Accurate
malaria diagnosis has dual roles in identification of symptomatic persons for effective
malaria treatment and also enumeration of asymptomatic persons who contribute to the epidemiologic determinants of transmission. Three currently used diagnostic tests, microscopy, rapid diagnostic tests (RDTs), and real-time PCR, all have different sensitivities and specificities, which are parasite density dependent. Here, we compare their concordance among 451 febrile episodes in a cohort of 2,058 children and adults followed over 6 months in a region in central Tanzania with hypoendemic
malaria. Microscopy, a
histidine-rich
protein-based RDT, and two different real-time PCR gene probes detected Plasmodium falciparum in 20, 54, 41, and 78 episodes of
fever, respectively. They had complete concordance in only 9 episodes. Real-time PCR with an 18S probe was more sensitive than with a mitochondrial probe for
cytochrome b despite higher copy numbers of
mitochondrial DNA. Both PCR yields were increased 4-fold by
glycogen/
acetate precipitation with low-speed centrifugation. Duplicate PCR increases low-density
malaria detection. RDT had the highest number of unique positives, presumably from persistent
antigen despite the absence of parasites, although RDT did not detect 3
parasitemias with over 1,000 parasites/μl. In a latent class analysis, real-time PCR had significantly higher sensitivity than did microscopy or RDT. Agreement between real-time PCR, RDT, and microscopy was highest in March and April, when both the P. falciparum parasite rate and parasite densities are highest. Real-time PCR is more sensitive and specific than RDT and microscopy in low-prevalence, low-parasite-density settings.