Detection of Plasmodium vivax and Plasmodium falciparum using colorimetric loop-mediated isothermal amplification from dried blood spots collected in active and passive malaria surveillance in the Peruvian Amazon.

Abstract

Background: As malaria transmission declines in regions approaching elimination, highly sensitive diagnostic tools are needed to detect low-density infections, particularly in active and passive surveillance settings. Loop-mediated isothermal amplification (LAMP) is a promising molecular alternative to conventional diagnostics. This study evaluated the performance of a colorimetric LAMP (cLAMP) assay for detecting Plasmodium vivax and Plasmodium falciparum from dried blood spots (DBS) in the Peruvian Amazon.

Methodology/principal findings: The cLAMP assay was applied to DNA extracted from DBS collected through active case detection (ACD; n = 574) and passive case detection (PCD; n = 431). Two extraction methods were compared: mini spin column (MSC DNA) and a boil-and-spin (BS DNA) method. Diagnostic performance was evaluated against microscopy and real-time quantitative PCR (qPCR). In ACD samples, qPCR identified 125 malaria-positive cases (117 P. vivax, 8 P. falciparum). Microscopy showed a sensitivity of 57.6%, compared with 63.2% for cLAMP using BS DNA and 82.4% using MSC DNA. In PCD samples, qPCR detected 140 positives (129 P. vivax, 9 P. falciparum, and 2 mixed infections). Microscopy sensitivity was 72.9%, while cLAMP reached 77.1% with BS DNA and 82.1% with MSC DNA. Specificity remained high (> 99.0%) across methods.

Conclusions/significance: cLAMP improved the detection of malaria infections from DBS compared with microscopy when combined with column-based DNA extraction in active surveillance activities. While the boil-and-spin method showed performance comparable to microscopy, column-based extraction substantially increased sensitivity, especially for low-density infections identified through active surveillance. These findings support cLAMP as a practical and sensitive complementary tool for malaria surveillance in low-transmission and elimination settings.