Assessment

Biological markers of drug useKim Wolff

Abstractthe variety of different body matrices that can be analysed to determine

the presence or absence of different psychoactive substances is exten-

sive, ranging from semen to cerumen. there are, however, practical limi-

tations to the extent to which different biological samples can be used,

and the mechanism of collection and supervision of samples are critical

to the procedure. the drug being tested for, and the period of time

that the clinician wishes to consider, influence the choice of body fluid.

Blood gives the most accurate measurement of drugs currently active

in the system, whereas urine provides a somewhat broader time period

but with less quantitative accuracy. Hair provides a substantially longer

timeframe. Oral fluid testing, though beneficial in terms of procedural

ease, provides information over a short timeframe and in this sense is

less advantageous than urine. Ideally, any positive test result should be

confirmed by a second test working on different physicochemical princi-

ples to the screening test. Accurate interpretation of the drug screening

test within a clinical setting, alongside any other relevant information,

remains the key to the usefulness of any test.

Keywords biological test; blood; drug screening; hair; oral fluid; urine

The variety of different body matrices that can be analysed to determine the presence or absence of different psychoactive sub-stances is extensive, ranging from semen to cerumen (earwax). There are, however, practical limitations to the extent to which biological samples can be used, and the mechanism of collection and supervision of samples are critical to the procedure. This contribution focuses on those biological samples that are com-monly used for testing within various drug treatment settings, namely urine, saliva, blood and hair. Urinalysis is routinely used in hospital-based services, blood in forensic environments, hair analysis for medico-legal cases, and saliva (oral fluid) tests in the prison service and outreach units.

Kim Wolff PhD is Senior Lecturer in the Addictions at the National

Addiction Centre and Head of Graduate Studies for Taught Courses at

the Institute of Psychiatry, King’s College, London, UK. She completed

her PhD at the Research School of Medicine, Leeds University. Her

research interests include methadone pharmacokinetics, pregnancy

and opioid use, biological indicators of drug use and education in the

addictions. Conflicts of interest: none declared.

PsYCHIAtRY 5:12 43

Rationale

Many would advocate that the assessment of psychoactive drug use could reliably be achieved using self-report from the drug user (client). However, there are issues around the method of enquiry – the context, purpose, interviewer characteristics, etc.1 – that may bias self-report. Circumstances in which the user sees the self-report to the enquirer about drug use as influential on his or her own continued treatment or possible loss of privileges are particular examples.

Selecting the biological matrix

The drug being tested for and the period of time that the clinician wishes to consider influence the choice of body fluid. Blood gives the most accurate measurement of drugs currently active in the system, whereas urine provides a somewhat longer timeframe (Tables 1 and 2), but with less quantitative accuracy. Hair pro-vides a substantially longer timeframe.2

Approximate duration of detectability in urine of commonly used substances and some of their metabolites

Substance Duration of detectability

Amphetamine 2–3 days

Benzodiazepines:

  short-acting (triazolam) 1 day

  intermediate (temazepam) 2–4 days

  long-acting (diazepam/nitrazepam) 7 days or more

Cannabinoids (marijuana):

  single use 1–2 days

  moderate use (daily use) 10 days

  chronic heavy use 36 days

Cocaine 6–8 hours

  metabolite/benzoylecgonine 2–3 days

LsD 1 day

nicotine 12 hours

  metabolite/cotinine 2–3 days

Opiates:

  6-monoacetylmorphine 2–4 hours

  morphine/codeine 1 day

  dihydrocodeine 1 day

  morphine glucuronides 2 days

  codeine glucuronides 3 days

Opioids:

  methadone (maintenance dosing) 7–9 days

  buprenorphine 2–3 days

  buprenorphine metabolites 7 days

  propoxyphene 0.5–2 days

source: Wolff et al., 1999.2

Table 1

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Assessment

Detection of psychoactive substances in different body matrices

Drug Blood Urine Hair Oral fluid

Heroin ✓ ✗ ✗ ??+,#

6-mAm ✓ ✓ ✓ ✓morphine ✓ ✓ ✓ ✓Codeine ✓ ✓ ✓ ✓methadone ✓ ✓ ✓ ✓Buprenorphine ✓ ??+ ✓ ??*

Cocaine ✓ ✓ ✓# ✓#

Amphetamine ✓ ✓ ✓ ✓Cannabis ✓ ✓ ??# ✗mDmA ✓ ✓ ✓ ??

