Detection of Illicit Substance Use Among Persons With Schizophrenia by Radioimmunoassay of Hair

OBJECTIVE: Illicit substance use is a potent risk factor for poor outcomes in schizophrenia, yet methods for detecting substance use consistently underestimate the problem. The purpose of this study was to assess whether use of a relatively new method of detection, radioimmunoassay of hair, improved detection and was acceptable to patients with serious mental illness. METHODS: Persons already participating in a longitudinal naturalistic study of schizophrenia treatment were approached for participation in this study. The 203 persons who consented were interviewed and submitted urine and hair samples for laboratory measures of potential substances of abuse. Radioimmunoassay of hair was used to detect the use of amphetamines, cocaine, marijuana, opiates, and phencyclidine (PCP) in the preceding three months. RESULTS: Of the 203 participants, only 33 (16.3 percent) self-reported illicit substance use, and only 25 (12.4 percent) had a positive urine test, but 63 (31.0 percent) had a positive hair assay. When all detection methods were combined—self-report, urine test, and hair assay—78 participants (38.4 percent) were classified as users in the preceding three months. Few of those asked to participate (20, or 9.9 percent) refused hair analysis. CONCLUSIONS: Radioimmunoassay of hair appears to be a promising method for improving assessment of illicit substance use among persons with schizophrenia. Most participants appeared to find hair analysis an acceptable procedure, although this conclusion warrants further study. The test's three-month window of detection may make it a valuable method for assessing and monitoring use over time.