Authors

NJ van Dijk¹; Z Piets¹; S Menting¹; HD Schallig¹; PF Mens¹;  ¹ Amsterdam UMC, Netherlands

Discussion

Point-of-care diagnosis of malaria is currently based on microscopy and rapid diagnostic tests. However, both techniques have their constraints, including poor sensitivity for detection of low parasite densities. Hence, more accurate diagnostic tests for field use and routine clinical settings are warranted. The miniature direct-on-blood PCR nucleic acid lateral flow immunoassay (mini-dbPCR-NALFIA) is an innovative, easy-to-use molecular assay for the diagnosis of malaria in resource-limited settings. Unlike other simplified molecular methods, such as LAMP, the mini-dbPCR-NALFIA does not require DNA extraction and makes use of a handheld, portable thermal cycler that can be powered with a solar-charged power pack. Reading of results is done using a rapid lateral flow strip enabling differentiation of Plasmodium falciparum and non-falciparum malaria infections. Laboratory validation was performed to assess the performance of the mini-dbPCR-NALFIA for the diagnosis of pan-Plasmodium and P. falciparum infections in whole blood. Diagnostic accuracy was determined by testing a set of confirmed Plasmodium-positive blood samples from returned travellers (n=29), and confirmed Plasmodium-negative blood samples from returned travellers with suspected malaria (n=28), the Dutch Blood Bank (n=19) and intensive care patients at the Amsterdam University Medical Centers (n=16). The overall sensitivity and specificity of the assay were determined at 96.6% (95% CI, 82.2% - 99.9%) and 96.8% (95% CI, 89.0% - 99.6%). The limit of detection for P. falciparum was two parasites per microlitre of blood, as measured in dilution series of three P. falciparum-positive clinical blood samples. The repeatability of the assay was 92.0%. In conclusion, the mini-dbPCR-NALFIA is a sensitive, specific and relatively easy method for accurate detection of Plasmodium infections in whole blood and differentiation of P. falciparum. A phase-3 field trial is being performed to evaluate the potential implementation of this assay in malaria control programmes in both high- and low-transmission settings.