The sensitivity of the OptiMAL rapid diagnostic test to the presence of Plasmodium falciparum gametocytes compromises its ability to monitor treatment outcomes in an area of Papua New Guinea in which malaria is endemic.

Using in vivo samples from treatment failure malaria cases, we demonstrate the high sensitivity of the parasite lactase dehydrogenase (pLDH)-based OptiMAL rapid diagnostic test in the detection of P. falciparum gametocytes. This high sensitivity limits the use of pLDH-based tests in the monitoring of treatment outcomes in circumstances where gametocytemia is common.