Histidine Rich Protein 2-Based Malaria Rapid Diagnostic Testing in Sentinel Sites of Gabon: Impact of Epidemiological Context and Microscopy Capacity

Abstract

Introduction: Rapid diagnostic tests (RDTs) that detect the histidine-rich protein 2 (HRP2) antigen are fundamental to malaria diagnosis in sub-Saharan Africa. However, their diagnostic performance can vary depending on the epidemiological context, local operational conditions, including laboratory capacity, personnel expertise and quality assurance. This study aimed to evaluate the performance of HRP2-based RDTs in sentinel sites across Gabon, and to identify factors associated with positive test results. Methods: A cross-sectional study was conducted among 447 patients recruited from multiple sentinel sites. Light microscopy of Giemsa-stained thick blood films was used as the reference standard. Malaria prevalence, diagnostic performance indicators (sensitivity, specificity, positive and negative predictive values, and overall accuracy) and discrepancies between diagnostic methods were estimated. Univariate and multivariable logistic regression analyses were performed to identify factors independently associated with HRP2-RDT positivity. Results: Malaria prevalence was 32.2 % according to microscopy and 43.4 % according to the HRP2-RDT. The overall sensitivity of the RDT was 84 %, with substantial variability between sites, ranging from 66% in Melen to 100% in Mouila. Specificity also varied substantially, reaching 95% in Melen and decreasing to 58 % in Oyem. The positive and negative predictive values were 66% and 89 %, respectively, giving an overall diagnostic accuracy of 79%. Among patients with a negative HRP2-RDT result, 10.7 % had a malaria infection confirmed by microscopy. The overall discordance rate between the two diagnostic methods was 21 %, primarily observed in Oyem and Moanda. Multivariable analysis revealed that patients attending health facilities in Mouila, Oyem and Bitam had a significantly higher likelihood of testing positive by HRP2-RDT than those in Melen. Conclusion: The diagnostic performance of HRP2-based RDTs varied significantly across sentinel sites, with an overall rate of discordance of 21.0 %. These findings highlight the need for cautious interpretation of RDT results and for strengthening diagnostic capacities, particularly microscopy, within malaria surveillance systems in Gabon.