Fig. 3  Detection of SARS-CoV-2 RNA using the RT-LAMP assay.
(A) Scatter plot shows a comparison of RT-LAMP assay results and RT-qPCR results for RNA samples tested on 10 96-well plates. The RNA extraction method (QC, QiaCube, a column-based method; QS, QiaSymphony, a bead-based method) is indicated. The time point for measurement by the colorimetric RT-LAMP assay was 30 min after the start of the 65°C incubation. The 96-well plate shown in Fig. 2 is not included here. Table 1 shows numbers of samples stratified according to the results of the RT-LAMP and the RT-qPCR assays. (B) Sensitivity (right) and specificity (left) of the RT-LAMP assay [derived from data in (A) and Table 1] are shown. The specificity is the fraction of RT-qPCR–negative samples correctly identified as negative by the RT-LAMP assay. For sensitivity, the RT-qPCR–positive samples were stratified by CT values into three bins (as indicated by x axis labels), and for each bin, the sensitivity is given as the fraction of qPCR-positive samples in the respective CT bin that have also given a positive result in the RT-LAMP assay. The thick black lines indicate the values of these fractions (i.e., the specificity and sensitivity estimates); the black boxes indicate the corresponding 95% confidence intervals (Wilson’s binomial confidence interval). (See also table S2).