Q: Is it possible that the first HIV test comes positive and a second test comes negative? When does this happen? How can there be a positive followed by a negative test? Kindly clarify?

A:Yes, it is possible that the first test comes positive and that a second, subsequent test gives a negative report. In such a case the negative test is to be believed. False positives are not rare, false negative tests are extremely unlikely. Always believe a negative report (after the window period), but do not believe an unconfirmed positive test.