Comparison of RT-LAMP and RT-qPCR assays for detecting SARS-CoV-2 in the extracted RNA and direct swab samples

Abstract

Rapid detection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in infected patients is critical for infection control. Loop-mediated isothermal amplification (LAMP) has been demonstrated to be a rapid, simple, reliable, cost-effective and sensitive method to detect SARS-CoV-2 in a variety of samples in considerably less time than Real-Time PCR. In this study, we developed and optimized a rapid detection method for SARS-CoV-2 based on RT-LAMP method utilizing a specific primer set targeting the ORF1a gene and then examined its sensitivity and efficiency using a serially diluted viral RNA sample with a known concentration. Furthermore, the sensitivity of the RT-LAMP to detect SARS-CoV-2 in direct swab samples with varying Ct values were compared to a commercial molecular RT-qPCR based detection kit. According to our findings the optimal incubation time for RT-LAMP assay was 45 min. There was a complete agreement between RT-LAMP and RT-qPCR in diagnosing the viral genome in the diluted extracted RNA sample. However, it had a lower sensitivity (71%) to detect the viral genome in direct swab samples compared to RT-qPCR. In conclusion, due to its simplicity, rapidness, sensitivity, and specificity, RT-LAMP has tremendous potential as a point-of-care tool; nevertheless, more research is needed to utilize it for detecting SARS-CoV-2, particularly in direct swab samples.

Keywords: Direct assay; RT-LAMP; RT-qPCR; SARS-CoV-2.