Publication:

Potential application of the hematology analyzer XN-31 prototype for field malaria surveillance in Kenya

Early and accurate diagnosis is a key component in malaria control programs. Microscopy is the current gold standard, however it requires extensive training and the results largely rely on the skill of the microscopists. Malaria rapid diagnostic tests (RDT) can be performed with minimal training and offer timely diagnosis, but results are not quantitative. Moreover, some Plasmodium falciparum parasites have evolved to evade detection by RDT. Developed by the Sysmex Corporation, the XN-31 prototype (XN-31p) is an automated hematology analyzer capable of detecting Plasmodium-infected erythrocytes and providing species differentiation and stage specific parasite counts in venous blood samples in a minute without any sample preparation. Here we tested the performance of the XN-31p with capillary blood samples and evaluated the effect of sample storage time and temperature on the stability of results. Paired capillary and venous blood samples were collected from 169 outpatients with clinical malaria symptoms in Homa Bay County Referral Hospital, Kenya. Malaria infections were diagnosed with the XN-31p, microscopy, RDT, and PCR. Capillary blood samples were remeasured on the XN-31p after 24 hours of storage at either room (15 to 25°C) or chilled temperatures (2 to 8°C). Identical results in malaria diagnosis were observed between venous and capillary blood samples processed with the XN-31p. The sensitivity and specificity of XN-31p with capillary blood sample relative to PCR were 0.857 and 1.000 and those relative to microscopy and RDT were 1.000 and 0.986 to 1.000, respectively. Parasitemia and complete blood count (CBC) results were stable in capillary blood samples after 24 hours at room or chilled temperatures. These results showed that the XN-31p can be a useful tool to complement existing methods for routine malaria diagnosis in remote settings.