AEGiS-14IAC: Monitoring HIV transmission in Australia using a detuned testing strategy.

14th International AIDS Conference

Barcelona, Spain - July 7-12, 2002

Monitoring HIV transmission in Australia using a detuned testing strategy.

Int Conf AIDS 2002 Jul 7-12; 14:(abstract no. MoOrC1044)

McDonald A, Cunningham P, Delpech V, Kaldor JM
National Centre in HIV Epidemiology and Clinical Research, Darlinghurst, Australia

BACKGROUND: In Australia, evidence of the recency of infection with HIV-1 is routinely collected through national surveillance for newly diagnosed HIV infection, based on a previous negative test or a diagnosis of primary infection. Because such information is only available on a limited number of cases, surveillance for recent HIV infection provides a lower bound to the actual extent of HIV transmission. We evaluated a detuned HIV antibody assay, to provide another indication of the extent of recent HIV infection among cases of newly diagnosed infection.

METHODS: Sera remaining from cases of HIV-1 infection newly diagnosed in central Sydney were tested with a detuned assay. Cases with a reactive result on the standard assay and a non-reactive result on the detuned assay were defined as cases of early HIV infection. Results from the detuned assay were compared with information on the recency of infection available through HIV surveillance.

RESULTS: Of 700 cases of HIV-1 infection, newly diagnosed from January 1998 to July 2001, 237 (33.8%) were identified as early infection whereas 172 (24.6%) had other evidence of recent infection (49 with a prior negative antibody test only, 44 had both a negative test and a diagnosis of primary infection and 79 had primary infection only within 12 months of HIV diagnosis). Sensitivity and specificity were 69.2% and 77.5%, based on a gold standard of a negative test or primary infection within 12 months of HIV diagnosis, and 75.5% and 73.9%, respectively, within a 3 month interval. Sensitivity and specificity was highest for cases with both a prior negative test and primary infection (86.4% among cases with 12 month interval). In 1998 - 2001, the percentage of HIV diagnoses with early infection remained relatively stable at around 33%.

CONCLUSION: Preliminary use of the "detuned" assay in central Sydney suggests that the method will have considerable value in monitoring HIV transmission.

Keywords: AEGIS, HIV Infections, HIV Seropositivity, HIV Antibodies, HIV-1, AIDS Serodiagnosis, Research Design, Sensitivity and Specificity, Australia, transmission, utilization, immunology, methods

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MoOrC1044