EVALUATION OF THE WORLD-HEALTH-ORGANIZATION ANTIBODY-TESTING STRATEGYFOR THE INDIVIDUAL PATIENT DIAGNOSIS OF HIV-INFECTION (STRATEGY-III)

Objective. To evaluate the World Health Organisation (WHO) antibody te sting strategy for the individual patient diagnosis of HIV infection ( strategy III), Design. Evaluation of a combination of enzyme-linked im munosorbent assays (ELISAs) for the detection of antibodies to HIV-1 a nd HIV-2 infection. The WHO strategy ill calls for a combination of th ree ELISAs, based on different antigens and/or differing test principl es, to be used in-a sequential fashion, The first part of the study ev aluated various kits as part of a selection process. The second part o f the study was an assessment of the three-ELISA testing strategy on r outine sera submitted to the National institute for Virology (NIV) for HIV testing, In all instances, the conventional testing protocol, whi ch utilises a screening ELISA followed by a confirmatory Western blot (WB) on positive specimens, was used as the 'gold standard'. Setting. The HIV-testing laboratory at the NIV, Johannesburg. Results. In the f irst part of the study, ail of the ELISA kits evaluated showed high se nsitivity and specificity, and a selection of the kits for part two of the study was made in accordance with the WHO recommendation. The kit s selected, in order of use, were the Biotest anti-HIV 1/2 (test 1), P asteur Genelavia Mixt HIV-1/2 (test 2) and Murex Wellcozyme HIV-I comp etitive assay (test 3). This combination was evaluated using 7 812 ser a submitted to the NIV for serology testing. The sensitivities of the tests were highly satisfactory (99,6 - 100%) as were the specificities (99,2 - 100%), The positive predictive value of strategy III at vario us seroprevalences (0,5 - 25,5%) was greater than or equal to 99,6%. T he rate of WE usage when compared with the previous HIV testing protoc ol was low (4,6%). Conclusions. The results of this study suggest that this testing protocol could be introduced in South Africa with consid erable cost-saving and no reduction in specificity.