Misclassification of HIV infection status among serologically diverse populations in Nigeria: implications for test and treat program.

Background: In 2015, the World Health Organization (WHO) launched the Test and Treat policy which supports antiretroviral treatment for all people with HIV, irrespective of CD4 count or clinical stage. This was adopted in 2016 in Nigeria. This policy resulted in scaleup of HIV testing strategies and differentiated models of care including community-based ART. This study evaluated the HIV testing algorithm and assessed the rates of misclassification of HIV status among newly diagnosed clients.

Methods: Between February and August 2018, whole blood samples were collected from clients newly diagnosed with HIV in Lagos and Benue states. HIV status wasconfirmed with rapid tests using the serial algorithm during outreach sessions for both key populations and general populations. HIV positivity was confirmed using GenScreen™ HIV1/2.O Antibody only ELISA test (BioRad, USA). Optical density (OD) for each sample was measured with the use of Emax microplate reader set at endpoint 450 wavelength. Based on manufacturer's algorithm, sample OD and calculated cut-off value ratio, an OD < 1.0 was interpreted as negative and > 1.0, positive. Concordance between rapid test algorithm result and ELISA was used to estimate the proportion of samples that were misclassified.

Results: A total of 788 samples were collected from newly diagnosed clients across 4 sites in Lagos and 3 sites in Benue. Samples were collected from 212 and 178 key populations (KPs) clients in Lagos and Benue, respectively, and from 206 and 192 general population (GPs) clients in Lagos and Benue, respectively. Mean OD was 3.75 (IQR:3.70-3.81) with a standard deviation of 0.13. There was a 100% concordance between rapid test and ELISA results and no misclassification identified.

Conclusion: We identified no instances of misclassification of positive HIV status suggesting that all clients who have been placed on treatment truly had HIV infection. The 100% concordance rate recorded from all the sites may be attributable to the maturity of the HIV program in Nigerian with a concomitant standard quality assurance system for both clinical and outreach testing services. This finding supports the implementation of the Test and Treat policy that Nigeria has adopted. Scale up of Test and Treat and community ART is thus recommended to increase access to treatment.