标题：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
摘要：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. Measuring trends in HIV epidemics is critical for assessing the community-level effectiveness of HIV prevention programs and risk reduction and for eventually establishing control over HIV epidemics. Collecting valid HIV incidence data over time, however, is often quite difficult. Cohort studies, in which uninfected individuals are studied over time to observe the rate of new infections, are typically very expensive and logistically complex. The recently developed Serologic Testing Algorithm for Recent HIV Seroconversion (STARHS) system 1 – 3 provides a means for identifying likely incident HIV infections in cross-sectional HIV seroprevalence surveys. In this system (also known as the “sensitive/less sensitive” or “detuned” assay), 2 enzyme immunoassays (EIAs) are used to test each sample. One EIA is the standard highly sensitive test used to diagnose HIV infection; the other has been deliberately “detuned” to be less sensitive to antibody levels characteristic of early infection. Samples that test positive on both the diagnostic assay and the detuned assay are considered to have high levels of HIV antibody (both antibody titers and affinity) and to represent relatively long-term prevalent HIV infections. Samples that test positive on the diagnostic assay but negative on the less sensitive assay are considered to have lower antibody levels and to represent recent infections. Multiple technical issues have delayed the widespread use of STARHS, but the few studies published to date suggest that the method may have substantial practical advantages over cohort studies as a method for estimating HIV incidence. 4 , 5 We report data from STARHS testing on injection drug users (IDUs) entering the Beth Israel Medical Center drug abuse detoxification program in New York City from 1990 to 2002. This time period includes a “natural experiment” of substantial expansion of HIV prevention services for IDUs in New York City. We believe that this is the first use of STARHS to assess a large-scale expansion in HIV prevention for IDUs. HIV was introduced into the IDU population in New York City in the middle 1970s and spread rapidly during the late 1970s and early 1980s. 6 HIV prevalence then stabilized at approximately 50% from the early 1980s to the early 1990s. 7 In the second half of 1992, syringe exchange programs received legal authorization, and funding from New York State subsequently underwent rapid expansion. The estimated numbers of syringes exchanged by the programs in New York City increased from approximately 250 000 in 1991 to 1 300 000 in 1994, to 2 400 000 in 1996, and stabilized at 3 000 000 in 2000 and 2002. 8 In addition to exchanging needles and syringes, the programs provided free condoms, voluntary HIV counseling and testing, referrals to treatment for HIV infection, “prevention for positives” programs, and referrals to drug abuse treatment, among other services. This legalization, funding, and expansion of syringe exchange was undertaken with a clear expectation by public health authorities that it would be followed by a reduction in HIV transmission among IDUs in the city. 9 The STAHRS testing reported here provides a direct assessment of whether that expectation was met.
