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HIV incidence among repeat HIV testers at a county hospital,
San Francisco, California, USA.
Journal of Acquired Immune Deficiency
Syndromes 2001;28(1):59-64.
Kellogg TA,
McFarland W, Perlman JL, Weinstock H, Bock S, Katz MH, Gerberding JL, Bangsberg
DR.
Abstract
OBJECTIVES: To estimate HIV incidence, characterize correlates of HIV seroconversion,
and monitor temporal trends in HIV transmission among patients repeatedly
tested for HIV by a county hospital in San Francisco. DESIGN: Retrospective
longitudinal study. METHODS: HIV incidence was retrospectively calculated
among persons voluntarily tested for HIV antibody more than once at San Francisco's
county hospital or one of its affiliated satellite community clinics between
1993 and 1999. Linkage of HIV test results in computerized databases identified "seroconverters" as
individuals who had a negative antibody test followed by a positive test.
The interval between tests was used as the person-time at risk. Cox proportional
hazards analysis identified correlates of HIV seroconversion. RESULTS: A
total of 84 HIV seroconversions were identified among 2893 eligible patients
repeatedly tested for HIV antibody over a cumulative 5860 person-years (PYs)
(incidence of 1.4 per 100 PYs, 95% confidence interval [CI]: 1.2-1.7). The
majority of seroconversions (71 [84.5%]) were among injection drug users
(IDUs) (incidence of 2.0 per 100 PYs, CI: 1.6-2.4). HIV incidence was highest
among men who have sex with men (MSM) who were also IDUs (incidence of 3.8
per 100 PYs, CI: 2.7-5.1) and lowest among non-IDUs, heterosexual men, and
non-IDU women (incidence of 0.3 per 100 PYs, CI: 0.1-0.6). In multivariate
analysis, correlates of HIV seroconversion were age 25 to 29 years (hazard
ratio [HR] = 3.9, CI: 2.4-6.3), MSM (HR = 2.9, CI: 1.9-4.4), and IDU (HR
= 3.2, CI: 1.8-5.8). Overall, no temporal trend in annual HIV incidence was
noted during the study period; however, HIV incidence among MSM IDUs increased
from 2.9 per 100 PYs in 1996 to 4.7 per 100 PYs in 1998. CONCLUSIONS: The
rate of seroconversion in this hospital and affiliated clinic population
is unexpectedly high. Moreover, HIV transmission among IDU patients has not
decreased over the last several years. The San Francisco county hospital
provides a high-risk sentinel population to monitor emerging trends in HIV
transmission, especially among IDUs, and presents multiple opportunities
for prevention interventions, because these patients are being seen repeatedly
by clinicians.