The reliability and validity of drug users' self reports of amphetamine use among primarily heroin and cocaine users

Relatively few studies have addressed the psychometric properties of self-report measures of amphetamine use. This study examines the reliability and validity of the Risk Behavior Assessment's (RBA) lifetime and recent amphetamine-use questions. To evaluate validity. 4027 out-of-treatment primarily cocaine and heroin users provided urine samples that were compared to self-report data; to evaluate reliability, 218 completed the RBA at two time points, 48 h apart. In the overall sample, self-reports demonstrated moderately high validity, with a 95% accuracy rate (kappa=.54). When analysis was restricted to recent amphetamine users validity was slightly lower (71.5% accuracy; kappa=.41). Test-retest data indicated good reliability for self-reports of ever having used amphetamine (kappa=.79), and amphetamine use in the past 30 days (.75 < r < .91). Out-of-treatment drug users provided accurate self-reports of amphetamine use. Reliable and valid measures are essential for describing and predicting trends in amphetamine use, evaluating the effectiveness of interventions, and developing policies and programs. (C) 2009 Elsevier Ltd. All rights reserved.