and definitely no longer than one week after it has been placed in storage. If stored longer, the temperature should be -20¦deg; C;

  9. In the event that a collection site is not accessible and there is immediate requirement for specimen collection (e.g. an accident investigation), a public rest room may be used according to the following procedures:

  10. A collection site person of the same gender as the individual being tested may accompany the individual into the public rest room, which shall be made secure during the collection procedure;

  11. If possible, a toilet bluing agent should be placed in the toilet bowl and any accessible toilet tank to deter specimen dilution. If no bluing agent is available, the collection site person should instruct the individual; being tested not to flush the toilet until the specimen is, delivered to the collection site person;

  12. It is essential that the urine specimen and the custody document be under the control of the collection site person. If the collection site person leaves the workstation for a short period, the specimen and the chain-of-custody form should be taken with him or her or should be secured. After the collection site person returns to the workstation the custody process should continue. If the collection site person leaves the site for an extended period of time, the specimen should be packaged for transportation beforehand;

  13. Collection control site personnel should keep the specimen bottle within sight both before and after the individual has urinated. After the specimen is collected, it should be properly sealed and labelled and an approved chain-of-custody form should be used to control and account for each specimen from the point of collection to final disposition of the specimen;

  14. The date and purpose should be documented on an approved chain-of-custody form each time a specimen is handled or transferred and every individual in the chain of custody should be identified. Every effort should be made to reduce to a minimum the number of persons handling the specimen;

  15. Collection site personnel should arrange to ship the collected specimen to the drug -testing laboratory (see the subsection below entitled "Guidelines for transporting specimens"). Specimens should be placed in a container designed to keep to a minimum the possibility of damage during shipment. Specimen boxes or padded mailers, for example, should be securely Scaled to eliminate the possibility of undetected tampering. On the tape used to seal the container, the collection site supervisor should place his or her signature and enter the date on which the specimen is being scaled for transportation. Collection site personnel should ensure that the chain-of-custody document is-attached to each container and is being sealed for shipment to the drug-testing laboratory.

2. Procedures to maintain the integrity of specimens

The following procedures are recommended to ensure that unadulterated specimens are obtained:

  1. An individual being tested should be instructed to wash and dry 'his or her hands prior to urination. After washing his or her hands, the individual being tested should remain in the presence of the collection site person and should not have access to any water fountains, faucets, soap dispensers, cleaning agents or any other material that could be used to adulterates the specimen;

  2. The collection site person should note any unusual behaviour or appearance of the individual being tested in the permanent record or logbook;

  3. To deter: dilution of the specimen at the collection site, toilet bluing agents should be placed in toilet tanks whenever possible so that the reservoir of water in the toilet bowl always remains blue. Ideally, there should lie no source of running water (i.e. no sink in the room where the urine is collected);

  4. The individual giving the urine sample should be requested to remove any unnecessary outer garments, such as a coat or jacket or hand- bag, that might conceal items or substances that could be used to tamper with or adulterate the urine sample;

  5. Upon receiving the sample from the individual, the person supervising the collection should determine whether it contains a minimum of 60 ml of urine. If there is less than 60 ml of urine in the container, then an additional urine sample should be collected in a separate container. The individual being tested may be given a reasonable amount of liquid to drink for this purpose;

  6. After the specimen has been submitted to the person supervising the collection, the individual being tested should be allowed to wash his or her hands;

  7. Immediately after the specimen is collected, the person supervising the collection shall measure and record the temperature of the specimen. The time from urination to temperature measurement is critical and in no case should exceed four minutes. Normal temperature ranges from 32.5¦deg; to 37.7¦deg; C (90.5¦deg;-99.8¦deg; F). (In the author's laboratory, temperatures of 100 consecutive urine samples ranged between 34.5¦deg; and 36.5¦deg; C when measured within two minutes of voiding.);

