Clinical evaluation of lateral flow Mologic malaria P.f Ag (LDH) Rapid Diagnostic Test diagnostic accuracy: A cross-sectional study, Sudan 2020-2021

Background Malaria diagnosis by Rapid Diagnostic Test (RDTs) is challenged by the newly emerging histidine-rich protein 2 (HRP2) gene deletion in the Plasmodium falciparum species. The alternative lactate dehydrogenase (LDH)-dependent RDTs suffer from low sensitivity, and improvement in the sensitivity of LDH RDTs is the cornerstone for detecting (HRP2) gene deletion species. This study aimed to evaluate a novel improved Mologic LDH-dependent RDT for the diagnosis of P. falciparum malaria in partnership with FIND, Switzerland. Methods This is a descriptive cross-sectional study evaluating the clinical performance of improved Mologic P. falciparum LDH RDTs in two rural sites in Khartoum state, Sudan. Five hundred patients presenting with symptoms suggestive of malaria in the two primary care health centers were included after signing an informed consent. On-site microscopy screening, resulting in positive P. falciparum parasites or negative results, was included. Exclusion criteria included children under 5 years old, microscopy-positive P. vivax malaria, and severely ill patients. Finger-prick blood was collected for examination with microscopy, the index Mologic RDT, the comparator RDT, and preparation of DBS blood for nested PCR. Nested PCR was used as a reference method. The tests of microscopy and RDTs were performed by different lab personnel, blinded to each other's results. Results The mean age of the study subjects was 31 years, ranging from 5 to 80 years. Out of 500 patients, 210 were positive by PCR, 200 by expert microscopy, 193 by index Mologic RDT, and 199 by comparator RDT. The sensitivities of microscopy, index RDT, and comparator RDT were 95.24% (95% CI, 91.4–97.6), 91.9% (95% CI, 87.3–95.2), and 93.81% (95% CI, 89.6–96.6), respectively. All tests were nearly 100% specific for the detection of P. falciparum parasites. The concordance test (κ) showed more than 0.929 for all the tests. Seven samples were P. falciparum HRP2 Ag negative and were detected by Mologic RDT. Conclusions The novel Mologic P f LDH RDT showed performance concordant with standard expert microscopy and the comparator P f HRP2 Ag RDT. The lower sensitivity of the Mologic P f RDT, although not significant, makes it suitable for the clinical management of P. falciparum HRP2-negative malaria.