Diagnostic accuracy of LAMP versus PCR over the course of SARS-CoV-2 infection

Inaba, Masato; Higashimoto, Yuki; Toyama, Yoko; Horiguchi, Tomoya; Hibino, Masaya; Iwata, Mitsunaga; Imaizumi, Kazuyoshi; Doi, Yohei

OBJECTIVE: Reverse transcription loop-mediated isothermal amplification (RT-LAMP) has been validated for diagnosis of several viral infections. However, its diagnostic accuracy in detecting SARS-CoV-2 in real-life clinical settings remains unclear. The aim of this study was to determine the diagnostic sensitivity and specificity of RT-LAMP compared to reverse transcription-quantitative polymerase chain reaction (RT-qPCR) over the disease course of COVID-19. METHODS: A total of 124 nasopharyngeal swab samples obtained from 24 COVID-19 patients were tested by RT-LAMP and RT-qPCR. Sensitivities and specificities of RT-LAMP compared with RT-qPCR were analyzed as a function of time from onset. RESULTS: Up to the 9th day after onset, the RT-LAMP had positivity of 92.8%, and the sensitivity and specificity compared with RT-qPCR was 100%. After the 10th day of onset, however, the positivity of RT-LAMP decreased to less than 25%, and concordance of positivity between the two methods was below 60%. The limit of detection of RT-LAMP was 6.7 copies/reaction. CONCLUSIONS: Until the 9th day after the onset of symptoms, RT-LAMP had the same diagnostic accuracy as RT-qPCR. These finding suggest that RT-LAMP can be used as a diagnostic tool for COVID-19 as an alternative to RT-qPCR in the acute symptomatic phase of COVID-19.