Usefulness of Malachite-Green LAMP for Diagnosis of Plasmodium and Five Human Malaria Species in a Nonendemic Setting

Abstract

ABSTRACT. Molecular methods are necessary to detect low-density malaria infections. The purpose of this study was to assess the diagnostic performance of six malachite-green loop-mediated amplification method (MG-LAMP) assays (MG-LAMP-Pf, MG-LAMP-Pv, MG-LAMP-Po, MG-LAMP-Pm, MG-LAMP-Pk, and MG-LAMP-Pspp) for the species-specific detection of each human Plasmodium, including P. knowlesi, and the Plasmodium genus compared with the nested-multiplex malaria polymerase chain reaction (NM-PCR), using 161 malaria-positive and 274 malaria-negative samples. MG-LAMP-Pspp assay detected the five human Plasmodium species and each species-specific MG-LAMP assay detected only its corresponding species. Sensitivity, specificity, and predictive values of MG-LAMP assays, compared with NM-PCR, were > 90%, except in the case of the MG-LAMP-Pm assay, which dropped to 47%. Limit of detection for MG-LAMP-Pspp assay ranged from 0.1 parasites/µL for P. falciparum to 16.9 parasites/µL for P. malariae samples, and it was similar for the rest of MG-LAMP assays except for the MG-LAMP-Pm assay. Turnaround time was estimated to be 2 hours and 35 minutes for one MG-LAMP assay and 4 hours and 15 minutes if all species-specific MG-LAMP is set up, whereas for the NM-PCR, turnaround time was ∼6 hours and 15 minutes. Costs per determination ranged from 1 to 6 euros for MG-LAMP assays and 5 euros for NM-PCR. Therefore, MG-LAMP assays appear to have good concordance compared with the reference method, except for the MG-LAMP-Pm assay. They can detect low parasitemia and identify malaria species, with lower costs and shorter time to obtain results, and they are suitable tools to be used in endemic and non-endemic countries for malaria detection.