American Association of Critical-Care Nurses (AACN) Certification Practice Test

What confirms the HIV diagnosis with a specificity of 99.9%?

1. PCR test

2. CD4 count

3. Western blot

4. Rapid test

The correct answer is: Western blot

The Western blot test is considered the confirmatory test for an HIV diagnosis due to its high specificity of 99.9%. This means that when the Western blot test is positive, there is a very low chance of false positives, making it a reliable indicator of true HIV infection. It serves as a secondary step following an initial screening test, typically an enzyme immunoassay (EIA), which may yield false positive results. The Western blot test analyzes specific proteins of the HIV virus to identify antibodies produced by the immune system in response to the infection. This test's detailed methodology and ability to differentiate between HIV variants contribute to its reliability. While PCR tests and rapid tests are also utilized in diagnosing HIV, they do not achieve the same level of specificity as the Western blot. PCR is more sensitive and used to detect the actual viral load rather than antibodies, while rapid tests, while convenient, may have varying accuracy rates. The CD4 count, although important in monitoring the progression of HIV and the immune system's health, does not confirm the presence of the virus itself.