Recorded presentation

Gary Goldbaum, MD, MPH, Senior Medical Epidemiologist, Public Health-Seattle & King County, 400 Yesler Way, 3rd Floor, Seattle, WA 98104, 206-296-4991, gary.goldbaum@metrokc.gov, William J. Reidy, MHA, MPH, Department of Epidemiology, University of Washington, Box 357236, Seattle, WA 98195, and Susan Buskin, PhD, MPH, Public Health - Seattle & King County, 400 Yesler Way, 3rd floor, Seattle, WA 98104.

Background: Although crucial to public health planning efforts, HIV incidence has been difficult to measure directly. The Serologic Testing Algorithm for Recent HIV Seroconversion (STARHS) uses a modified (less-sensitive) HIV enzyme-linked immunosorbant assay (LS-EIA) to identify recently infected persons, permitting incidence estimates based on cross-sectional (rather than cohort) testing. We applied STARHS to sera from persons tested at publicly-funded testing sites in King County, Washington. Methods: The conventional Abbott and Vironostika HIV-1 EIA tests were modified per CDC protocol (increasing dilutions and reducing incubation times). After obtaining human subjects approval, we applied STARHS to 439 stored and 458 prospectively obtained HIV-positive sera representing 897 persons. Incidence was estimated as I = (n/N)(1/ω)(365 days/1 year) where n = the number testing LS-EIA non-reactive, N = number of susceptibles (HIV- plus LS-EIA non-reactive, ω= the window period (mean time between seroconversion on the EIA and LS-EIA, estimated as 129 [Abbott test] or 170 [Vironostika test]). Results: For all persons tested at these sites from January, 1997, through September, 2003, the STARHS incidence was 0.7 per 100 person-years (95% confidence limits [CL] 0.6, 0.9). HIV incidence was highest for men who have sex with men (MSM) and who inject drugs (4.3 per 100 person-years, 95% CL 2.2, 6.3) and MSM who do not inject drugs (2.5 per 100 person-years, 95% CL 2.1, 2.9). No consistent trend in incidence over time was observed for any risk population. Conclusions: In King County, MSM have sustained the highest incidence of HIV infection.

Learning Objectives: After this session, participants will be able to

• Describe how modified HIV testing technology can be used to estimate HIV incidence;
• Describe limitations in such approaches; and
• Describe direct estimates of HIV incidence in a major U.S. metropolitan area.

Keywords: HIV/AIDS, Epidemiology

Presenting author's disclosure statement:
I do not have any significant financial interest/arrangement or affiliation with any organization/institution whose products or services are being discussed in this session.

Recorded presentation