HIV incidence among injection drug users in New York City, 1990 to 2002: Use of serologic test algorithm to assess expansion of HIV prevention services

Objectives. We sought to estimate HIV incidence among injection drug users (IDUs) in New York City from 1990 to 2002 to assess the impact of an expansion of syringe exchange services. Syringe exchange increased greatly during this period, from 250000 to 3000000 syringes exchanged annually. Methods. Serum samples were obtained from serial cross-sectional surveys of 3651 IDUs. HIV-positive samples were tested with the Serologic Test Algorithm for Recent HIV Seroconversion (STARHS) assay to identify recent HIV infections and to estimate HIV incidence. Consistency with other incidence studies was used to assess strengths and limitations of STARHS. Results. HIV incidence declined from 3.55/100 person-years at risk (PYAR) from 1990-1992, to 2.63/100 PYAR from 1993-1995, to 1.05/100 PYAR from 1996-1998, and to 0.77/100 PYAR from 1999-2002 (P <.001). There was a very strong negative linear relationship (r=-.99, P <.005) between the annual numbers of syringes exchanged and estimated HIV incidence. These results were highly consistent with a large number of shorter incidence studies among IDUs conducted during the time period. Conclusions. STARHS testing of samples from large serial cross-sectional surveys can provide important data for the assessment of community-level HIV prevention.