A nurse is talking with a client who has come to the clinic for HIV testing. The nurse should explain that, after the laboratory has the enzyme-linked immunosorbent assay (ELISA) results, it will use which of the following tests to confirm the diagnosis?

Choice A rationale The CD4+ T-cell count is a measure of immune function, not a confirmatory diagnostic test for HIV infection itself. These lymphocytes are the primary target of the HIV virus, and their count typically declines as the disease progresses, with a normal range generally 500 to 1,500 cells/mm. A low CD4+ count indicates immunodeficiency but is used for staging and monitoring, not confirmation. Choice B rationale The quantitative RNA assay, also known as the viral load test, measures the number of HIV RNA copies in the blood. While it is highly specific and sensitive for diagnosing acute infection and monitoring treatment effectiveness, it is not the standard confirmatory test after a positive ELISA, which is typically an antibody-based screening. The viral load is crucial for disease management. Choice C rationale The viral load test is the quantitative RNA assay described in Choice B. It measures the amount of active HIV replication and is key for predicting disease progression and assessing antiretroviral therapy success. However, the ELISA screens for HIV antibodies, and the confirmation test seeks to specifically confirm the presence of these or other viral proteins. Choice D rationale Western blot analysis is the traditional, more specific test used to confirm positive or indeterminate results from an initial ELISA or rapid antibody screening test. It detects antibodies to specific, individual HIV proteins, ensuring the initial positive result was not a false positive due to cross-reacting antibodies. This high specificity confirms the presence of HIV infection