  8. If the temperature of the specimen is outside the range of 32.5¦deg;-37.7¦deg; C (90.5¦deg;-99.8¦deg; F) or the pH is not between 4.8 and 8, there is reason to believe that the individual being tested may have altered or substituted the specimen and another specimen should be collected under direct observation by the collection site person. Both specimens should be identified and forwarded, with appropriate comments, to the laboratory for testing. The individual being tested may volunteer to have his or her body temperature taken to refute the suggestion that the specimen was altered or substituted. Diluted urine can also be detected by its pale colour or by its smell if adulterants such as ammonia or furniture polish have been added;

  9. Immediately after the specimen is collected, the collection site person should also inspect the specimen to determine its colour and to look for any signs of contaminants. Any unusual findings should be recorded in the permanent record or logbook;

  10. All specimens suspected of adulteration should be forwarded, with appropriate comments, to the laboratory for testing;

  11. It is important that the sample container is properly labelled before it is given to the individual being tested. Ideally, the scaling of the specimen container should be witnessed by the individual being tested.

3. Guidelines for transporting specimens

To maintain effective control while transporting the urine sample to the testing laboratory, the following guidelines for transporting specimens should be kept in mind:

  1. All containers (i.e. plastic urine bottles) must be checked for cracks before filling, and only intact containers should be used;

  2. Chain-of-custody forms and containers must be clearly labelled;

  3. Appropriate protective equipment must be worn to maintain body substance precaution techniques during retrieval of all specimens;

  4. All specimen caps or lids should be checked before transporting to see if they are securely closed;

  5. Specimen containers should be placed in the designated transportation container;

  6. Specimens should always be handled carefully to avoid breakage.

B. Laboratory procedures

Laboratory personnel requirements

Laboratory management personnel must have documented qualifications in analytical forensic toxicology in order to carry out the analysis of urine samples for drug testing. They must be able to review data and quality-control results, to supervise the routine operations of drug testing, to train personnel and to keep files on personnel.

The laboratory should have a qualified director to assume the professional, organizational, educational and administrative responsibilities for its urine drug-testing facility. That individual should have documented scientific qualifications in analytical forensic toxicology. The minimum qualifications are as follows:

  1. A Doctor of Philosophy (Ph.D.) in one of the natural sciences and an adequate undergraduate and graduate education in biology, chemistry and pharmacology or toxicology; or training and experience comparable to a Ph.D. in one of the natural sciences such as a medical or scientific degree with additional training and laboratory research experience in biology, chemistry and pharmacology or toxicology;

  2. Appropriate experience in analytical forensic toxicology, including experience in the analysis of biological materials for drugs of abuse;

  3. Appropriate training and or experience in forensic applications of analytical toxicology (e.g. publications, court testimony, research concerning analytical toxicology of drugs of abuse or other factors that qualify an individual as an expert witness in forensic toxicology).

In jurisdictions where certification as a laboratory director is required, the director should be certified or be eligible to apply for that certificate. The director will be responsible for certifying the final test results being reported.

The laboratory urine drug-testing facility should have qualified individuals who review all pertinent data and quality- control results in order to attest to the validity and certification of the laboratory test reports. The laboratory may designate more than one person to perform this function. Such individuals may be any employees who are qualified to be responsible for the day-to-day management or operation of the drug- testing laboratory. Individuals responsible for the day-to-day operations and supervision of the technical analysis should at least have Bachelor's degrees in chemical or biological sciences or medical technology or the equivalent. They should have training and experience in the theory and practice of procedures used in the laboratory and should thoroughly understand quality-control practices and procedures. They will be responsible for reviewing, interpreting and reporting test results and for maintenance of the chain of custody. Additionally, these individuals should ensure that proper remedial actions are taken in response to test systems that are out of control limits or when erroneous results are detected.

