A CLUSTER-ANALYSIS OF NOT-IN-TREATMENT DRUG-USERS AT RISK FOR HIV-INFECTION

The purpose of the analysis described here was to classify not-in-trea tment drug users participating in the National Institute on Drug Abuse (NIDA)-sponsored Cooperative Agreement study into several ''homogeneo us'' HIV risk groups using cluster analysis. Data for this analysis (N = 17,778) were collected at 19 study sites in the United States and P uerto Rico. Measures selected for the cluster analysis were limited to (a) current drug use and HIV risk behaviors, (b) mutually exclusive b ehaviors, (c) behaviors directly related to HIV risk, and (d) behavior s that were not statistically rare. Eight homogeneous HIV risk cluster s were produced. Crack cocaine use was the most distinguishing feature of three clusters. Another three clusters were distinguishable by dru g injection and needle use practices. Two additional clusters could no t be grouped with either the crack-or the injection-dominant clusters. Prostitution was the most distinguishing risk behavior of one of thes e clusters, and extremely high drug injection frequencies and relative rates of risky needle use characterized the other. Composition of the clusters varied significantly by gender, race/ethnicity, educational attainment, and drug use characteristics. In addition, perceptions and behaviors initiated to reduce the chances of becoming infected with H IV varied by cluster. Subjects in the crack-predominant clusters repor ted low perceptions of the chances of getting AIDS. Perceptions of the chances of becoming infected with HIV among subjects in the injection -predominant clusters were strongly related to injection frequency. Se roprevalence was also related to cluster. Higher rates of HIV infectio n were evident among the injection-predominant clusters, and higher ra tes were related to frequency of injection and the rate of risky needl e use. Among the crack-predominant clusters, the relationship between drug use and sexual behaviors and HIV infection was less clear.