Positive control wells: a potential answer to remote-area quality assurance of malaria rapid diagnostic tests

Malaria rapid diagnostic tests (RDTs) are a potential breakthrough in the provision of accurate diagnosis in remote areas, but widescale use is hampered by uncertainty over accuracy under field conditions. Positive control welts, which contain recombinant malaria parasite antigen, are a novel method for addressing this need for quality assurance. The potential of a commercially available positive control well, reconstituted with blood, was assessed for use in routine monitoring of RDT sensitivity in a remote malaria-endemic region. When maintained at 4 C, the wells produced a consistent level of parasite Lactate dehydrogenase (pLDH) antigen activity, as detected by pLDH-detecting RDTs, but activity reduced after cumulative exposure to temperatures likely to be encountered over a few months in a malaria-endemic area. This Limitation was successfully overcome in the field through centralized, controlled storage. Monitoring of RDT sensitivity was successfully incorporated into routine supervisory visits to remote clinics. However, improved temperature stability of the welts would enhance their potential. The threshold at which the welts' signal reduced RDT sensitivity requires further investigation. The welts show potential to overcome an important obstacle to the wide implementation of accurate parasite-based diagnosis and appropriate treatment. Further assessment of their place in malaria management is warranted. (c) 2005 Royal Society of Tropical Medicine and Hygiene. Published by Elsevier Ltd. All rights reserved.