Performance and usability evaluation of three LDH-based malaria rapid diagnostic tests in Kedougou, Senegal

BackgroundThe emergence of pfhrp2/3-deleted parasites threatens histidine-rich protein 2 (HRP2)-based malaria rapid diagnostic test (RDT) performance. RDTs targeting Plasmodium falciparum (Pf) lactate dehydrogenase (LDH) may address current product limitations and improve case management. ObjectivesTo evaluate the performance and usability of three LDH-based RDTs in febrile patients. MethodsA cross-sectional diagnostic accuracy study was conducted in Kedougou, Senegal. Capillary blood was tested using the SD Bioline Ag Pf (#05FK50) and three LDH-based RDTs: BIOCREDIT Malaria Ag Pf (pLDH), BIOCREDIT Pf (pLDH/HRPII), and BIOCREDIT Pf/Pv (pLDH/pLDH) (Rapigen Inc., Republic of Korea). Venous blood was collected to repeat the BIOCREDIT RDTs and conduct microscopy. Frozen venous specimens were tested using a reference PCR assay. A quantitative multiplex malaria antigen assay measured antigen concentration. RDT performance was determined and analyzed as a function of antigen concentration distribution. Usability of the Pf-only BIOCREDIT tests was evaluated using a questionnaire. Results154/220 participants (70%) were Pf-positive by PCR. The Pf (pLDH/HRPII) test demonstrated the highest sensitivity at 78% (70.9%-84.5%); specificity was 89% (79.4%-95.6%). All RDTs performed better than microscopy (53% sensitivity). RDTs performed better when compared to antigen concentration over PCR results. Improved sensitivity of the Pf (pLDH/HRPII) test was driven by the HRP2 line. Line intensity correlated with antigen concentration. Predicted sensitivity using the analytical limit of detection (LOD) was comparable to observed sensitivity. RDTs demonstrated acceptable usability. ConclusionsBoth HRP2 and LDH contributed to the sensitivity of the best-performing Pf-RDT. RDT analytical LODs can be used to predict performance in populations with known antigen concentrations.