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

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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

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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.lt4 months)
• Allows the calculation of HIV incidence density,
  an important indicator usually difficult to
  measure

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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

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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

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Laboratory methods

• Abbott 3A11 EIA kit modified as follows
• serum diluted to 120,000
• 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)

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Study questionnaires mailed and returned,
October 1999 to December 2002
2,187 2,440 4,627
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Exposure category classification according to
HIV test requisition, returned questionnaires
and modeled distribution, HIV-positives
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HIV incidence (per 100 person-years) for selected
exposure categories by health region
Tested
22,535 370 13,853 14,366 257,343
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MSM HIV incidence by six-monthperiod and
region,Ontario, October1999-December 10th 2002
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IDU HIV incidence by six-month period and
region,Ontario,October1999- December 10th 2002
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High risk heterosexuals HIV incidence by
six-month period and region, Ontario,October1999-D
ecember 10th 2002
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Low risk heterosexuals HIV incidence by
six-month period and region, Ontario,
October1999-December 10th 2002
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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

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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

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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

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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