Evaluation of the Loop Mediated Isothermal DNA Amplification (LAMP) Kit for Malaria Diagnosis in P. vivax Endemic Settings of Colombia

Abstract

BackgroundMost commonly used malaria diagnostic tests, including microscopy and antigen-detecting rapid tests, cannot reliably detect low-density infections which are frequent in low transmission settings. Molecular methods such as polymerase chain reaction (PCR) are highly sensitive but remain too laborious for field deployment. In this study, the applicability of a malaria diagnosis kit based on loop-mediated isothermal amplification (mLAMP) was assessed in malaria endemic areas of Colombia with Plasmodium vivax predominance.Methodology/Principal FindingsFirst, a passive case detection (PCD) study on 278 febrile patients recruited in Tierralta (department of Cordoba) was conducted to assess the diagnostic performance of the mLAMP method. Second, an active case detection (ACD) study on 980 volunteers was conducted in 10 sentinel sites with different epidemiological profiles. Whole blood samples were processed for microscopic and mLAMP diagnosis. Additionally RT-PCR and nested RT-PCR were used as reference tests. In the PCD study, P. falciparum accounted for 23.9% and P. vivax for 76.1% of the infections and no cases of mixed-infections were identified. Microscopy sensitivity for P. falciparum and P. vivax were 100% and 86.1%, respectively. mLAMP sensitivity for P. falciparum and P. vivax was 100% and 91.4%, respectively. In the ACD study, mLAMP detected 65 times more cases than microscopy. A high proportion (98.0%) of the infections detected by mLAMP was from volunteers without symptoms.Conclusions/SignificancemLAMP sensitivity and specificity were comparable to RT-PCR. LAMP was significantly superior to microscopy and in P. vivax low-endemicity settings and under minimum infrastructure conditions, it displayed sensitivity and specificity similar to that of single-well RT-PCR for detection of both P. falciparum and P. vivax infections. Here, the dramatically increased detection of asymptomatic malaria infections by mLAMP demonstrates the usefulness of this new tool for diagnosis, surveillance, and screening in elimination strategies.

Diagnosing Neglected Tropical Diseases in HIV Coinfection

“…[41][42][43] These reports showed that LAMP assays enable detection of P. falciparum and P. vivax at the species level and diagnose asymptomatic infections or low parasitic loads. 41,43,44 Molecular diagnosis may also facilitate the detection and identification of malaria cases in nonendemic countries, where individuals may become infected when traveling for business or tourism. Considering that HIV is widely distributed throughout the world, HIV-positive tourists can become infected.…”

Loop mediated isothermal amplification: a novel diagnostic tool for malaria elimination

“…Several NATs, including quantitative PCR (qPCR) combined with microfluidics [24], and those linked to enzyme-linked immunosorbent assays [25][26][27] as well as non-nucleic acid techniques [28][29][30] are in development for the purposes of malaria diagnosis but are not discussed further here.…”

“…The alternative to ACD, for the purpose of malaria elimination, is mass drug administration (MDA) [29,30] which alleviates the issue of missed infections. However, the issues associated with MDA are complex-there is a negative historical precedent for MDA in malaria eradication efforts and the most appropriate choice of antimalarial agent is uncertain given that artemisinin combination therapy (ACT) is an effective schizontocidal drug but does not clear gametocytemia while primaquine is gametocidal and effective again P. vivax hypnozoites but is associate with hemolysis in persons with glucose-6-phosphate dehydrogenase (GDPD) deficiency [23,31].…”

“…LAMP has been used for the detection of P. falciparum using crudely extracted DNA from whole blood [22], or using a rapid boil and spin method [23]. Subsequently, LAMP has been used to identify all Plasmodium species [24] including Plasmodium knowlesi [25,26], and LAMP primers have been optimized to improve the sensitivity with which P. falciparum [23,27] and P. vivax [28,29] can be detected. Commercially available Loopamp kits (Eiken Chemical co)…”

“…Plasmodium genus and P. falciparum have been found to perform well in regional health facilities, but were not capable of specifically detecting P. vivax [28,29] . Furthermore, for specific detection of P. vivax, the three LAMP assays published to date have had low analytic sensitivity, with reported detection limits of 100 plasmid copies/ µL for 18s rRNA target [23]( which was equivalent to 500 parasites/ µL when tested by Patel et.al [30]), 125 parasites/µL for Pvr64 target (highly conserved repeat region in P. vivax genome) [30] and 100 copies/ µL for alpha-tubulin target [31].…”