Evaluation of HIV antigen /antibody combination ELISAs for diagnosis of HIV infection in Dar Es Salaam, Tanzania

Abstract

Introduction: the aim of this study was to evaluate the performance of Enzygnost HIV Integral II antigen/antibody combination ELISAs in order
to formulate HIV ELISA testing algorithms for the Ministry of Health and Social Welfare, Tanzania.

Methods: this was a laboratory-based evaluation of Enzygnost HIV Integral II Antibody/ Antigen, Murex HIV antigen/antibody and Vironostika HIV Uniform II antigen/antibody conducted between October 2011 and May 2012.

Results: a total of 600 blood samples were included in the evaluation. A total of 209/596 (35.1%) serum samples were confirmed HIV positive. Of these, the prevalence of HIV infection was 2.3% (3/130), 2.3% (3/127), 2.2% (3/139) and 100% (200/200) for VCT clients, ANC attendees, blood donors and CTC patients, respectively. Three hundred and eighty seven (64.9%) were HIV negative samples. Sensitivity was 100% (95% CI; 98.3-100%) for all the three HIV ELISAs. The specificity for the Enzygnost HIV Integral II and Murex was 100% (95% CI; 99.1-100%). The final specificity at repeat testing was 99.5% (95% CI; 98.2-99.9%) for  Vironostika. Enzygnost HIV Integral II detected HIV infection seven days since first bleed.

Conclusion: initial testing using either Vironostika or Murex HIV   antigen/antibody combination ELISA followed by testing of reactive samples on the Enzygnost HIV Integral II gave a sensitivity and specificity of 100% with reduced window period. Combination of two HIV antigen/antibody  combination ELISAs can be used as an alternative confirmatory testing  strategy for screening of donated blood at the National and Zonal blood transfusion centres and in lab diagnosis of HIV infection.