This test can detect HIV even in people who

Polymerase Chain Reaction (PCR)

Whereas the ELISA and the Western blot detect the presence of antibodies to the virus, PCR detects the human immunodeficiency virus (HIV). This test can detect HIV even in people whoare not currently producing antibodies to the virus.

Specifically, PCR detects the presence of what is known as "proviral DNA." HIV is made up of a genetic material known as RNA, which is a slightly different type of material than DNA. Proviral DNA is a DNA copy of the RNA of the virus.

PCR is used:

• to confirm the presence of HIV when the ELISA and Western blot are negative;
• in the first few weeks following infection, before antibodies are detectable;
• if the Western blot is indeterminate;
• in newborns for whom the presence of their mothers' antibodies complicates the other tests.