Other technical and non-technical staff should have the necessary training and skills for the tasks that they will be assigned. The laboratory programme should make continuing education programmes available to meet the needs of the laboratory, professionals., The personnel file of such an individual should include the following:

  1. A rsum or documentation of training and experience;

  2. Certification and licence, if any;

  3. References;

  4. Job descriptions;

  5. A record of performance evaluation and advancement;

  6. Incident reports and results of tests that establish employee competence and advancement.

2. Laboratory security and chain of custody

The laboratory should be secure at all times. Sufficient security measures should be in place to control access to the premises and to ensure that no unauthorized personnel handle specimens or gain access to the laboratory processes or the record or log storage areas. Access to these secured areas should be limited to specifically authorized and documented individuals. With the exception of personnel authorized to conduct inspections, all visitors and maintenance service personnel should be escorted at all times. Records of individuals entering these areas and the date, time and purpose of entry must also be maintained. Documentation of chain -of -custody procedures should include specimen receipt, results during storage and final disposition of specimen. The date and purpose should also be documented on an appropriate chain-of-custody form each time the specimen is handled or transferred, and every individual in the chain should be identified. Accordingly, authorized technologists should be responsible for each urine specimen in their possession and must sign a complete chain-of-custody form when such specimens are received.

The drug-testing laboratory must have security measures to guarantee that specimens are properly received, documented, processed and stored. The laboratory must also comply with any governmental licensing requirements,. must be inspected routinely, must keep appropriate documentation and procedure manuals and must use properly certified equipment.

3. Receiving specimens

When a shipment or specimen is received, the laboratory personnel should inspect each package for evidence of tampering and should compare information on specimen bottles with each package of information accompanying the chain-of-custody forms. Any direct evidence of tampering or discrepancy between the information on the specimen bottle and the accompanying chain-of-custody form should be recorded on the chain-of-custody form and accompany the specimen while it is in the laboratory. Specimen: bottles should normally be retained within the laboratory area until all analyses have been completed.

4. Storing specimens

Specimens that do not receive an initial test within seven days of arrival at the laboratory must be placed in a secure refrigeration unit. The temperature must not exceed 6¦deg; C. Emergency electrical power equipment should. be available in case of prolonged power failure.

Long-term storage must be at a temperature of 20¦deg; C-to ensure that positive urine specimens are available for any retesting during administrative or disciplinary proceedings. Unless otherwise authorized in writing, the laboratory must retain and place in properly secured long- term storage all specimens confirmed positive for a minimum of one year. Within this one-year period, the client may request the laboratory to retain the specimen for an additional period of time. If no such request is received the laboratory should discard the specimen after one year. The laboratory will be required to maintain any specimen under legal challenge for an indefinite period.

5. Initial and confirmatory testing

Specimens can be processed in batches for either initial or confirmatory toasts. When conducting either initial or confirmatory tests, every batch should contain an appropriate number of standards for calibrating the instrument and a minimum of two specimen controls or 10 per cent specimen controls, whichever is higher. Both quality-control and blind performance test samples will appear as ordinary samples to the laboratory analyst.

The initial test (screening test) involves an immunoassay technique that meets the requirement for commercial distribution and eliminates a "negative" urine specimen from further consideration. The initial cut-off levels (see the section above entitled "Initial and confirmatory testing requirements') should be used when screening a specimen to determine whether it is negative for the drugs or classes of drugs being tested. For alcohol, the initial test may be an enzymatic test based on the ADH system.

In the event of an identified positive on the initial test, a confirmatory test in which a second analytical procedure is used to identify the presence of a specific drug or metabolite must be performed. The confirmatory test method must use a different technique and chemical principle from that of the initial test. At present, GC/MS is the recommended confirmation method for reasonable analytical accuracy of cocaine, marijuana, opiates, amphetamines and PCP. In the case of alcohol, confirmation must be done by using a gas chromatographic procedure. The values obtained by the initial test and the confirmatory test for alcohol must be within 10 per cent of each other. All confirmations must include quantitative analysis. Concentrations that exceed the linear region of the standard curve should be documented in the laboratory records as greater than the highest standard curve value.

The results of retesting of specimens (being challenged) must confirm the presence of the drug or metabolite in question but are not required to correspond to any specific cut-off level since some analyte may deteriorate during the freezing, thawing or storage procedures.

