What is the confirmatory test for HIV after screening?

The confirmatory test for HIV after an initial screening is the Western blot test. This test is used to confirm the presence of HIV antibodies in the blood following a positive result from preliminary screening tests, which may include enzyme-linked immunosorbent assay (ELISA) or rapid tests. The Western blot is highly specific and can distinguish between the presence of HIV antibodies and non-specific antibodies that may result from other infections or conditions.

The Western blot works by separating proteins from the HIV virus and detecting antibodies specifically against these proteins, providing confirmation of an HIV infection. This level of specificity makes it the gold standard confirmatory test, ensuring robust and accurate diagnosis.

Other testing methods mentioned serve different roles. While ELISA is primarily used for initial screening, rapid tests offer the convenience of quick results but may not provide definitive confirmation. CD4 tests, meanwhile, measure the number of CD4 cells in the blood and are used to monitor the immune status of a person living with HIV rather than for diagnosis. Thus, the Western blot stands out as the appropriate choice for confirming an HIV diagnosis following preliminary screenings.