I tested for HIV with PCR 10 days after suspected contact, and HIV was not detected. Now after about 3 months and 10 days i tested for HIV using the ELISA test and again it was NOT DETECTED. Is it necessary to test using Western BLot and what are my chances of testing positive after 3 more months or lesser?

It is not necessary to use Western Blot testing when you have a negative/non-reactive ELISA/EIA. The ELISA is a highly sensitive, front-line test that is extremely unlikely to be falsely negative. However, the ELISA test is not specific enough to confirm HIV infection. The Western Blot test is considered a gold-standard "confirmatory test," meaning that it is a highly specific test that should only be used after a positive ELISA. It is highly unlikely that the Western Blot would yield a false positive result. The Western Blot test is not used as a front-line test because it is more likely to be "indeterminate" in the absence of a screening test.

HIV antibody testing should be have greater than 99% accuracy after three months have elapsed since exposure.

RMK