6. Operational guidelines
(a) Laboratory facilities

The laboratory must comply with provisions of the local governmental licensing requirements. In order to attain certification, the laboratory must be capable of performing both the initial and the confirmatory tests for each drug or metabolite for which the service is being offered. Urine specimens collected for the purpose of drug testing should only be used to test for those drugs included in their clients' approved drug- free workplace plan and may not be used to conduct any other analysis or tests.

(b) Inspection

A certification body or any client utilizing the laboratory may reserve the right to inspect the laboratory at any time. Any employer who has contracted the laboratory for drug testing or collection site services is permitted to conduct unannounced inspections. In addition, prior to awarding a contract, a client may carry out pre-award inspections and evaluations of the procedural aspects of the laboratory drug-testing operation.

(c) Subcontracting

Unless authorized to do so, the drug-testing laboratory may not subcontract and should perform all, work with its own personnel and equipment unless otherwise authorized by the client. If subcontracting is authorized, then the subcontracted laboratory must be capable of performing tests for the agreed upon classes of drugs. Same-site screening and confirmation is ideal for the maintenance of strict quality control in the chain of custody and in transporting and processing samples, as well as in reporting results. The subcontracting laboratory must adhere to the guidelines stated in the present paper.

(d) Information collection requirement

The drug-testing laboratory must maintain and make available for at least two years documentation of all aspects of the testing process. The required documentation must include the following:

  1. Personnel files on all individuals authorized to have access to the specimen;

  2. Chain-of -custody documents;

  3. Quality-assurance and quality-control records;

  4. Operating procedure manuals according to which the tests were performed;

  5. All test results including calibration curves and any calculations used in determining the test results;

  6. Reports;

  7. Performance records on performance testing;

  8. Performance on certification inspections;

  9. Hard copies of any computer-generated results.

(e) Procedure manuals

The laboratory procedure manual must include the following:

  1. The principle of each test;

  2. Preparation of reagents;

  3. Standards and controls;

  4. Equipment set-up and calibration procedures;

  5. Schedule for critical operational checks on equipment;

  6. Derivation of results;

  7. Linearity of methods;

  8. Sensitivity of the methods;

  9. Cut-off values;

  10. Mechanism of reporting results;

  11. Controls;

  12. Criteria for unacceptable specimens and results;

  13. Remedial actions to be taken if test systems are outside acceptable limits;

  14. Reagents and expiration dates;

  15. References.

Copies of all procedures and dates on which they are in effect should be maintained as part of the laboratory procedure manual under the signatory approval of the director of the drug-testing laboratory.

(f) Standards and controls

Laboratory standards should be prepared with pure drug standards that are properly labelled, indicating their content and purity. The standards are to be labelled with the following dates:

  1. Date received;

  2. Date opened or prepared;

  3. Expiration date.

When reagents are prepared, the date and the initials of the person preparing them should be recorded. Control samples should be labelled with a code allowing the analysts to test them in a blind manner. The temperature of the refrigerator used for storing the reagents should be checked and recorded daily. The results for controls and standards must be recorded along with the date, time and name of the analyst conducting the test procedure.

(g) Instruments and equipment

The laboratory, supervisor should oversee the day-to-day maintenance of the laboratory equipment. Volumetric pipettes and other measuring devices must be certified for accuracy or checked by gravimetric, colorimetric or other verification procedures. Automatic pipettes and diluters should be checked for accuracy and reproducibility before being placed in service and should be checked monthly thereafter. The procedure manual should include written procedures for instrument setup, calibration, critical operating characteristics, tolerance limits for acceptable function checks and instructions for major trouble-shooting and repair. Records must also be available on preventative maintenance for the instruments.

(h) Reporting of results.

The laboratory should report results to the medical review officer within an average of 10 working days after receipt of the specimen. Before a test result is reported, it should be reviewed and test-certified as an accurate report by the individual responsible for this activity. The report should identify the drug metabolites tested for (whether positive or negative), cut-off levels, the specimen number assigned by the test- requesting facility and the drug-testing laboratory specimen identification number. The results, whether positive or negative, should be reported back to the medical review officer, at the same time. The laboratory should report as negative all specimens that are negative on the initial test or negative on the confirmatory test. Only specimens confirmed positive should be reported positive for a specific drug. The laboratory must provide quantitative. test results at the request of the medical review officer.

