What it measures
Antibodies to HIV-1 and HIV-2, the two types of the virus. Unlike a fourth-generation test, it does not look for the p24 antigen, so it picks up a new infection later. Some rapid tests work this way.
Why people test it
- Checking for HIV as part of a sexual health screen.
- Checking after a possible exposure, once enough time has passed for antibodies to appear.
- Routine screening for some jobs or before some medical procedures.
Typical range
There is no numeric range. The result is reported as reactive or non-reactive (sometimes positive or negative), and a reactive result is confirmed with further tests before a diagnosis is made. The report shows how that lab reports it.
Finger-prick or vein?
A finger-prick sample is usually fine for an antibody test like this, and some providers offer a home kit. Others take blood from a vein at a clinic.
An antibody-only test has a longer window period than a fourth-generation test, as the p24 antigen appears before antibodies do.