Reptitive results- potisitive ELISA, negative WESTERN BLOT? any reasons why?!
Question:
Reptitive results- potisitive ELISA, negative WESTERN BLOT? any reasons why?
Answers:
When you submit your blood for HIV antibody testing, it is first tested using ELISA. The ELISA test is very sensitive and can therefore have false positives, but if the ELISA test is negative it is considered accurate, as the likelihood of a false negative on an ELISA test is very very rare.
The Western Blot test is done next if the results to the ELISA were indeterminate, or positive. The Western Blot is very specific and the chances of having a false negative are very very rare.
Various things may cause a false positive on a single HIV laboratory test. But when a person is tested for HIV, multiple independent laboratory tests are used. The separate laboratory tests catch each other's errors, so the HIV test result for the person is highly accurate. The chance of a false positive in a low-prevalence setting is about 1 in 250,000. For more, see Chou et al, Annals of Internal Medicine, 5 July 05, vol 143, #1, p 55-73.