HIV Antibody/Antigen

Infection DiagnosticsBlood

The HIV antibody/antigen test (often called fourth-generation) looks for both antibodies the body makes against HIV and the p24 antigen the virus produces. Combining the two extends the window in which infection can be detected.

Why it matters: A non-reactive result indicates HIV is not detected at the time of testing. A reactive result triggers confirmatory testing, since first-line tests can rarely produce false positives. Result interpretation typically pairs with clinical follow-up.

What Moves It

May increase with:

HIV infection
Acute seroconversion

May decrease with:

Antiretroviral therapy
Associated Conditions
AIDSHIV/AIDS
Related Markers
CD4 countViral load
Common questions

What is HIV Antibody/Antigen?

The HIV antibody/antigen test (often called fourth-generation) looks for both antibodies the body makes against HIV and the p24 antigen the virus produces. Combining the two extends the window in which infection can be detected.

What might a high or low HIV Antibody/Antigen mean?

A non-reactive result indicates HIV is not detected at the time of testing. A reactive result triggers confirmatory testing, since first-line tests can rarely produce false positives. Result interpretation typically pairs with clinical follow-up.

What can affect HIV Antibody/Antigen?

It may be higher with: HIV infection, Acute seroconversion. It may be lower with: Antiretroviral therapy.

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