Drug injection rates and needle-exchange use in New York City, 1991-1996.
Objectives included (1) to develop methods for identifying injection drug users with accelerating injection habits so they might be referred to counseling and treatment and (2) to investigate behavioral correlates of accelerating injection habits, including syringe-exchange program utilization. Data on drug use, enrollment in methadone maintenance, and demographic variables were obtained from 328 subjects who were seronegative for human immunodeficiency virus (HIV) who attended anywhere from 4 to 11 quarterly study visits for interview, HIV pretest counseling and risk reduction counseling, and blood donation for HIV antibody testing. Subjects were recalled 2 weeks after each study visit to receive their results and post-test counseling. We characterized subjects according to their patterns of drug injection as accelerating, decelerating, or stable, using intraindividual regression analyses and categorization rules, and by syringe-exchange use as consistent users, sporadic users, or nonusers. The present subjects included 52% with decelerating, 29% with stable, and 19% with accelerating rates of drug injection. There were 128 subjects (39%) who were categorized as consistent users of syringe-exchange programs, 84 (25%) were categorized as sporadic users, and 116 (35%) were categorized as nonusers. All syringe-exchange groups showed significantly decelerating drug injection. Rates of decline were significantly less, however, among consistent syringe-exchange users than sporadic or nonusers of syringe exchanges. Categorical analysis also showed significant differences among groups, with 30% of consistent syringe-exchange program users having accelerating rates of drug injection compared to 9% of nonusers and 17% of sporadic users. That consistent syringe-exchange users included a larger proportion of individuals whose drug habits were accelerating than did sporadic users or nonusers of syringe exchanges suggests a need for improved identification and counseling of such subjects by syringe-exchange program staff. The present statistical approaches may be of value in targeting such efforts. The ability of a syringe-exchange program to attract a disproportionate share of drug users with accelerating rates of drug injection underscores the importance of these programs to HIV prevention efforts.