Clinical COVID-19 diagnostic methods: comparison of reverse transcription loop-mediated isothermal amplification (RT-LAMP) and quantitative RT-PCR (qRT-PCR)

Kitajima, Heita; Tamura, Yoshitaka; Yoshida, Hiroko; Kinoshita, Hitomi; Katsuta, Hiroki; Matsui, Chika; Matsushita, Akane; Arai, Tsuyoshi; Hashimoto, Shoji; Iuchi, Atsuhiko; Hirashima, Tomonori; Morishita, Hiroshi; Matsuoka, Hiroto; Tanaka, Toshio; Nagai, Takayuki

BACKGROUND: The coronavirus disease 2019 (COVID-19) pandemic is a major public health concern. Accurate and rapid diagnosis of COVID-19 is critical for disease control. Reverse transcription loop-mediated isothermal amplification (RT-LAMP) is a nucleic acid amplification assay similar to reverse transcription-polymerase chain reaction (RT-PCR), the former being a simple, low cost, and rapid method. OBJECTIVES: This study aimed to compare the RT-LAMP assay with RT-PCR using the Loopamp(TM) SARS-CoV-2 Detection Kit. STUDY DESIGN: One hundred and fifty-one nasopharyngeal swab and 88 sputum samples obtained from individuals with suspected or confirmed COVID-19 were examined. RESULTS: RT-LAMP had high specificity (98.5% (95% CI: 96.9–100%)), sensitivity (87.0% (95% CI: 82.8–91.3%)), positive predictive value (97.9% (95% CI: 96.1–99.7%)), negative predictive value (90.2% (95% CI: 86.4–94.0%)), and concordance rate (93.3% (95% CI: 90.1–96.5%)). Nasopharyngeal and sputum samples positive in RT-LAMP contained as few as 10.2 and 23.4 copies per 10 μL, respectively. RT-LAMP showed similar performance to RT-PCR for samples with cycle threshold value below 36. CONCLUSIONS: These results indicate that RT-LAMP is a highly reliable and at least equivalent to RT-PCR in utility, and potentially applicable in settings that are more diverse as a point-of-care tool.