Two-Stage Detection of Plasmodium spp. by Combination of Recombinase Polymerase Amplification and Loop-Mediated Isothermal Amplification Assay.

We developed a combination of recombinase polymerase and loop-mediated isothermal amplification methods (RAMP) for rapid screening of five human Plasmodium spp. simultaneously. RAMP is a two-stage isothermal amplification method, which consists of a first-stage recombinase polymerase amplification and a second-stage loop-mediated isothermal amplification. Under these two isothermal conditions, five Plasmodium spp. were amplified in less than 40 minutes. We demonstrated RAMP assay with 10-fold better limit of detection than a single (loop-mediated isothermal amplification) LAMP. As compared with microscopy, RAMP assay showed 100% sensitivity (95% CI: 95.65-100.00%) and 100% specificity (95% CI: 69.15-100.00%). The end products were inspected by the color changes of neutral red. Positive reactions were indicated by pink while the negative reactions remained yellow. The combination assay established in this study can be used as a routine diagnostic method for malaria.