antiretroviral treatment and HIV prevention in Cameroon

Inaccurate diagnosis of HIV-1 group M and O is a key challenge for ongoing universal access to antiretroviral treatment and HIV prevention in Cameroon.

Increased access to HIV testing is essential in working towards universal access to HIV prevention and treatment in resource-limited countries. The authors evaluated currently used HIV diagnostic tests and algorithms in Cameroon for their ability to correctly identify HIV infections. They estimated sensitivity, specificity, and positive and negative predictive values of 5 rapid/simple tests, of which 3 were used by the national program, and 2 fourth generation ELISAs. The reference panel included 500 locally collected samples; 187 HIV -1 M, 10 HIV-1 O, 259 HIV negative and 44 HIV indeterminate plasmas. None of the 5 rapid assays and only 1 ELISA reached the current WHO/UNAIDS recommendations on performance of HIV tests of at least 99% sensitivity and 98% specificity. Overall, sensitivities ranged between 94.1% and 100%, while specificities were 88.0% to 98.8%. The combination of all assays generated up to 9% of samples with indeterminate HIV status, because they reacted discordantly with at least one of the different tests. Including HIV indeterminate samples in test efficiency calculations significantly decreased specificities to a range from 77.9% to 98.0%. Finally, two rapid assays failed to detect all HIV-1 group O variants tested, with one rapid test detecting only 2 out of 10 group O specimens. In the era of antiretroviral therapy scaling-up in Africa, significant proportions of false positive but also false negative results are still observed with HIV screening tests commonly used in Africa, resulting in inadequate treatment and prevention strategies. Depending on tests or algorithms used, up to 6% of HIV-1 M and 80% of HIV-1 O infected patients in Cameroon do not receive antiretroviral therapy and adequate counselling to prevent further transmission due to low sensitivities. Also, the use of tests with low specificities could imply inclusion of up to 12% HIV negative people in antiretroviral therapy programs and increase budgets in addition to inconveniences caused to patients.

False-positive and false-negative HIV test results have negative implications for both individuals and programmes – all efforts must be made to minimise them. The first step is to evaluate assay performance using a serum panel from patients infected with subtypes that are circulating locally and the second step is instituting ongoing quality control. Inadequate sensitivity (ability to correctly identify presence of infection) and specificity (ability to correctly identify lack of infection) mean that infections are missed which can delay treatment or, on the other hand, that people who are not infected believe that they are, with personal and programmatic costs. When test kits are chosen by officials on the basis of lower price rather than performance efficacy, the results can be dire. This article should be essential reading for all national laboratory directors .