Is a HIV test done at 85 day after the intercourse and result is negative that valid?

Yes, an HIV test done 85 days after intercourse and resulting in a negative result is generally considered valid. The recommended window period for HIV testing is typically 4 to 6 weeks (28 to 42 days) after potential exposure. However, some sources recommend waiting up to 3 months (12 weeks) for conclusive results.

The 4th generation HIV tests, which are commonly used, can detect antibodies to HIV-1 and HIV-2 as well as the p24 antigen, which is a protein produced by the HIV virus. These tests are highly sensitive and specific, and a negative result after 85 days is usually considered reliable.

To ensure accuracy, it's important to get tested at a reputable healthcare facility or testing center. If there is any uncertainty or concern, you can consult a healthcare professional for further guidance and interpretation of the test results.