Enhanced detection of gametocytes by magnetic deposition microscopy predicts higher potential for Plasmodium falciparum transmission

Individuals with Plasmodium falciparum malaria symptoms (n = 55) provided samples for conventional blood smear (CBS) and magnetic deposition microscopy (MDM) diagnosis. Standard Giemsa staining and light microscopy was performed to evaluate all preparations. Plasmodium falciparum parasitaemia observed on MDM slides was consistently higher than parasitaemia observed by (CBS) for ring (CBS = 2.6 vs. MDM = 3.4%; t-test P-value = 0.13), trophozoite (CBS = 0.5 vs. MDM = 1.6%; t-test P-value = 0.01), schizont (CBS = 0.003 vs. MDM = 0.1%; t-test P-value = 0.08) and gametocyte (CBS = 0.001 vs. MDM = 0.4%; t-test P-value = 0.0002) parasitaemias. Gametocyte prevalence determined by CBS compared to MDM increased from 7.3% to 45%, respectively.MDM increased detection sensitivity of P. falciparum-infected, haemozoin-containing erythrocytes from infected humans while maintaining detection of ring-stage parasites. Gametocyte prevalence five-fold higher than observed by CBS suggests higher malaria transmission potential in PNG endemic sites compared to previous estimates.Reliable malaria diagnosis including qualitative and quantitative detection of all malarial blood stages remains very important in the campaign against this disease, which is believed to kill one to two million children annually [1]. Comparing diagnostic approaches that have included conventional blood smear (CBS) light microscopy, enzyme-based rapid diagnostic tests (RDTs) and PCR-based strategies has revealed a greater complexity of malaria infection in individuals and population studies [2]. Furthermore, direct comparisons of these methods illustrate differences in sensitivity and specificity, cost and efficiency of diagnosis. These comparisons show that no single diagnostic approach can be used to satisfy all malaria diagnostic expectations. Whereas RDTs can be performed rapidly in the field or by highly sensitive and specific PCR-based processing in well-equipped laboratories, these methods lose the ability to