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Development and clinical application of a rapid and sensitive loop-mediated isothermalamplification test for SARS-CoV-2 infection

By Xuejiao Hu, Qianyun Deng, Junmin Li, Jierong Chen, Zixia Wang, Xiqin Zhang, Zhixin Fang, Haijian Li, Yunhu Zhao, Pan Yu, Wenmin Li, Xiaoming Wang, Shan Li, Lei Zhang, Tieying Hou

Posted 23 May 2020
medRxiv DOI: 10.1101/2020.05.20.20108530

Background The outbreak of SARS-CoV-2 urgently requires sensitive and convenient COVID-19 diagnostics to assure the containment and timely treatment of patients. We aimed to develop and validate a novel reverse transcription loop-mediated isothermal amplification (RT-LAMP) assay to detect SARS-CoV-2 in both qualified laboratories and point-of-care settings. Methods Patients with suspected COVID-19 and close contacts between Jan 26 and April 8, 2020, were recruited from two hospitals. Respiratory samples were collected and tested with LAMP and the results were compared with those obtained by RT-qPCR. The inconsistent samples between these two methods were subjected to next-generation sequencing for confirmation. In addition, we tested the RT-LAMP on an asymptomatic COVID-19 carrier and patients with other respiratory viral infections. Results We finally collected a cohort of 129 cases (329 nasopharyngeal swabs) and the independent cohort of 76 patients (152 nasopharyngeal swabs and sputum samples). RT-LAMP was validated to be accurate (overall sensitivity and specificity: 88.89% and 99.00%; positive and negative predictive values: 94.74% and 97.78%) and diagnostically useful (positive and negative likelihood ratios: 88.89 and 0.11). RT-LAMP showed an increased sensitivity (88.89% vs 81.48%) and high consistency (kappa 0.92) compared with RT-qPCR for SARS-CoV-2 screening while requiring only constant temperature heating and visual inspection. The median time required for RT-LAMP was less than 1 h from sample to result. Further analyses indicated that RT-LAMP was feasible for asymptomatic patients and did not cross-react with other respiratory pathogen infections. Conclusion The RT-LAMP assay offers a rapid, sensitive and straightforward detection for SARS-CoV-2 infection, which could aid the expansion of COVID-19 testing in the public domain and hospitals.

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