(i) Quality,-assurance and quality-control procedures

The drug-testing laboratory have a quality-assurance and quality-control programme that encompasses all aspects of the testing process, from specimen collection to reporting of the results and the final disposition of the specimen. Quality-assurance procedures should be designed, implemented and reviewed to monitor each step of the process.

The quality-control requirements for initial tests should be structured so that each analytical run of specimen to be screened includes:

  1. A urine specimen certified to contain no drug;

  2. A urine specimen fortified ("spiked") with known standards;

  3. Positive controls with a drug or metabolite at or near the threshold or cut-off level.

In addition, with each batch of samples, a sufficient number of standards should be included to document the linearity of the assay method over time in the concentration range of the cut-off. A minimum of 10 per cent of test samples should be used as quality-control samples.

The quality-control requirements for confirmatory tests should be structured so that each analytical run of specimen to be confirmed includes:

  1. A urine specimen containing no drugs;

  2. A urine specimen fortified ("spiked") with known standards;

  3. A positive and positive controls with a drug or metabolite at or near the threshold or cut-off level.

Linearity and precision of the method must be periodically documented. Implementation of procedures to ensure that carry-over does not contaminate the testing of the individual specimen should also be documented.

7. Review of results
(a) Medical review officer

The medical review officer should be a licensed physician with a knowledge of substance abuse disorders. A positive result does not auto- matically identify an individual as an illegal drug user. The role of the medical review officer is to review, verify and interpret positive test results obtained through the client's drug- testing programme. In carrying out his or her responsibilities, the medical review officer should examine alternate medical explanations for a positive test result by, for example, conducting a medical interview with the individual, reviewing the individual's medical history and determining the clinical evidence of illegal use of any opiate or opium derivatives. The medical review officer should review all medical records available on the tested individual to ascertain whether or not a confirmed positive could be explained by the use of a legally prescribed medication. Prior to making a final decision to verify a positive result, the medical review officer should give the individual an opportunity to discuss the test results with him or her. If the medical review officer determines that there is a legitimate medical explanation for the positive test, the result is consistent with the legal drug use and no further action should be taken.

Should any question arise as to the accuracy or validity of a positive test result, the medical review officer is authorized to order a reanalysis of the original sample. Additionally, based on the review and inspection of reports, quality-control data, multiple samples and other pertinent results, the medical review officer may determine that the result is scientifically insufficient for further action and declare the test specimen negative. The director of the laboratory should be available to consult with the medical review officer as required. The employee being tested has a right to identify a prescribed medication when the urine sample is being provided.

(b) Protection of employee records

All laboratory contracts should require that the contractor comply with the privacy act. In addition, the laboratory contract should require compliance with the access and confidentiality provisions established within the jurisdiction where the laboratory practice is maintained. The contract and the privacy act should specifically require that employee records be maintained and used with the highest regard for employee privacy.

(c) Individual access to test results and laboratory certification results

Any employee who is subject to drug testing should, upon written request, have access to any records relating to his or her drug test and any records relating to the results of any relevant certification review proceedings.

8. Certification of laboratory

The laboratory must meet all pertinent provisions and guidelines stated in the present paper. In determining whether to certify a laboratory or to accept the certification, the following criteria should be considered:

  1. The adequacy of the laboratory facilities;

  2. The expertise and experience of the laboratory personnel;

  3. The level of the laboratory's quality-assurance and quality-control programme;

  4. The performance of the laboratory on annual performance tests (once in place);

  5. The laboratories compliance with the standards as reflected in any laboratory inspection;'

  6. Any other factors affecting there liability and accuracy of drug tests and reporting done by the laboratory.

In order to remain certified the laboratory must participate in blind drug-testing challenges initiated by the certifying body. During the process, 90 per cent of the number of tests performed must be correctly identified (i.e. identification and confirmation of 90 per cent of the total drug challenges) or suspension or revocation of the certificate may take place.

References

00

Thin-layer chromatography

01

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02

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