Reliability of homeless women's reports - Concordance between hair assay and self report of cocaine use

Background: To assess the concordance of homeless women's self-reported dru g use with objective data. Objective: To determine whether objective data (e.g., hair assays) are nece ssary supplements to self reports in assessing homeless women's cocaine use . Method: Self reports of cocaine use by 1,037 homeless women were compared t o objective data based on radioimmunoassay of hair; independent correlates of cocaine use and underreporting were assessed using logistic regression. Results: Forty-two percent of the women self-reported cocaine use in the pa st 6 months, whereas 49% had positive hair assays. Over 25% underreported c ocaine use; however, underreporting decreased as hair cocaine levels increa sed. Predictors of underreporting included being Latino, younger and living primarily in shelters. Nevertheless, independent predictors of self-report ed cocaine use and positive hair assays were identical. Conclusion: Homeless women's self-reports of cocaine use are fairly accurat e. Objective data are particularly critical for assessing cocaine use among subgroups who are fearful of sanctions or use cocaine relatively infrequen tly or in smaller amounts.