Screening strategies and laboratory assays to support Plasmodium falciparum histidine-rich protein deletion surveillance: where we are and what is needed

Abstract

Rapid diagnostic tests (RDTs) detecting Plasmodium falciparum histidine-rich protein 2 (HRP2) have been an important tool for malaria diagnosis, especially in resource-limited settings lacking quality microscopy. Plasmodium falciparum parasites with deletion of the pfhrp2 gene encoding this antigen have now been identified in dozens of countries across Asia, Africa, and South America, with new reports revealing a high prevalence of deletions in some selected regions. To determine whether HRP2-based RDTs are appropriate for continued use in a locality, focused surveys and/or surveillance activities of the endemic P. falciparum population are needed. Various survey and laboratory methods have been used to determine parasite HRP2 phenotype and pfhrp2 genotype, and the data collected by these different methods need to be interpreted in the appropriate context of survey and assay utilized. Expression of the HRP2 antigen can be evaluated using point-of-care RDTs or laboratory-based immunoassays, but confirmation of a deletion (or mutation) of pfhrp2 requires more intensive laboratory molecular assays, and new tools and strategies for rigorous but practical data collection are particularly needed for large surveys. Because malaria diagnostic strategies are typically developed at the national level, nationally representative surveys and/or surveillance that encompass broad geographical areas and large populations may be required. Here is discussed contemporary assays for the phenotypic and genotypic evaluation of P. falciparum HRP2 status, consider their strengths and weaknesses, and highlight key concepts relevant to timely and resource-conscious workflows required for efficient diagnostic policy decision making.

Impact of malaria diagnostic choice on monitoring ofPlasmodium falciparumprevalence estimates in the Democratic Republic of the Congo and relevance to control programs in high-burden countries

“…Parasite prevalence and malaria incidence are usually estimated using the results of RDTs, the primary malaria diagnostic method used for case management in the DRC and across sub-Saharan Africa. However, high-throughput molecular and serological assays are becoming more readily available throughout the region for surveillance [24]. Malaria programs will increasingly have access to results from advanced laboratory approaches and need empirical data to guide their decision-making.…”

“…Though imprecise, these numbers approximate how diagnostic choice would influence prevalence estimates across 402 health areas within 35 health zones in Kinshasa Province (Fig Saharan Africa. However, high-throughput molecular and serological assays are becoming more readily available throughout the region for surveillance [24]. Malaria programs will increasingly have access to results from advanced laboratory approaches and need empirical data to guide their decision-making.…”

Correction: Screening strategies and laboratory assays to support Plasmodium falciparum histidine-rich protein deletion surveillance: where we are and what is needed

“…Following publication of the original article [ 1 ], the authors requested the following corrections: Page 6 (of the PDF)—This sentence needs revision: “In addition to pfhrp2/3, the three assays published to date target different parasite genes: pfldh [37], pfrnr2e2 [38], and cytb [39]”. In this sentence, change “cytb” to “pfbtub”.…”

Plasmodium falciparum withpfhrp2/3deletion not detected in a 2018-2021 malaria longitudinal cohort study in Kinshasa Province, Democratic Republic of the Congo

“…16 We used this parasite density threshold to reduce the risk of unintentional misclassification of deletions in the setting of low DNA concentrations. 17,18 Positive calls required cycle threshold (C t ) values < 35. Samples positive for HumTuBB and pfldh but negative for pfhrp2 or pfhrp3 were subjected to a confirmatory real-time PCR targeting the P. falciparum beta-tubulin ( PfBtubulin ) gene.…”