Rapid Molecular Detection of SARS-CoV-2 (COVID-19) Virus RNA Using Colorimetric LAMP

Yinhua Zhang; Nelson Odiwuor; Jin Xiong; Luo Sun; Raphael Ohuru Nyaruaba; Hongping Wei; Nathan A Tanner

With this preliminary evaluation of potential LAMP primer sets, the best performing sets (ORF1a-A, GeneN-A) were shared and synthesized in Wuhan for testing with actual COVID-19 samples. RNA was extracted from swabs using the standard laboratory protocol (see Materials and Methods) and RNA tested in colorimetric RT-LAMP alongside a commercial RT-qPCR assay. In addition to controls, a total of 7 patient RNA samples were tested, 6 of which were determined to be positive by RT-qPCR using ORF1a primers (C q 25-36.5, Table 2 ) and 4 positive with Gene N primers. One sample was negative by both RT-qPCR primer sets. When these samples were tested in the colorimetric LAMP assay, all 6 RT-qPCR positive samples showed visible color change indicating positive amplification, while the single RT-qPCR negative samples maintained pink color and was judged negative (Figure 4 ). Thus the colorimetric LAMP assay showed 100% agreement with the RT-qPCR results across a range of C q values. Although a small number of samples were tested here, the colorimetric LAMP assay enables reliable SARS-CoV-2 detection without sophisticated instrumentation, matching the RT-qPCR performance in field and point-of-care settings.