A Comparative Assessment of the EIA/PCR HIV Test Results among Weakly Reactive Samples on Any of Determine HIV1/2, Statpak and Unigold Rapid Test Kits

Abstract

Objective: The Government of Uganda recommends the serial HIV rapid testing algorithm where weakly reactive results on any of the three: Determine, Statpak and Unigold are interpreted as positive. We assessed the proportion of weak positive (WP) rapid results against confirmed results. Methods: We generated cross tabulations using Stata 3.0 to compare the WP rapid test results on each kit in the algorithm against final results on EIA/PCR to assess the proportion of samples confirmed to be HIV negative on ELISA and/or qualitative DNA PCR. We also generated Positive Predictive Values (PPV) to find the proportion of results that were true positives. Results: A total of 231 weak positive (WP) results were selected. 71 were WP on Determine HIV1/2, 149 on Statpak and 11 on Unigold. We found that 35.2% of the WP results on Determine were confirmed Negative by EIA/PCR test with a Positive Predictive Value (PPV) of 64.8%, 80.5% of WP on Statpak were confirmed negative with a PPV of 19.5% while 63.6% of the WP on Unigold were confirmed negative with a PPV of 36.4%. When using the National serial rapid HIV testing algorithm, WP on both Determine and Statpak are scored as positive. However, we found that out of the 11 WP on both Determine and Statpak for screening and confirmatory tests respectively, 45.5% returned a final negative result with a PPV of 54.5%. Conclusion: Since point of care results are interpreted following manufacturer’s instructions, a substantial proportion that would have been scored as positive end up with Negative results. WP screening results whether using parallel or serial testing algorithm, need to be confirmed by EIA or PCR before results are finalized. This calls for a reevaluation of the national algorithm that considers WP scores instead of what is instated in the kit insert.