Further evaluation of alternative strategy for HIV testing in India.

A total 320 sera from groups at risk for HIV were evaluated by two (198 specimens) or three (122 specimens) screening tests for confirmatory anti-HIV testing in comparison to Western Blot as gold standard. Sera positive by both screening tests showed 100% correlation with Western Blot although with a false positivity rate of 3.2%. In specimens positive by 1st screening test but negative by the second, (considered negative for anti-HIV antibody as per WHO algorithm), 8.7% were found to be Western Blot positive showing the serious problem of false negativity of the proposed WHO algorithm. Employing the system of three screening test systems did not provide additional benefit for the specimens positive by initial two screening tests since all of them were positive by third test also. However, the study involving three screening tests substantiated the need for Western Blot in discordant specimens (i.e. positive by first test but negative by second), since in this group one out of 22 (4.6%) such specimens were Western Blot positive. Considering the serious consequences of both false positive and false negative results, it is felt that alternative strategy of confirmatory anti-HIV serology, although economical may not be suitable substitute for Western Blot in India at this juncture when the prevalence of HIV infection is relatively low.