Trends in HIV incidence in Ontario based on the detuned assay: Update to October 2000

1. Trends in HIV incidence in Ontario based on the detuned assay: Update to October 2000 Robert S. Remis, Carol Major, Carol Swantee, Margaret Fearon, Evelyn Wallace, Elaine Whittingham Department of Public Health Sciences, University of Toronto HIV Laboratory, Laboratory Services, Ontario Ministry of Health and Long-Term Care Public Health Branch, Ontario Ministry of Health and Long-Term Care Canadian Association of HIV/AIDS Research10th Annual Scientific ConferenceToronto, Ontario, May 31-June 3, 2001

2. Acknowledgements • At the HIV Laboratory • Lisa Santangelo and Cindi Farina, data collection • Lynda Healey, detuned assay • Elaine McFarlane, data entry screens • Len Neglia, mailout of questionnaires • Regional PHLs, mailout of questionnaires • Physicians who prescribe HIV testing, supplementary data • Ontario HIV Treatment Network, funding

3. Introduction • Serodiagnostic data may useful for surveillance • However, • persons who test may not be representative • data quality inconsistent • True HIV incidence and HIV prevalence cannot be derived directly from data

4. Introduction • Testing of HIV-positive specimens using less sensitive (“detuned”) assay permits the identification of persons who recently seroconverted (< 4 months) • Allows calculation of HIV incidence density, an important indicator usually difficult to measure

5. Study objectives • To accurately determine the number of persons newly testing positive for HIV • To determine the distribution of exposure category among newly diagnosed HIV-infected persons • To estimate HIV incidence density among persons undergoing HIV testing

6. Data collection and management • Questionnaire sent with HIV-positive results and 1:200 sample of HIV-negative results • Data on risk factors for HIV infection and HIV test history • Questionnaire may be returned • by mail or fax • by telephone interview • Data entered in Microsoft Access

7. Laboratory methods • Abbott 3A11 EIA kit modified as follows: • serum diluted to 1:20,000 • incubation period reduced to 30 minutes • cut-off value increased

8. Study questionnaires mailed and returned, Oct 1999 to Dec 2000

9. Exposure category classification according to HIV test requisition, returned questionnaires and modeled distribution, HIV-positives

10. HIV-negatives

11. Previous testing history among "first-time" positive diagnoses

12. HIV incidence (per 100 person-years) for selected exposure categories by health region

13. HIV incidence for selected exposure categories by health region

14. HIV incidence (per 100 person-years) among IDU, by health region and sex

15. HIV incidence (per 100 person-years) among HR heterosexuals, by health region and sex

16. HIV incidence by quarter, MSM

17. HIV incidence by quarter, MSM-IDU

18. HIV incidence by quarter, IDU

19. HIV incidence by age group, selected exposure categories

20. Summary of findings • Exposure category distribution among those with risk factor data not representative • ~9% of persons with an apparent first HIV-positive test were previously tested in Ontario • Trends in HIV incidence • MSM: highest in Toronto but decreasing; low and stable in Ottawa; intermediate elsewhere but increasing • IDU: high in Ottawa; lower elsewhere • Incidence apparently not higher in younger persons

21. Interpretation • Number of discordant samples and HIV tests by exposure category modeled • Interpretation of HIV incidence must incorporate knowledge of patterns in HIV test seeking behaviours • Observed HIV incidence likely higher than for population

22. Conclusions • HIV serodiagnostic program extremely useful for HIV surveillance • Due to important problems in missing and unrepresentative data on risk factors and HIV test history, available data must be enhanced through supplementary means on an ongoing basis • Detuned assay provides a critical indicator of trends in the epidemic at low cost