Development and clinical application of loop-mediated isothermal amplification combined with lateral flow assay for rapid diagnosis of SARS-CoV-2

The diagnostic assay leveraging multiple reverse transcription loop-mediated isothermal amplification (RT-LAMP) could meet the requirements for rapid nucleic acid detection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2).

The devised assay merged the lateral flow assay with the RT-LAMP technology and designed specific primers for the simultaneous detection of the target and human-derived internal reference genes within a single reaction. An inquiry into the assay's limit of detection (LOD), sensitivity, and specificity was carried out. The effectiveness of this assay was validated using 498 clinical specimens.

This LOD of the assay was determined to be 500 copies/mL, and there was no observed cross-reaction with other respiratory pathogens. The detection results derived from clinical specimens showed substantial concordance with those from real-time reverse transcription-polymerase chain reaction (RT-qPCR) (Cohen's kappa, 0.876; 95% CI: 0.833-0.919; p<0.005). The diagnostic sensitivity and specificity were 87.1% and 100%, respectively.

The RT-LAMP assay, paired with a straightforward and disposable lateral immunochromatographic strip, achieves visual detection of dual targets for SARS-CoV-2 immediatly. Moreover, the entire procedure abstains from nucleic acids extraction. The samples are lysed at room temperature and subsequently proceed directly to the RT-LAMP reaction, which can be executed within 30 minutes at a constant temperature of 60-65°C. Then, the RT-LAMP amplification products are visualized using colloidal gold test strips.

This study was registered at the Chinese Clinical Trial Registry (Registration number: ChiCTR2200060495, Date of registration 2022-06-03).