Q: I have read that an ELISA test is not specific. It may detect antibodies other than HIV having similar characteristics or some other antibody altogether. Is it true and should one go in for a direct virus testing through PCR test? What is the cost of this PCR test in India? Are tonsils resistant to HIV antibody within 3 to 6 months or do they kill the T cells after exposure. Does ELISA test check for both HIV-1 and HIV-2 in one test or different tests for these are better?

A:There are several reasons that one should never rely upon a single HIV test if it is positive. Always have a second or even a third test done. However, a negative test if done at least 3 months after exposure is very reliable and indicates that HIV infection is not present. In rare cases the window period may extend to longer than 3 months so a test is also recommended at 6 months where there is a definite history of exposure. The test kits now in use in India are sensitive to both HIV 1 and HIV 2, therefore separate tests are not needed. The tonsils are not the only site in the body for lymphocytes.