Abstract
BackgroundGlobally, there are over 200 million cases of malaria annually and over 400,000 deaths. Early and accurate detection of low-density parasitaemia and asymptomatic individuals is key to achieving the World Health Organization (WHO) 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 asymptomatic individuals.MethodsHere, an imaging-based sensing technique, particle diffusometry (PD), is combined with loop mediated isothermal amplification (LAMP) on a smartphone-enabled device to detect low levels of parasitaemia often associated with asymptomatic malaria. After amplification, PD quantifies the Brownian motion of fluorescent nanoparticles in the solution during a 30 s video taken on the phone. The resulting diffusion coefficient is used to detect the presence of Plasmodium DNA amplicons. The coefficients of known negative samples are compared to positive samples using a one-way ANOVA post-hoc Dunnett’s test for confirmation of amplification.ResultsAs few as 3 parasite/µL of blood was detectable in 45 min without DNA extraction. Plasmodium falciparum parasites were detected from asymptomatic individuals’ whole blood samples with 89% sensitivity and 100% specificity when compared to quantitative polymerase chain reaction (qPCR).ConclusionsPD-LAMP is of value for the detection of low density parasitaemia 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.
Highlights
There are over 200 million cases of malaria annually and over 400,000 deaths
particle diffusometry (PD)‐loop mediated isothermal amplification (LAMP) comparison in phone and microscope LAMP reactions targeting the 28 s rRNA gene were performed across tenfold serial dilutions from 3 × 104 to 3 × 100 DNA copies/μL of P. falciparum DNA
Negative template control (NTC) samples remained at baseline throughout the 45-min amplification for all instances in the quantitative polymerase chain reaction (qPCR) graphs (N = 4) (Additional file 1: Figure S1)
Summary
There are over 200 million cases of malaria annually and over 400,000 deaths. And accurate detection of low-density parasitaemia and asymptomatic individuals is key to achieving the World Health Organization (WHO) 2030 sustainable development goals of reducing malaria-related deaths by 90% and eradica‐ tion in 35 countries. Despite the World Health Organization’s (WHO) strategic goal to eradicate malaria in 10 countries and reduce global incidence by 40% by 2020, malaria cases have increased in the past several years [2, Colbert et al Malar J (2021) 20:380. One contributing factor to the disproportionate number of malaria cases in sub-Saharan Africa is delayed or inaccurate results along with a lack of access to malarial diagnostic tools that are practical for field use [4]. There is a need for portable, prompt, and easy-to-use diagnostic tools to decrease mortality from such a curable and preventable disease [5]
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