Hello, this is Dr. Love. The system says that you have requested a different expert.
A fourth generation HIV test at 8 weeks is very accurate, but it is not perfect, so it depends upon what information you are seeking from a test. Even at 4-6 weeks, an HIV test is very accurate. After a single encounter with someone of unknown HIV status, if there is a negative test at 4-6 weeks, the results are at least 99.999% accurate.
It is this level of accuracy that leads certain recommendations to say that if there is a negative test at 4-6 weeks, there is no need to perform additional testing. Obviously, a test at 8 weeks would be slightly better.
However, a test at 4-6 weeks is not quite 100%. With the current evidence, the only test that can be said to be 100% is an antibody test at 12 weeks (or 3 months). Since the more sensitive HIV antibody test was developed decades ago, there has never been a person that has become positive after a negative test at 12 weeks. A similar statement cannot be made for testing at 4-6 weeks or at 8 weeks.
It is the 100% accuracy at 12 weeks that is the basis for other recommendations that say that testing should be repeated at 12 weeks.
It is worth noting that the risk of a single encounter with someone of unknown HIV status is low, and the current recommendation is that no testing needs to be done after such an encounter. Instead of testing after each encounter with someone of unknown HIV status, the current recommendation is that there should be regular testing, and annual testing is appropriate for most individuals.
So, while testing after this encounter is not recommended, if you decide to be tested, a test at 8 weeks is very accurate, but if you want 100% accuracy, then the testing would need to be done at 12 weeks.
If I can provide any additional information, please let me know.