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.

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.