Latent classes of injection risk behavior in a cohort of young injection drug users

Latent class analysis was used to identify classes of injection risk behavior in a sample of young injection drug users (IDUs) enrolled in the Collaborative Injection Drug Users Study III, and eligible for participation in the Drug Users Intervention Trial (DUIT). The risk behaviors included were frequency of sharing the following: 1) syringes, 2) cookers, 3) cottons, and 4) rinse water; 5) number of syringe-sharing partners; 6) frequency of using a new sterile syringe when dividing drugs in a syringe; and 7) frequency of cleaning needles with bleach when using a shared syringe. Four risk classes were identified: 1) overall low risk (33%), 2) equipment sharing only (22%), 3) moderate risk characterized by low-frequency sharing of syringes (19%), and 4) overall high risk (27%). Subjects were assigned to their most likely class, and multinomial logistic regressions were performed for each covariate. Women and younger IDUs were more likely to belong to the high-risk class; Black and Hispanic IDUs were more likely than White IDUs to belong to the low-risk class. The high-risk class had higher rates of homelessness, income from illicit activities, alcohol use, and non-injection drug use. The low-risk class was distinguished by fewer injection partners, and the low-risk and equipment-only classes had lower frequencies of injection compared to the moderate and high-risk classes. The risk classes had similar levels of HIV/HCV transmission knowledge, but differed significantly on peer norms for syringe sharing and self-efficacy for safer injection. Participation in the intervention trial did not vary by class membership.