AEGiS-13IAC: Increasing HIV incidence among MSM repeat testers in Ontario, Canada, 1992-1998.

13th International AIDS Conference

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

Increasing HIV incidence among MSM repeat testers in Ontario, Canada, 1992-1998.

Int Conf AIDS 2000 Jul 9-14; 13:(abstract no. ThOrC718)

Calzavara L, Burchell A, Major C, Remis R, Corey P, Myers T, Wallace E, Millson M; L. Calzavara, McMurrich Building, 3rd Floor, 12 Queen's Park Crescent West, Toronto, ON M5S 1A8, Canada, Tel.: +(416) 978-4643, Fax: +(416) 971-2704, E-mail: liviana.calzavara@utoronto.ca

OBJECTIVE: To estimate incidence density by risk category among repeat testers in Ontario's diagnostic HIV-testing database.

METHODS: Persons who underwent voluntary, diagnostic HIV testing 2+ times in the period between 1992-98 (data unavailable before 1992) were identified using computerized and manual linkage based on the tester's identifier, birth date, and prior test information. 597 seroconverters and 224,176 repeat negative testers contributed 487,012 person years (PY) of observation. Median inter-test intervals were 1.6 years for seroconverters and 1.8 years for negatives. Risk factor information was provided for 79% of seroconverters and 57% of negatives. The numerator for incidence density was apportioned over time as per Kitayaporn (AIDS 1994, 8: 1443-1450). 95% confidence intervals (CI) were calculated. Poisson regression was used to evaluate differences in incidence.

RESULTS: Among men who have sex with men (MSM), a downward trend in incidence between 1992-1996 was observed, from 1.9 per 100PY in 1992 (CI 1.3-2.5) to 1.0 per 100PY in 1996 (CI 0.7-1.3) (RR = 0.87 per annum, p = 0.006). Incidence subsequently increased to 1.5 per 100PY in 1998 (CI 0.8-2.2) (RR = 1.35 per annum, p = 0.02). No difference was observed between MSM in their 20s and 30s. For injection drug users (IDU), incidence decreased from 0.60 per 100PY in 1992 (CI 0.19-1.0) to 0.29 per 100PY (CI 0.0-0.59) in 1998 (RR = 0.87 per annum, p = 0.04). Gender differences among IDU were not statistically significant. Among heterosexuals, incidence remained constant and was 0.037 per 100PY (CI 0.00-0.076) in 1998.

CONCLUSIONS: Diagnostic HIV-testing databases are a useful, inexpensive data source for monitoring incident HIV infection among those seeking HIV testing. Our analysis suggests an increase in the rate of new infections among MSM since 1996, possibly related to the new, more effective antiretroviral therapies or safer-sex fatigue. These possibilities are being investigated by the Polaris Study.

Keywords: AEGIS, HIV Infections, Canada, Incidence, HIV Seropositivity, Ontario, Acquired Immunodeficiency Syndrome, Risk Factors, Heterosexuality, Safe Sex, Human, Male, epidemiology
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ThOrC718