HIV testing facilitates diagnosis of HIV infection after a client has received counseling services but it should be noted that test results may come out true or false. A True test result may be a true positive or a true negative while a false test result may be a false negative or a false positive
A false negative result is failure to correctly identify an HIV-infected person as HIV-positive.
A false positive result is an incorrect HIV-positive diagnosis in a person who is not actually infected.
True positive and true negative results are correct identifications of the presence and absence of HIV, respectively.
The ideal HIV screening test would correctly identify all HIV-positive and HIV-negative individuals 100% of the time but the available methods do not achieve 100% accuracy.
False negative results are most likely to occur during the window period that is when antibodies (substances produced by the body to neutralize the virus) and antigen (body parts of the virus) are not yet present at detectable levels in the sample to be tested. This takes from 3 weeks to several months and very rarely up to a year! After exposure to the virus
Conversely, false positive results may occur if non-HIV antibodies are incorrectly identified as antibodies to HIV. This could be due to other current viral infections in the individual being tested other than HIV. This scenario may also simulate miraculous HIV infection cure, in that, a client will seem to be HIV positive, and then resort to spiritual healing through prayer or witchcraft, and then after go for another HIV test, which will accurately show that the individual is indeed HIV negative!
Other causes of false results may be due to poor sample collection or processing, use of expired or wrong test kits. This contribute a very small percentage of wrong results
Because of the risk that a positive result from a single test is, in fact, a false positive, many doctors prefer to talk about the result being ‘reactive’ rather than ‘positive’. The result will need to be replicated in confirmatory testing before an HIV-positive diagnosis can be made.