LsD ✓ ??+ ?? ??*

✓, substance detectable; ✗, substance not detected; ??, substance not routinely detected.

+, concentration of drug too low.*, not available analytically.#, contamination environment/buccal cavity a problem.

Table 2

Standard drug-testing strategy

The routine drug-testing strategy most widely used is to send urine samples to a laboratory for an initial screen to detect psychoactive drugs of interest. Analysis is performed using a semi-automated commercially available immunoassay or thin-layer chromatography (Toxilab) tests. There are several types of immu-noassay, including: • radioimmunoassay (RIA) • enzyme-mediated immunoassay test (EMIT) • fluorescence polarization immunoassay (FPIA). Recently, several rapid detection devices for drugs of abuse screening have been marketed in the UK. Such tests offer a more rapid turnaround of results to aid clinical decision-making.3 However, all initial drug screen tests are non-specific and iden-tify only in a non-quantitative fashion the class of drug present, such as opioid, amphetamine or benzodiazepine.

Ideally, any positive test result should then be confirmed by a second test working on different physicochemical principles from the screening test. Gas and liquid chromatography with mass spectrometric detection are regarded as the ‘gold standard’ and are favoured when legally defensible results are required. It can-not be overemphasized that the confirmation of screening results is essential.

For amphetamine-specific immunoassays, the confirmation test provides the opportunity to differentiate legitimate medi-cines. For example, pseudoephedrine and phentermine give a positive test result (cross-react) with tests for illicit drugs such as amphetamine and 3,4-ethylenedioxymethamphetamine (MDMA, ecstasy).

For opiate drugs, initial immunoassay tests for mor-phine cross-react with codeine, dihydrocodeine, pholcodeine, 6-monoacetylmorphine (6-MAM), morphine-3-glucuronide and morphine-6-glucoronide. Consequently, if more than one of these substances is present in a urine sample, the test result will

PsYCHIAtRY 5:12 44

relate to the concentration of the sum of all these opiates and their metabolites. Thus an inaccurate picture of the window of detection of opiate drugs in urine may be obtained. The clini-cal benefit of the confirmation test is that it is able to verify the specific substance(s) present. For example, a confirmation test can detect the presence of 6-MAM, the only specific indicator of heroin use.

Applications in the clinical setting

Urine testing is the most reliable and interpretable process avail-able to the clinician and is the technique universally supported by the majority of drug treatment clinics across the UK. Urine testing is recommended as essential to confirm opioid dependence before commencing substitute prescribing with methadone or buprenor-phine.4 Random urine tests are also used to monitor illicit drug use during treatment.

Hair testing is more common in occupational health settings and for medico-legal cases where a longer history of drug use is required. Providing the client’s hair is of sufficient length (hair grows at a rate of 1 cm per month) and thickness (50–100 strands are needed), a drug history covering a 3-month period can be obtained. Cannabis use, however, is very difficult to detect in hair and different rates of drug deposit in the hair strand have been identified for different races, for treated (e.g. bleached) hair and in blond compared with dark-haired people.

Oral fluid (saliva) testing: oral fluid has gained increasing inter-est as a matrix for drugs of abuse testing. An important advantage to the collection of oral fluid (of which, saliva is a key constitu-ent) is that it is relatively easy to obtain, can be carried out by untrained personnel and is less susceptible to adulteration.5,6 The acceptance of oral fluid as a non-invasive, simple biological tool for drug detection has led to the extensive use of this tool in a

0 © 2006 Published by elsevier Ltd.

Assessment

wide variety of clinical settings, although its validity is not well established. Oral fluid testing provides information relating to recent use and is not an ideal alternative to urine.

Blood provides an accurate picture of the immediate situation and is best suited for therapeutic drug monitoring, which has been reported for methadone treatment.

Authenticity

Sample integrity has frequently been an issue with urinalysis and every effort should be made to avoid substitution or adulteration of specimens. Simple observational checks of foaming, colour and temperature are valuable. Collection cups with temperature indi-cator strips are available for immediate monitoring of specimen temperature. For workplace and pre-employment testing, med-ico-legal work and sport testing, chain-of-custody procedures, tamper-free collection vessels and documentation to accompany each sample are required.7

Dilution is a commonly reported problem. The United Kingdom National External Quality Assessment Scheme (UKNEQAS) for drugs of abuse screening in urine reported that 86% of samples found adulterated had been diluted.8 As it is possible to drink large volumes of water and lower urine drug concentrations below the positive cut-off, thresholds for tests of urine creatinine and specific gravity have been proposed. There are also products such as the Instant-View™ Urine ID-Adulteration test device to determine whether urine specimens have been diluted, and URO-GUARD® for assessing the integrity of urine samples, available on the market.

