 Being a screening test, the results should be evaluated on the basis of confirmatory tests like PCR testing or western blot.One inherent advantage of an antigen test over an antibody test (such as antibody-detecting rapid HIV tests) is that it can take time for the immune system to develop antibodies after infection begins, but the foreign antigen is present right away.Although any diagnostic test may have false negatives, this latency period can open an especially wide avenue for false negatives in antibody tests, although the particulars depend on which disease and which test are involved.