Measuring Substance Use Among Detainees: Self-Report or Bioassay?
Self-report and bioassay are the two techniques most commonly used to detect substance use in detained populations. There is great variety within each of these techniques. Self-report information can be obtained by using a mail questionnaire, a self-administered computerized instrument, or a face-to-face interview. Bioassay, or biological measurement, can be done with various tissues and fluids. No gold standard exists for assessment of substance use. Each method has its strengths and weaknesses.
Self-Report
Self-report is the least expensive, most easily administered method of assessing substance use. For this reason, large national studies rely on self-report data to generate prevalence rates of substance use (Craddock, Collins, and Timrots, 1994; Harrison and Gfroerer, 1992; Golub et al., 2002; U.S. Department of Health and Human Services, 1996). For self-report data to be valid, subjects must understand the questions, accurately recall the information requested, and disclose information honestly (Lessler and O’Reilly, 1997; Turner et al., 1998; Wasserman et al., 2002; Catania et al., 1990; Huang, Watters, and Case, 1988; Miller, 1997). Each of these requirements poses challenges in juvenile justice settings.
Understanding questions. Drugs of abuse have a wide range of street names, and these names vary greatly from setting to setting. Because subjects may be unfamiliar with street names of drugs used in other neighborhoods, social strata, or ethnic groups, interviewers must be trained to be sensitive to each subject’s background, demeanor, and linguistic preferences. In addition, because many juvenile justice detainees have limited reading skills, self-administered questionnaires and computerized instruments that are useful in other settings may be problematic for detained youth.
Recalling information. Drug use itself might compromise a subject’s ability to recall specifics. However, although impaired recall poses problems for assessing patterns and details of substance use, recall of recent use is unlikely to be so impaired as to prevent identification of youth in need of treatment.
Answering honestly. The greatest barrier to accurate self-reporting of drug use is unwillingness to disclose honestly. Detainees—both adult and juvenile—are understandably reticent about reporting illegal behavior, and self-reported drug use data from these groups, therefore, are likely to lack validity.2
Bioassay
At its best, bioassay promises to circumvent the problems of self-reporting. Bioassay, however, does not solve all the problems associated with measuring drug use. Common to any bioassay is the premise that the drug or a metabolic byproduct unique to the body’s processing of the drug will be present in the fluids or tissues tested. Two issues confront all bioassay methods: first, what tissue or fluid to test; and second, how to measure the presence of a drug or its metabolite. These two issues frame most of the debate over the validity and usefulness of bioassay.
Choosing tissues or fluids. Bioassays can be done with urine, hair, saliva, sweat, blood, and semen. Most detention facilities use urine or hair, both of which are relatively easy to collect.3 In general, urine testing is sensitive only to drugs used within the last 2 or 3 days (Mieczkowski and Newel, 1993; Cone, 1997; Council on Scientific Affairs, 1987; Wolff et al., 1999).4 Although hair analysis initially promised to provide a record of drug use for weeks or even months, troublesome issues have yet to be resolved: external contamination may result in false-positive findings,5 and cocaine may bind to hair more readily than cannabis or opiates and may bind more readily to some types of hair than others (which may cause racial differences in sensitivity to hair analysis) (Baumgartner, Hill, and Blahd, 1989; Mieczkowski and Newel, 1997; Miller, Donnelly, and Martz, 1997).
Choosing a method of analysis. Many techniques are available for identifying drugs in urine or hair (Visher and McFadden, 1991; Riley, Lu, and Taylor, 2000):
- Gas chromatography/mass spectrometry. GC/MS is the best method
for detecting drugs (i.e., the least likely to produce false-negative
or false-positive results), but it is also the most costly. GC/MS requires
trained technicians, lengthy preparation of samples, and expensive
laboratory equipment.
- Other chromatographic methods. High-performance liquid chromatography
(HPLC) performs well but also requires expensive equipment. Thin-layer
chromatography (TLC) is inexpensive but not as reliable as other chromatographic
methods.
- Immunoassay. The most commonly used immunoassay methods are radioimmunoassay and enzyme-multiplied immunoassay. In both methods, a drug-binding antibody is added to a sample, and the level of antibody activity is then measured. Although these methods are relatively inexpensive and easily executed, they have drawbacks: a different antibody must be developed for each drug tested, and the antibodies sometimes bind to substances that are chemically similar to the drug in question (resulting in false positives, such as mistaking over-the-counter cold remedies for amphetamines).
Previous Studies
Research has demonstrated not only high levels of substance use among detained youth but also shortcomings of self-report measures in this population. Table 1 summarizes seven studies that used self-reports and/or bioassays to measure drug use in juvenile detainees.
