Comparison of the indirect immunofluorescence assay with western blot for the detection of HIV antibody.

ABSTRACT

With the increase in the prevalence of human immunodeficiency virus (HIV) infection in India, there is an urgent need to explore cost-containing methods of HIV antibody detection. We compared the indirect immunofluorescence assay (IFA) with the widely used but expensive confirmatory test, the Western blot (WBT). A panel of sera comprising 42 WB positive, 46 antibody negative (27 ELISA negative and 19 ELISA reactive but WB negative) and 58 sera with indeterminate WB profiles were tested by a commercial IFA kit. The sensitivity of IFA was found to be 97.6 per cent and specificity 97.8 per cent. Of the indeterminate sera, 18 (31%) were positive in IFA while 26 (45%) were negative and 14 (24%) were equivocal. In general, the IFA positivity was associated with the presence of the gag and env antibodies of HIV while negativity associated with the presence of lone antibodies. The cost of testing by IFA is less than 20 per cent of that of WB testing. Thus IFA appears to be a cost-containing alternative to WB in centres in India where immunofluorescent microscopy is routinely done.