Near-patient drug-testing devices

Urine testing: there has been a huge growth in the development of near-patient test (NPT) kits. These are predominantly for urine sample collection and have the advantage of offering rapid results. Such tests include: • Frontline® (Boehringer Mannheim) • MultiDrug Screen Card IV (Omega Diagnostics Ltd, Ireland) • Syva® Rapid Test d.a.u.® 4 (Dade Behring, USA) • EZ-Screen® (Editek) – for cannabis and cocaine • Triage® (Biosite Diagnostics, USA) – for benzodiazepines,

methadone and cocaine • Abuscreen OnTrak® (Roche Diagnostics) – for cannabis and

morphine • OnTrak TesTcup® (Roche Diagnostics) – for opiates. Serious limitations have been reported for these immunoassay test devices. For cannabinoids, the accuracy varies from 52–90%; for opiates 37–90%; for amphetamines 44–83%; and for cocaine 72–92%.9 Another reported failing of the NPT kits has been the lack of available information about cross-reactivity,3 which is important in drug treatment services, where multiple (poly-)substance use is commonplace. Urine samples for use with NPT kits also have the same issues with authenticity as those collected for laboratory-based testing. In addition, concerns have been raised that without

PsYCHIAtRY 5:12 441

onsite staff training the number of false-positive and false-negative test results could be unacceptably high.10 Confirmation of the test result with all initial tests is recommended as good practice.

Oral fluid testing: recently, oral fluid immunoassay test kits have also become available (e.g. Cozart RapiScan®), offering a less invasive testing procedure. Oral fluid screening is, how-ever, subject to contamination of the buccal cavity from drugs taken intranasally or sublingually, such as cannabis, heroin and buprenorphine respectively. Additionally, the pH of saliva (the main component of oral fluid) can be changed during the sample collection procedure by chewing (stimulation), which may reduce the diffusion of the drug(s) of interest into the oral fluid sample. This could result in false-negative test results.7 Cost is also prohibitive, and there is currently little evidence-based information about these products.11

Accurate interpretation of the drug-screening test within a clinical setting, alongside other relevant information, remains the key to the usefulness of any test. ◆

RefeReNceS

1 Harrell A. Validation of self-report: the research record. In: Rouse BA,

Kozel nJ, Richards LG, eds. self-report methods of estimating drug

use: meeting current challenges to validity. nIDA Research monograph

57. Rockville, mD: national Institute on Drug Abuse, 1985.

2 Wolff K, Farrell m, marsden J, et al. A review of biological indicators

of illicit drug misuse, practical considerations and clinical

usefulness. Addiction 1999; 94: 1279–98.

3 George s, Braithwaite RA. A preliminary evaluation of five rapid

detection kits for on-site drugs of abuse screening. Addiction 1995;

90: 227–32.

4 Department of Health. Drug misuse and dependence: guidelines on

clinical management. London: stationery Office, 1999.

5 Gorodischer R, Burtin P, Hwang P. Levine m, Koren G. saliva versus

blood sampling for therapeutic drug monitoring in children: patient

and parental preferences and an economic analysis. Ther Drug

Monit 1994; 16: 437–43.

6 Allen KR, Azad R, Field HP, Blake DK. Replacement of immunoassay

by LC tandem mass spectrometry for the routine measurement of

drugs of abuse in oral fluid. Ann Clin Biochem 2005; 42: 277–84.

7 Wolff K, Welch s, strang J. specific laboratory investigations for

assessment and management of drug problems. Adv Psychiatr Treat

1999; 5: 180–91.

8 Wilson JF, smith BL. evaluation of detection techniques and

laboratory proficiency in testing for drugs of abuse in urine:

an external quality assessment scheme using clinically realistic

samples. Ann Clin Biochem 1999; 36: 592–600.

9 Jenkins AJ, Goldberger BA. On-site drug testing. totowa, nJ:

Humana Press, 2002.

10 Byrne AG, Pierce A. evaluation of six point of care tests for drugs of

abuse in urine. Bull Internat Assoc For Toxicol 2003; 33: 71–5.

11 De Giovanni n, Fucci n, Chiarotti m, scarlata s. Cozart Rapiscan

system: our experience with saliva tests. J Chromatogr B Analyt

Technol Biomed Life Sci 2002; 773: 1–6.

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