HIV Diagnosis in Resource Constrained Setting: How Good Is the Current Algorithm?

Background: The conventional HIV testing algorithm in most of the developed countries consists of two tests: an HIV enzyme immunoassay capable of identifying HIV-1 and HIV-2 antibodies and a confirmatory HIV-1 Western blot or immunofluorescence assay. However, the current algorithm for HIV diagnosis in India uses three sequential antibody assays. There has always been doubt regarding the benefits of this algorithm. Objective: To determine the utility of the current diagnostic algorithm and to find out the proportion of indeterminate or discrepant results. Methods: Retrospective analysis of HIV antibody testing data was carried out over a period of five years after institutional ethics committee approval. The specimens positive with the screening test and negative with both the supplemental tests were labeled as discrepant. Specimens positive with any of the two tests (screening and one of the supplemental tests) and negative with the remaining supplemental test were labeled as indeterminate. These indeterminate specimens were confirmed by immunoblotting. Results: A total of 141,296 samples were tested. Of these, 71 (0.05%) samples were indeterminate and 292 (0.21%) were discrepant. Western blot was done on 60 indeterminate samples of which 10 (16.67%) were positive for HIV 1 antibodies, 14 (23.33%) were negative for HIV antibodies and 36 (60%) had indeterminate result. Conclusion: In view of the low numbers of indeterminate and discrepant results, the current algorithm appears to be appropriate in our resource constrained setting. However, the algorithm for HIV testing should also include DNA PCR testing facility to resolve western blot indeterminate results.