Loop-mediated isothermal amplification (LAMP) is a simple yet powerful nucleic acid amplification methodology to identify Plasmodium parasite DNA in a highly sensitive manner. Commercially available malaria LAMP kits are however limited to Pan or P. falciparum specific assays only. To address this limitation, FIND has been supporting the development of a P. vivax specific LAMP kit in collaboration with Eiken Chemical. The first analytical and clinical evaluations of this kit are reported here.
Prototype P. vivax LAMP kits were designed and produced by Eiken Chemical. Analytical evaluation experiments were conducted at the Hospital for Tropical Diseases using well characterized clinical samples. The same prototype kits were used for clinical performance evaluation in retrospective and prospective studies conducted in Peru and Colombia in febrile individuals suspected of malaria.
Using serial dilutions of P. vivax samples, the LAMP kit showed a limit of detection of 1 parasite/µL, similar to the Pan LAMP kit, and no cross-reactivity when tested with non-vivax Plasmodium samples. The kit showed a sensitivity and specificity of 93.8% [95%CI: 91.2% – 96.4%] and 92.9% [90.1% - 95.7%] respectively, as compared to PCR, in a prospective study conducted in Colombia (n=208). It showed a sensitivity and specificity of 84.6% [95%CI: 78.4% – 86.6%] and 92.0% [88.8% - 94.5%] respectively, as compared to PCR, in a retrospective study conducted in Peru (n=560).
The P. vivax LAMP kit described here shows adequate analytical and clinical performance, in line with existing LAMP kits, and will complement currently available products to facilitate the detection of P. vivax infections in endemic countries enabling the use of appropriate species-specific treatments, including radical cure for P. vivax infections.