AP BIOLOGY

Detailed explanation-1: -While many HIV tests are extremely accurate, they do not achieve 100% accuracy. A false negative is a test result that says a person does not have HIV when, in fact, they do. False negative results most often occur when people test in the first few weeks after infection, during the ‘window period’ of a test.

Detailed explanation-2: -What does a negative HIV test result mean? A negative result doesn’t necessarily mean that you don’t have HIV. That’s because of the window period-the time between HIV exposure and when a test can detect HIV in your body.

Detailed explanation-3: -The third study, from Tanzania, reported three false-negative cases, including a single case of a woman who was experiencing symptoms associated with HIV and several opportunistic infections and who tested HIV-negative but was in fact HIV-positive (27).

Detailed explanation-4: -Test inaccuracy HIV tests are generally highly accurate but may produce a small number of false-positive results. The CDC states that HIV tests have 99.6% specificity. This means that for every 1, 000 people without HIV who take the test, 996 will receive true negative results, and four may receive a false positive.

Detailed explanation-5: -If 1, 000 uninfected people are tested with an HIV test and 4 have false-positive results, the HIV test’s specificity is 99.6% (996 true negative test results/1, 000 HIV uninfected persons tested).