Study |
Design |
Prevalence Based
on Self-Reports |
Prevalence Based
on Urinalysis |
Prevalence Based
on Hair Analysis |
Veracity
of Self-Report Data* |
|---|---|---|---|---|---|
| Wislar and Fendrich, 2000 | N=3,048 juvenile arrestees and detainees | Past 3
days Cannabis 31% Cocaine 2.8% |
Cannabis 31.4% Cocaine 7.3% |
Not administered | Past 3
days Cannabis 60.4% Cocaine 22.7% |
| Dembo et al., 1999 | N=80 youth arrested and completing a court-ordered treatment program | Past 3
months
Cannabis 51.3% Cocaine 7.5% |
Not administered at baseline | Cannabis 32.5% Cocaine 18.75% |
Cannot be computed• |
| Mieczkowski, Newel, and Wraight, 1998 | N=407 juvenile detainees interviewed within 48 hours of detention | Past 3
days Cannabis 25.3% Cocaine 0.9% Past 30 days Cannabis 50.6% Cocaine 3.2% Ever Cannabis 85.6% Cocaine 13.2% |
Cannabis 34.8% Cocaine 7.1% |
Cannabis 38.5% Cocaine 22.0% |
Cannot be computed• |
| Magura, Kang, and Shapiro, 1995 | N=121 youth followed up after release from jail | Past 30
days Cocaine 22% Past 3 months Cocaine 23% Ever Cocaine 35% |
Not administered | Cocaine 51%– 67%‡ |
Past 3
months Cocaine 22.1%– 23.4%‡ |
| Feucht, Stephens, and Walker, 1994 | N=88 detained youth | Past
month Cocaine 3.4% Past 90 days Cocaine 5.7% Ever Cocaine 7.4% |
Cocaine 7.8% | Cocaine 56.8% | Cannot be computed• |
| Dembo et al., 1993 | N=399 detained youth | Authors do not provide self-report data | Cannabis
34.3% Cocaine 9% Opiates 0.5% |
Not administered | Cannot be computed• |
| Dembo et al., 1987 | N=66 juveniles ordered into secure detention (6 refused urine test) | Authors do not provide self- report data | Cannabis
53% Cocaine 6.1% Barbiturates 4.6% |
Not administered | Recent § Cannabis 81% Cocaine 50% Lifetime Cannabis 100% |
* Among youth who tested positive, the percentage who reported use. • Veracity cannot be computed for several studies because self-report data are not provided specifically for positive urinalysis or hair analysis test results. ‡ The ranges reflect the authors’ two cutoff levels for establishing cocaine content in hair: > 2 ng/10 mg and > 5 ng/10 mg. The latter, more conservative figure is the conventional cutoff level. § The authors do not define recency of use. |
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As the table shows, the level of self-reported cannabis and cocaine use varies markedly from study to study. For both drugs, self-reports of use decline sharply when subjects are asked about more recent use. Urinalysis results for cannabis are fairly consistent for three of the four studies; results for cocaine are more consistent across studies. Hair analysis results vary for both drugs. The variation in bioassay results may be attributable to the studies’ methodological differences: they sampled youth at different stages of the juvenile justice process, were designed for different purposes, and had different rates of refusal or noncompliance.
Veracity of self-report data could be computed for only a few of the studies. For cannabis, one study found that 60.4 percent of juveniles who tested positive reported use in the past 3 days, and another found that all juveniles who tested positive reported lifetime use and 81.0 percent reported “recent” use. For cocaine, veracity of self-report data was strikingly poor: of those who tested positive, only 22.7 percent reported use in the past 3 days, 22.1 to 23.4 percent reported use in the past 3 months, and 50.0 percent reported “recent” use. In other words, at least half of recent cocaine users denied use.
Studies of detained adults (Golub et al., 2002; Gray and Wish, 1999; Harrison, 1995; Mieczkowski, 1990) have found self-report veracity levels for cannabis and cocaine that are similar to those found for juveniles. As with juveniles, self-reports of use decline when subjects are asked about more recent use, and veracity levels are markedly lower for cocaine than for cannabis. For adults, the veracity level for opiate use is generally higher than that for cocaine use.
To summarize:
- Both self-report and bioassay data confirm that substantial numbers
of juvenile and adult detainees use drugs.
- Self-report veracity is poor among both juveniles and adults, especially
when they are asked about recent use.
- Self-report veracity is related to the type of drug. Cannabis use is more likely to be reported than cocaine use, probably because the former is more socially acceptable (Golub et al., 2002; Harrison, 1995; Mieczkowski et al., 1991; Fendrich and Xu, 1994) and because it carries less severe legal consequences.
Two key questions have not been adequately addressed in the existing literature: First, does the veracity of self-reported drug use differ across demographic groups (i.e., age, gender, and race/ethnicity)? Second, what is the best approach for identifying drug use among juvenile detainees, given the demonstrated shortcomings of the various measures? These questions are addressed below.
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