Introduced in 2009, the Determine HIV-1/2 Ag/Ab Combo test looks for both antibodies and p24 antigen, in a similar way to antibody/antigen laboratory tests. At the time of writing, it is the only point-of-care test to do so.

Because it detects p24 antigen as well as antibodies, the window period should be reduced. The manufacturer says the window period is an average of five days shorter than for the previous Determine test, but this varies from individual to individual (range: 2 to 20 days). The manufacturer also reports that on tests with 1179 positive and 2343 negative samples, sensitivity was 100% and specificity was 99.2%.

However, other research suggests that while the test performs well in respect of established HIV infection, its ability to detect recent HIV infection does not match that of laboratory antibody/antigen tests. Clinicians in London, Sydney and San Francisco have each reported that for people with either acute or recent infection, the test is only able to detect between 50 and 90% of infections. Whereas Determine has excellent detection of antibodies, it frequently fails to identify p24 antigen that can be detected with laboratory tests. Studies from Malawi, Zambia and Rwanda have shown particularly low rates of antigen detection, suggesting problems with sensitivity to the range of HIV-1 subtypes that are found in African people living in the UK. For example, of 34 people with acute infection in Zambia and Rwanda, the rapid test detected p24 antigen for only one person (sensitivity 3%) and detected HIV infection (either via p24 antigen or antibodies) in only eight cases (sensitivity 23.5%).