Serologic testing is employed to detect antibodies to the AIDS virus, which is currently identified by the term "human immunodeficiency virus (HIV)." The virus originally was named "human T-cell lymphotropic virus, type III (HTLV-III), a term that remains in common usage.

Antibodies may be detected by a variety of immunoassay techniques, the most common being an enzyme linked immunosorbent assay (ELISA). When an assay is reactive on initial testing, it should be repeated on the same specimen. A more specific test, (Western blot, immunofluorescent assay) is usually performed following repeatedly reactive ELISA results.

These tests may be covered when performed to help determine a diagnosis for symptomatic patients. They are not covered when furnished as part of a screening program for asymptomatic persons.

NOTE: Two enzyme-linked immunosorbent assay (ELISA) tests that were conducted on the same specimen must both be positive before Medicare will cover the Western blot test.