Towards the Use of a Smartphone Imaging-Based Tool for Point-of-Care Detection of Asymptomatic Low-Density Malaria Parasitemia

Abstract Background: Globally, there are over 200 million cases of malaria annually and over 400,000 deaths. Early and accurate detection of low density parasitemia and asymptomatic individuals is key to achieving the WHO’s 2030 sustainable development goals of reducing malaria-related deaths by 90% and eradication in 35 countries. Current rapid diagnostic tests are neither sensitive nor specific enough to detect the low parasite concentrations in the blood of some asymptomatic individuals. Methods: Here, we combine an imaging-based sensing technique, particle diffusometry (PD), with loop mediated isothermal amplification (LAMP) on a smartphone-enabled device to detect low levels of parasitemia often associated with asymptomatic malaria. After amplification, PD quantifies the Brownian motion of fluorescent nanoparticles in the solution during a 30 second video taken on the phone. The resulting diffusion coefficient is used to detect the presence of Plasmodium DNA amplicons by comparing to coefficients of negative samples using a one-way ANOVA test.Results: As few as 1 parasite/µL of blood was detectable in 45 minutes without DNA extraction. We detected Plasmodium falciparum (P. falciparum) parasites from asymptomatic individuals’ whole blood samples with 89% sensitivity and 100% specificity when compared to quantitative polymerase chain reaction (qPCR). Conclusions: PD-LAMP is of value for the detection of low density parasitemia especially in areas where trained personnel may be scarce. The demonstration of this smartphone biosensor paired with the sensitivity of LAMP provides a proof of concept to achieve widespread asymptomatic malaria testing at the point of care.