Time to Become Negative of Three Rapid Diagnostic Tests for Malaria

Background: Antigen-detecting rapid diagnostic tests (RDTs) for malaria provide the possibility of a parasite-based diagnosis in areas where good quality microscopy can not be achieved. P. falciparum tests targeting the histidine-rich protein (HRP2) antigen are generally more sensitive than tests targeting the Plasmodium lactate dehydrogenase (pLDH) antigen. However, as the HRP2 antigen is eliminated from the bloodstream more slowly than the pLDH antigen, HRP2-based tests can give a positive result two weeks or more after the patient has taken an effective treatment, while pLDH tests generally turn negative a few days after. The use of an RDT positive result in a routine patient care is therefore challenged by the interpretation of whether the result is due to a lasting effect of the already treated infection or to a new infection. The interpretation might also be affected by the level of malaria transmission in the area. Objective: The objective of this study is to estimate the proportion of positive tests in patients successfully treated for malaria (smear negative) at different time points in time after treatment, for three rapid diagnostic tests: SD Bioline Malaria Antigen P.f. (catalogue number: 05FK50-02-4), CareStart Malaria HRP2 (Pf) (catalogue number: G0141) and CareStart Malaria pLDH (PAN) (catalogue number: G0111). The study will be carried out in two settings with known low and high malaria transmission levels in order to provide guidance of interpretation of a RDT positive result depending on the intensity of malaria transmission. Secondary objectives will be to measure the sensitivity and specificity of the malaria rapid tests compared to smear microscopy, to estimate the median time to become negative for each of the tests and to estimate the proportion of positive tests and the median time to become negative according to the initial parasitaemia and the presence of gametocytes.