The heat stability of Plasmodium lactate dehydrogenase-based and histidine-rich protein 2-based malaria rapid diagnostic tests

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Abstract
Malaria rapid diagnostic tests (RDTs) have performed well in a variety of studies, but recent reports have described sensitivity for Plasmodium falciparum as significantly lower than that required for operational deployment. Exposure to high temperature has been suggested as an explanation. This study assessed the temperature stability of two different Plasmodium lactate dehydrogenase (pLDH)- and three histidine-rich protein 2 (HRP2)-detecting RDTs. One HRP2 test proved insufficiently sensitive for assessment. After incubation at 35, 45 and 60 degrees C, two RDTs detecting pLDH showed a substantial fall in percentage test line positivity over time, which was not seen with the remaining two HRP-2-based RDTs. For the particular products studied, variability was high, with the pLDH-based RDTs being less sensitive than HRP2-based RDTs against the sample of P. falciparum used and more susceptible to heat-induced damage, but the reasons for this are unclear. The performance of malaria RDTs can be adversely affected at the temperatures to which they will be exposed when transported to, and used in, the rural tropics.