Diagnostic accuracy of loop-mediated isothermal amplification (LAMP) for screening patients with imported malaria in a non-endemic setting.

Camille Ponce,Véronique Potinet,Stéphane Picot,Karim Tazarourte,Bruno Simon,Etienne Javouhey,Marion Douplat,Patrick Miailhes,Yves Gillet,Thomas Perpoint,Flora Kaczorowski,Fatimata Sow,Anne-Lise Bienvenu,Adeline Lavoignat,Guillaume Bonnot,Laurent Jacquin,Alain Sigal

doi:10.1051/parasite/2017054

Abstract

Background: Sensitive and easy-to-perform methods for the diagnosis of malaria are not yet available. Improving the limit of detection and following the requirements for certification are issues to be addressed in both endemic and non-endemic settings. The aim of this study was to test whether loop-mediated isothermal amplification of DNA (LAMP) may be an alternative to microscopy or real-time PCR for the screening of imported malaria cases in non-endemic area. Results: 310 blood samples associated with 829 suspected cases of imported malaria were tested during a one year period. Microscopy (thin and thick stained blood slides, reference standard) was used for the diagnosis. Real-time PCR was used as a standard of truth, and LAMP (Meridian Malaria Plus) was used as an index test in a prospective study conducted following the Standards for Reporting Diagnosis Accuracy Studies. In the 83 positive samples, species identification was P. falciparum (n = 66), P. ovale (n = 9), P. vivax (n = 3) P. malariae (n = 3) and 2 co-infections with P. falciparum + P.malariae. Using LAMP methods, 93 samples gave positive results, including 4 false-positives. Sensitivity, specificity, positive predictive value and negative predictive value for LAMP tests were 100%, 98.13%, 95.51%, and 100% compared to PCR. Conclusion: High negative predictive value, and limit of detection suggest that LAMP can be used for screening of imported malaria cases in non-endemic countries when expert microscopists are not immediately available. However, the rare occurrence of non-valid results and the need for species identification and quantification of positive samples preclude the use of LAMP as a single reference method.

Highlights

The global malaria burden has been considerably reduced during the last decade thanks to insecticidetreated bed nets, rapid diagnosis tests (RDTs) and highly effective antimalarial treatment
The aim of this study was to test whether loop-mediated isothermal amplification of DNA (LAMP) may be an alternative to microscopy or real-time PCR for the screening of imported malaria cases in non-endemic area
Microscopy is recommended for malaria when its quality can be maintained and strong expertise is available

Summary

Introduction

The global malaria burden has been considerably reduced during the last decade thanks to insecticidetreated bed nets, rapid diagnosis tests (RDTs) and highly effective antimalarial treatment. Malaria remains a substantial global health problem [29] and elimination has been pointed out as a reachable goal in the few decades [16]. One of the major issues to be addressed on the way toward malaria elimination is the development of a highly sensitive, reliable and easy-to-perform method for the point-of-care diagnosis of malaria [3]. Biological diagnosis of malaria can be conducted using light microscopy, RDTs, PCR, or a combination of these methods. The requirements for certification of biological diagnosis have increased the need for efficient and standardized methods that are easy to perform for end-users and that are reliable when microscopic expertise is not immediately available

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Conclusion