Loop-mediated isothermal amplification (LAMP) for point-of-care detection of asymptomatic low-density malaria parasite carriers in Zanzibar.

Jackie Cook,Ali K Abass,Andreas Mårtensson,Iveth J González,David Bell,Elin Edlund,Majda H Nassor,Anders Björkman,Mwinyi Msellem,Abdullah Ali,Berit Aydin-Schmidt

doi:10.1186/s12936-015-0573-y

Abstract

BackgroundAsymptomatic, low parasite density malaria infections are difficult to detect with currently available point-of-care diagnostics. This study piloted a loop-mediated isothermal amplification (LAMP) kit for field-friendly, high-throughput detection of asymptomatic malaria infections during mass screening and treatment (MSAT) in Zanzibar, a malaria pre-elimination setting.MethodsScreening took place in three known hotspot areas prior to the short rains in November. Finger-prick blood was taken for screening by rapid diagnostic test (RDT) and LAMP and collected on filter paper for subsequent polymerase chain reaction (PCR) analyses. LAMP results were compared to RDT and to PCR using McNemar’s test.ResultsApproximately 1,000 people were screened. RDT detected ten infections (1.0% (95% CI 0.3-1.6)) whilst both LAMP and PCR detected 18 (1.8% (95% CI 0.9-2.6)) infections. However, PCR identified three infections that LAMP did not detect and vice versa. LAMP testing was easy to scale-up in field conditions requiring minimal training and equipment, with results ready one to three hours after screening.ConclusionsDespite lower than expected prevalence, LAMP detected a higher number of infections than the currently used diagnostic, RDT. LAMP is a field-friendly, sensitive diagnostic test that could be useful for MSAT malaria campaigns which require quick results to enable prompt treatment.

Highlights

Asymptomatic, low parasite density malaria infections are difficult to detect with currently available point-of-care diagnostics
The LoopampTM MALARIA Pan/Pf kit has been trialled in Europe [11,12] and in a health facility setting in Uganda [13], but not in the high-throughput manner required for mass screening and treatment (MSAT)
This study, based in Zanzibar, aimed to pilot the kit as the diagnostic tool in a routine MSAT intervention and to assess its practicality and performance for detection of malaria infection compared to rapid diagnostic test (RDT) and polymerase chain reaction (PCR)

Summary

Methods

Study site and population Zanzibar is a semi-autonomous archipelago, located 35 km from the coast of mainland Tanzania. Blood samples for three different malaria diagnostics were taken from a single finger-prick: 5 μl for RDT (using the collection device provided in the kit), 60 μl for LAMP (using a plastic capillary tube (Dropstir, Medical Precision Plastics, USA)) and approximately 50 μl spotted directly onto filter paper (Whatman 3MM) for PCR. Staff training and logistics Two laboratory technicians employed by Zanzibar Malaria Elimination Programme with no previous experience of LAMP and limited experience of molecular methods were trained for three days to perform DNA extraction and the LAMP assay. LAMP samples from Panga Tupu were transported at ambient temperature 1 km by car to a nearby health facility, equipped with electricity, for processing Data analysis This was an explorative study to test LAMP in a highthroughput manner as well as determine its sensitivity and specificity. Ethical approval was obtained from the Zanzibar Medical Ethical Committee (ZAMEC) (ZAMREC/0001/September/013) and from the Regional Ethics Review Board, Stockholm, Sweden (2013/836-32)

Results

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