Parasites that have deleted the HRP2 gene slip past the most common malaria RDTs. Here is what that means for the tests you stock.
Most malaria RDTs in the field detect histidine-rich protein 2, a marker that is abundant, stable, and cheap to target. The problem is that Plasmodium falciparum strains carrying deletions of the pfhrp2 and pfhrp3 genes produce genuine infections that this marker cannot see. The line stays blank on a patient who is, in fact, infected.
Where these deletions circulate — and the affected regions are expanding — an HRP2-only stock has a structural blind spot that no amount of careful reading corrects. The test is not broken; it is detecting a protein the parasite no longer makes. For the full specification, see our guide to rapid diagnostic tests.
The procurement answer is to stock combination tests or pLDH-based RDTs in regions with documented deletion prevalence, and to maintain a microscopy backstop for the clinically convincing case that the RDT calls negative. This is a stocking decision driven by local genomics, not a one-size-fits-all order.
International Health Journal flags HRP2-deletion prevalence as a first-order variable in malaria RDT procurement. The right test is the one that can see the parasite actually circulating in your catchment.