Close

HIV P24 Ag/Ab Test, Duo Test, Combo Test at our Clinic

SD-Bioline-Combo-Test

Info leaflet for SD Bioline Combo Test

I have been getting a lot of question with regards to the Duo test or Combo test as it is also known as.

Let’s first get some basics right:

Duo Test = Combo Test = P24 Ag/Ab test

All these terms refer to the same thing. Basically it is a test that simultaneously tests for the HIV P24 Antigen and the HIV antibody.

The HIV P24 antigen is a small piece of protein that is found on the capsule of the HIV virus. When a person is infected with HIV, these bits of protein can be found floating in the blood. The HIV P24 test is a test that detects these bits of protein. This test was first developed as a HIV screening test but rapidly ran out of favor due to the development of more advanced NAAT tests. The window period for P24 testing is also very small. This test alone is only accurate for between 3 and 6 weeks post exposure. So it is a test with very limited applications unless combined with the HIV antibody test. The presence of P24 Antigens in the blood indicates a recent HIV infection.

We all already know that the HIV antibody test becomes quite reliable at 4 weeks and as good as conclusive at 6 weeks. Although most health authorities still recommend a 3 months window period. So putting these 2 tests together gives you a very powerful tool to diagnose HIV infection in as little as 3 weeks. Personally I prefer to conduct the Combo test at 4 weeks because I believe that is when the level of P24 antigen peaks in the blood giving us maximum accuracy.

In our clinic, we use the SD Bioline Rapid HIV Combo Test 2.0. It is a rapid test that takes only 20 minutes for us to get results. We are also approved to conduct this test as part of the Anonymous HIV testing Program.

The test is conducted very much like the HIV antibody test. All we need is blood from a finger prick.

Positive-Combo-Test

SD Bioline HIV Combo Test showing a positive result (2 red bars)

False-Positive-Combo-Test

 
SD Bioline Combo HIV test showing a positive result. Note the test line is very faint. This could be due to a very recent HIV infection or the test could be false positive (1% chance).

Multicentre clinical trials have shown 100% sensitivity and more than 99% specificity.

So the Combo Test has many advantages including:

1. Earlier detection of HIV infection.

2. Rapid (20 minutes)

3. Anonymous

HIV-window-Period
Click on the picture for the latest information on the HIV testing Window Period