Considerations

Fourth-generation tests are extremely sensitive and specific. They are more reliable in detecting early infection than most rapid tests. They are appropriate to use when immediate provision of results is not necessary, and when people are likely to come back for their results.

For testing after recent exposure, HIV RNA tests do have a slightly shorter window period, but have other disadvantages. Another alternative would be to use a test for p24 antigen only. However combining p24 and antibody in the same assay makes the test easier to perform.

Fourth-generation tests can be performed on a large number of samples at one time. However the need to have enough samples to perform a batch of tests may be a disadvantage in some settings.

Laboratories require sophisticated equipment and trained staff, as well as transport infrastructure to get the specimens to the lab. Clerical rigour is essential to make sure the right patients get the right test results.

Because testing is handled by a central lab, quality control programmes are easier to implement.