Fever is common in malarial areas, and getting the diagnosis right (ie deciding if it is due to malaria or other causes) and treating correctly helps save lives, particularly in children. The World Health Organization (WHO) now recommends that all patients with fever suspected of being malaria are properly diagnosed before any treatment begins. This ensures that highly effective antimalarial drugs such as artemisinin-based combination treatments (ACTs) are properly used to prevent unnecessary treatments, untoward risks, and resistance developing.
Standard diagnosis of malaria in the past has depended on blood microscopy, but this requires a technician and a laboratory, and is often not feasible for basic health services in many areas. Sometimes in research studies, another technique called polymerase chain reaction (PCR) is used, but again this requires equipment and trained staff, and cannot be used routinely. Technological advances have led to rapid diagnostic tests (RDTs) for malaria. These detect parasite-specific antigens in the blood, are simple to use, and can give results as a simple positive or negative result, within 15 minutes.
This review evaluates the accuracy of RDTs compared with microscopy and PCR for detecting Plasmodium falciparum parasites in the blood. It includes 74 studies, giving a total of 111 RDT evaluations (of which 104 compared RDTs with microscopy), reporting a total of 60,396 RDT results. Results are presented by type of test, classified by the malaria antigen that they are designed to detect (either histidine-rich protein-2 (HRP-2), or plasmodium lactate dehydrogenase (pLDH)).
The results indicate that RDTs can be very accurate compared to microscopy and PCR. The performance of RDT types varied but the differences were not large. HRP-2-based tests tended to be more sensitive (ie they identified more true cases of malaria) and less specific (ie they wrongly identified more malaria that was not present) than pLDH-based tests. Choice will depend on prevalence of malaria, and we provide data in this review to assist these decisions, although policy makers will also take into account other factors relating to cost and test stability.