Causes of false-negative rapid diagnostic tests for symptomatic malaria in the DRC

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ABSTRACT Background The majority of Plasmodium falciparum malaria diagnoses in Africa are made using rapid diagnostic tests (RDTs) that detect histidine-rich protein 2. Increasing reports of false-negative RDT results due to parasites with deletions of the pfhrp2 and/or pfhrp3 genes ( pfhrp2/3 ) raise concern about existing malaria diagnostic strategies. We previously identified pfhrp2- negative parasites among asymptomatic children in the Democratic Republic of the Congo (DRC), but their impact on diagnosis of symptomatic malaria is unknown. Methods We performed a cross-sectional study of false-negative RDTs in symptomatic subjects in 2017. Parasites were characterized by microscopy; RDT; pfhrp2/3 genotyping and species-specific PCR assays; a multiplex bead-based immunoassay; and/or whole-genome sequencing. Results Among 3,627 symptomatic subjects, we identified 427 (11.8%) RDT-/microscopy+ cases. Parasites from eight (0.2%) samples were initially classified as putative pfhrp2/3 deletions by PCR, but antigen testing and whole-genome sequencing confirmed the presence of intact genes. Malaria prevalence was high (57%) and non-falciparum co-infection common (15%). HRP2-based RDT performance was satisfactory and superior to microscopy. Conclusions Symptomatic malaria due to pfhrp2/3 -deleted P. falciparum was not observed in the DRC. Ongoing HRP2-based RDT use is appropriate for the detection of falciparum malaria in the DRC.

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