Application of the BED capture enzyme immunoassay for HIV incidence estimation among female sex workers in Kaiyuan City, China, 2006–2007

SummaryObjectiveTo estimate HIV incidence among female sex workers (FSWs) by serial cross-sectional surveys and IgG-capture BED-enzyme immunoassay (BED-CEIA).MethodsWe conducted three cross-sectional surveys, 6 months apart, among all consenting FSWs in Kaiyuan City, China. HIV antibody-positive samples were also tested by BED-CEIA.ResultsAmong 1412 unique participants, 475 tested HIV-negative and attended >1 survey (longitudinal cohort). Compared to 786 HIV-negative FSWs who only participated once, the longitudinal cohort reported more illicit drug use (10.9% vs. 7.4%, p = 0.03), injected drugs more often in the previous 3 months (8.8% vs. 5.3%, p = 0.02), and had more positive urine opiate tests (13.7% vs. 8.9%, p = 0.008). Four participants in the longitudinal cohort seroconverted over the year, with an overall incidence of 1.1/100 person-years (95% confidence interval (CI) 0.3–2.8). Crude BED-CEIA incidence was 3.4/100 person-years (95% CI 2.3–4.4) with adjusted rates similar to the cohort incidence: McDougal, 1.5/100 person-years (95% CI 1.0–2.0); Hargrove, 1.6/100 person-years (95% CI 1.1–2.1). The BED-CEIA false-positive rate was 4.4% (10/229) among samples from FSWs known to be infected ≥365 days.ConclusionsAlthough limited by power, this study provides additional data towards validating BED-CEIA in China. If confirmed by other studies, BED-CEIA will be a useful tool to estimate HIV incidence rates and trends.