AEGiS-13IAC: Use of the sensitive/less sensitive EIA to monitor trends in HIV seroconversion among intravenous drug users at a drug treatment center in San Francisco, 1989-1998.

13th International AIDS Conference

Durban, South Africa - July 9-July 14, 2000

Use of the sensitive/less sensitive EIA to monitor trends in HIV seroconversion among intravenous drug users at a drug treatment center in San Francisco, 1989-1998.

Int Conf AIDS 2000 Jul 9-14; 13:(abstract no. ThOrC666)

Louie B, McFarland W, Kellogg T, Liska S, Miller M, Murrill C
B. Louie, San Francisco Department of Public Health, Public Health Laboratory, 101 Grove St. 4th Fl, San Francisco, CA 94102, United States, Tel.: +1 415 554 2800, E-mail: brian_louie@ph.sf.ca.us

BACKGROUND: Intravenous drug users (IDUs) accessing treatment are used as sentinel populations to monitor the HIV epidemic. Trends in HIV prevalence have been used to identify emerging trends in HIV incidence. However, trends in HIV prevalence do not necessarily reflect trends in HIV incidence. We measured HIV incidence among IDUs in treatment directly by applying the new Sensitive/Less Sensitive EIA.

METHODS: Subjects were clients of a drug treatment clinic in San Francisco providing specimens for syphilis serology at intake for detoxification or methadone treatment and at annual medical exams. HIV testing was conducted on residual sera after specimens and records were stripped of identifying information. To identify recent seroconversions and estimate HIV incidence, HIV+ specimens were retested using a modified EIA (Abbott 3A11 LS) which becomes reactive approximately 0.35 years after positive Western Blot. Annualized incidence was estimated as the number HIV+ yet LS-/(number tested - number LS+) ó Ç Ö 0.35 years.

RESULTS: Of 6,787 tests, 456 (6.7%) were HIV+. Only six HIV+s were recent seroconversions (LS-) (annualized incidence 0.27% per year). The table displays ten-year trends in HIV prevalence and incidence. Outcome 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 HIV prevalence (%) 7.74 6.90 6.51 6.26 7.91 8.08 7.21 5.81 4.38 3.06 HIV incidence (%/yr) 0 0 0.21 na 1.10 1.14 0 0 0 0 Adjusting for age, race, and sex, a borderline decrease in HIV prevalence was noted over the period (p = 0.1). Discussion: Very few clients accessing treatment seroconverted. Low HIV incidence among IDUs in treatment stands in contrast to recent high rates among street- and hospital- recruited IDUs in San Francisco. Epidemiological studies among IDUs not in treatment are needed to identify emerging trends in HIV incidence and to effectively target primary prevention programs.

Keywords: AEGIS, Substance Abuse, Intravenous, HIV Seropositivity, HIV, HIV Infections, Incidence, Substance Abuse Treatment Centers, Prevalence, Equine Infectious Anemia, HIV Seroprevalence, Organothiophosphorus Compounds, HIV Antibodies, Disease Outbreaks, Epidemiologic Studies, San Francisco, methamidophos, Human, Animal, utilization, immunology
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