Standardization and performance of SARS-CoV-2 RT-LAMP detection: a reliable, inexpensive, and alternative diagnostic...

The emergence of SARS-CoV-2 marked the onset of the COVID-19 pandemic, which has challenged public health worldwide. Mass testing performed by different assays represents an essential strategy to control virus spread, especially in low-income regions. This study aimed to standardize and validate RT-LAMP as an alternative tool for SARS-CoV-2 detection. Different sets of primers were assessed in silico and in vitro, and the N2 target was selected for the validation stage. The extracted RNA from the clinical samples was used to standardize the RT-LAMP fluorometric assay with BST 3.0 and RT enzymes, and the colorimetric assay was performed with WarmStart^® Colorimetric LAMP Master Mix. Clinical samples were also subjected to the Wondfo 2019-nCoV antigen test. The proposed protocols showed robust diagnostic accuracy in high-viral-load samples (C_T ≤ 30), 98.25% sensitivity and 90.91% specificity for fluorometric assay, and 92.98% sensitivity and 100% specificity for colorimetric assay. Considering the two visualization techniques, the fluorometric technique yielded more accordant results. In contrast, the rapid antigen test presented a lower performance, with 82.46% sensitivity and 100% specificity in samples with a C_T score ≤ 30. RT-LAMP visualization with a simple ultraviolet light source showed high sensitivity in active infection patient samples. The faster and simplest execution, cost-effectiveness, and accessible interpretation of the results are favorable points for improving this diagnostic tool as a potential screening tool for active transmission of COVID-19, especially in regions with limited financial resources.