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Trends in HIV incidence in Ontario based on the detuned assay: Update to December 2002

Trends in HIV incidence in Ontario based on the detuned assay: Update to December 2002. Robert S. Remis, Carol Major, Carol Swantee, Margaret Fearon, Robert W. H. Palmer, Evelyn Wallace, Elaine Whittingham Department of Public Health Sciences, University of Toronto

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Trends in HIV incidence in Ontario based on the detuned assay: Update to December 2002

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  1. Trends in HIV incidence in Ontario based on the detuned assay: Update to December 2002 Robert S. Remis, Carol Major, Carol Swantee, Margaret Fearon, Robert W. H. Palmer, 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 Ontario HIV Treatment Network 5th Annual Research Day Toronto, Ontario, November 3-4, 2003

  2. Introduction • Serodiagnostic data may be useful for surveillance • Testing of HIV-positive specimens using less sensitive (detuned” or STAHRS) assay permits the identification of persons who recently seroconverted (e.g.<4 months) • Allows the calculation of HIV incidence density, an important indicator usually difficult to measure

  3. Study objectives • To estimate HIV incidence density among persons undergoing HIV testing according to exposure category and region of test • To monitor trends in HIV incidence density among specific populations particularly affected by the HIV epidemic

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

  5. 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 • For specimens tested in October 2001 or later, we used Organon-Teknika Vironostika assay allowing for different “window period” at different cut-off (70-336 days)

  6. Questionnaires Kaplan - Meier returned by Mailed Returned Proportion 4 mon. 8 mon. HIV-positive HIV-negative Total 3,161 3,419 6,580 69% 71% 70% 73% 73% 78% 78% Study questionnaires mailed and returned, October 1999 to December 2002 2,187 2,440 4,627

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

  8. Toronto Ottawa Rest of Ontario Overall Incidence Tested Incidence Tested Incidence Tested Incidence MSM MSM-IDU IDU HR hetero LR hetero 2.8 6.9 0.25 0.16 0.02 5,157 82 3,883 3,843 70,830 1.8 16.23 0.70 0.09 0.02 11,910 1,311 28,299 22,465 318,548 0.96 0.31 0.15 0.06 0.01 39,603 1,763 46,034 40,674 646,721 2.1 2.4 0.23 0.10 0.01 HIV incidence (per 100 person-years) for selected exposure categories by health region Tested 22,535 370 13,853 14,366 257,343

  9. MSM: HIV incidence by six-monthperiod and region,Ontario, October1999-December 10th 2002

  10. IDU: HIV incidence by six-month period and region,Ontario,October1999- December 10th 2002

  11. High risk heterosexuals: HIV incidence by six-month period and region, Ontario,October1999-December 10th 2002

  12. Low risk heterosexuals: HIV incidence by six-month period and region, Ontario, October1999-December 10th 2002

  13. Summary of findings • Exposure category distribution among those with risk factor data not representative • Trends in HIV incidence • MSM: highest in Toronto but decreasing; intermediate and stable in Ottawa and elsewhere • IDU: high in Ottawa; lower elsewhere appears to be decreasing in Ottawa and Toronto • HR heterosexual: Incidence apparently increasing in Ottawa

  14. Interpretation • Number of discordant samples and HIV tests by exposure category modeled • Since persons who test may not be representative and data quality is inconsistent, true HIV incidence and HIV prevalence cannot be derived directly from data • Thus,interpretation of HIV incidence must incorporate knowledge of patterns in HIV test seeking behaviours; measured HIV incidence likely higher than true incidence

  15. 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

  16. Acknowledgements • At the HIV Laboratory • Lisa Santangelo and Cindi Farina, data collection • Lynda Healey, detuned assay • Elaine McFarlane, data entry screens • Len Neglia, mail-out of questionnaires • Regional PHLs, mail-out of negative questionnaires • Physicians who prescribe HIV testing and provide supplementary data • Ontario HIV Treatment Network and the Centre for Infectious Disease Prevention and Control, Health Canada for funding

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