Reliability of Homeless Women’s Reports: Concordance Between Hair Assay and Self Report of Cocaine Use

BACKGROUNDTo assess the concordance of homeless women’s self-reported drug use with objective data. OBJECTIVETo determine whether objective data (e.g., hair assays) are necessary supplements to self reports in assessing homeless women’s cocaine use. METHODSelf reports of cocaine use by 1,037 homeless women were compared to objective data based on radioimmunoassay of hair; independent correlates of cocaine use and underreporting were assessed using logistic regression. RESULTSForty-two percent of the women self-reported cocaine use in the past 6 months, whereas 49% had positive hair assays. Over 25% underreported cocaine use; however, underreporting decreased as hair cocaine levels increased. Predictors of underreporting included being Latino, younger and living primarily in shelters. Nevertheless, independent predictors of self-reported cocaine use and positive hair assays were identical. CONCLUSIONHomeless women’s self-reports of cocaine use are fairly accurate. Objective data are particularly critical for assessing cocaine use among subgroups who are fearful of sanctions or use cocaine relatively infrequently or in smaller amounts.