Development of a reverse transcription loop‐mediated isothermal amplification assay with novel quantitative pH biosensor readout method for SARS‐CoV‐2 detection

Reverse transcription loop‐mediated isothermal amplification (RT‐LAMP) is a molecular amplification method that can detect SARS‐CoV‐2 in a shorter time than the current gold‐standard molecular diagnostic reverse transcription‐polymerase chain reaction (RT‐PCR). However, previously developed RT‐LAMP assays have mostly relied on highly subjective visual colorimetric interpretation. In this study, an RT‐LAMP assay was developed with quantitative measurement of reaction pH using a novel portable pH biosensor compared to qualitative colorimetric interpretation and gel electrophoresis, with 57 clinical COVID‐19 samples used for validation of the test. The LoD of the assay is 10³ copies/μL. The highest sensitivity was found in the qualitative methods (93.75%), while the highest specificity and likelihood ratio was found in the pH sensor (87.5% and 6.72). On the sensor measurement, a significant difference (p < 0.0001) was observed between the average pH of the RT‐PCR (+) COVID‐19 (6.15 ± 0.27), while the average pH of the RT‐PCR (−) samples (6.72 ± 0.22). Correlation analysis revealed a strong correlation (r = 0.78, p < 0.0001) between the Ct values obtained from RT‐PCR with the biosensor pH readout. RT‐LAMP with the quantitative pH sensor readout method has the potential to be further developed as an objective molecular assay for rapid and simple detection of SARS‐CoV‐2.