Title: Trends in HIV incidence in Ontario based on the detuned assay: Update to December 2002
1Trends 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
2Introduction
- 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
3Study 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
4Data 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
5Laboratory 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)
6Study questionnaires mailed and returned,
October 1999 to December 2002
2,187 2,440 4,627
7Exposure category classification according to
HIV test requisition, returned questionnaires
and modeled distribution, HIV-positives
8HIV incidence (per 100 person-years) for selected
exposure categories by health region
Tested
22,535 370 13,853 14,366 257,343
9MSM HIV incidence by six-monthperiod and
region,Ontario, October1999-December 10th 2002
10IDU HIV incidence by six-month period and
region,Ontario,October1999- December 10th 2002
11High risk heterosexuals HIV incidence by
six-month period and region, Ontario,October1999-D
ecember 10th 2002
12Low risk heterosexuals HIV incidence by
six-month period and region, Ontario,
October1999-December 10th 2002
13Summary 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
14Interpretation
- 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
15Conclusions
- 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
16Acknowledgements
- 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