Rapid diagnostic tests for malaria: are they sufficiently reliable?

Abstract ◆ Malaria causes significant mortality and morbidity worldwide and is one of the major infectious diseases affecting the health of deployed Australian Defence Force personnel. ◆ Malaria rapid diagnostic tests (RDTs) offer great potential for early and accurate diagnosis of maal ra,i especially in remote areas. Many RDTs are now commercially available; however, their sensitivities have been reported to be variable. ◆ In this article, we examine the advantages and limitations of current malaria RDTs, analyse possible causes of the variations in sensitivity, and summarise our investigation of the effect of parasite antigen diversity on the sensitivity of RDTs that detect Plasmodium falciparum histidine-rich protein 2 (PfHRP2). ◆ At parasitaemias 250parasites/ μ L (enough to make a malaria-naive person ill), a proportion of patients may return a negative PfHRP2-based RDT result because of the infecting parasite carrying a “non-sensitive” gene encoding an HRP2 protein that is not detected by the kit at sufficiently high sensitivity. Patients with persisting symptoms should have repeated tests at a later time, and microscopy should be used if at all possible.