Hair drug testing results and self-reported drug use among primary care patients with moderate-risk illicit drug use

BackgroundThis study sought to examine the utility of hair testing as a research measure of drug use among individuals with moderate-risk drug use based on the internationally validated Alcohol, Smoking, and Substance Involvement Screening Test (ASSIST).MethodsThis study is a secondary analysis using baseline data from a randomized trial of brief intervention for drug misuse, in which 360 adults with moderate-risk drug use were recruited from two community clinics in New Mexico, USA. The current study compared self-reported drug use on the ASSIST with laboratory analysis of hair samples using a standard commercially available 5-panel test with assay screening and gas chromatography/mass spectrometry (GC/MS) confirmation. Both self-report and hair testing covered a 3-month period.ResultsOverall concordance between hair testing and self-report was 57.5% (marijuana), 86.5% (cocaine), 85.8% (amphetamines), and 74.3% (opioids). Specificity of hair testing at standard laboratory cut-offs exceeded 90% for all drugs, but sensitivity of hair testing relative to self-report was low, identifying only 52.3% (127/243) of self-disclosed marijuana users, 65.2% (30/46) of cocaine users, 24.2% (8/33) of amphetamine users, and 2.9% (2/68) of opioid users. Among participants who disclosed using marijuana or cocaine in the past 3 months, participants with a negative hair test tended to report lower-frequency use of those drugs (p < .001 for marijuana and cocaine).ConclusionsHair testing can be useful in studies with moderate-risk drug users, but the potential for under-identification of low-frequency use suggests that researchers should consider employing low detection cut-offs and using hair testing in conjunction with self-report.