This session focused on the utility of laboratory assays to monitor HIV incidence in various countries

Saphonn, Cambodia, presented data from a study of risk factors and HIV incidence at VCT site clients in Phnom Penh, Cambodia, 2006. The study assessed HIV incidence using the BED incidence (STARHS) assay and risk factors for incident infection in a cross-sectional sample of VCT clients in Phnom Penh, Cambodia. The annualized HIV incidence was 3.3%. There was a higher estimated HIV incidence among women than men (4.7% vs. 2.5%). Condom use with commercial sex workers was the only factor found to have an independent and significant association with recent HIV infection. In Cambodia, there has been limited incidence data. In combination with other surveillance system data incidence studies like this one will be important to monitor HIV trends in Cambodia.

Moyo, Botswana presented on a study to estimate HIV incidence among pregnant women attending antenatal clinics in Botswana in 2005.  Like the Cambodia study, the incidence was determined using a STARHS serological assay. Out of 2444 confirmed HIV positive specimens, 11% were classified as recent sero-converters. Using a window period of 180, the adjusted incidence among pregnant women was estimated to be at 8.1%. This incidence is very high and is of concern. When interpreting the results Moy commented that there is presently limited experience utilizing the STARHS methodology in HIV-1 subtype C prevalent regions.

Philip Cunningham, Sydney presented results on enhanced laboratory surveillance to determine the yield of acute HIV infection detection in an inner Sydney population of high risk men who have sex with men. Routine clinical samples that screened negative by a fourth generation HIV-1/2 antibody/antigen combination enzyme immunoassay were combined in pools of six samples each. Pooled samples were then tested for HIV-1 RNA using a qualitative nucleic acid amplification assay (NAAT). If the pool tested positive individual samples were tested. A total of 10,573 HIV negative samples in 487 pools were screened and three pools tested positive (0.1% of all samples).  Although the cost of RNA and nucleic tests are quite expensive, pooling reduces cost. Where funding permits, this strategy may useful to increases the identification of acute cases of HIV-1 infection.

Nabatov presented on the use of STARHS serological assays combined with molecular epidemiological data to estimate the rate of epidemiological and virological changes of HIV-infection in the Former Soviet Union (FSU) countries during a period where there was intravenous drug user (IDU) -associated HIV infection outbreaks. The findings included the following: (1) the pattern of high HIV-1 genetic diversity characteristic of the early epidemic changed to a concentrated one within 1 year in St. Petersburg and in Moscow; (2) different FSU regions were at different stages of the HIV-1 epidemic in 1994-1996; (3) the change of serotypic patterns characteristic of different stages of the HIV/AIDS epidemic for the non-IDU risk group occurred within 1 year in Moscow. The findings highlight the utility of these laboratory techniques to better understand the rapid change in HIV epidemiology in the FSU. The results suggest the IDU-associated epidemic pattern of HIV-1 epidemic in the FSU had high rate of spreading among other susceptible populations.

In all these sessions, the importance of using incidence data to evaluate the public health impact of prevention, care, and treatment initiatives were raised.