Comparison of different nucleic acid extraction methods for determining the SARS-CoV-2 nucleic acid detection capability of GENECUBE^® Model C

Abstract

Purpose: Nucleic acid amplification assays for SARS-CoV-2 have been developed rapidly. Our laboratory has been testing for SARS-CoV-2 with Xpert Xpress using nasopharyngeal swab samples. However, the clinical staff requested that saliva samples be tested to prevent secondary infections of the medical staff. Therefore, we introduced GENECUBE^® Model C and GENECUBE^® HQ SARS-CoV-2. We evaluated the heat extraction and magLEAD methods. Methods: ① We prepared a dilution series with AccuPlex and evaluated the results of the two detection methods. ② We added saliva to AccuPlex to prepare a dilution series and examined the effects of the inhibitors on the two methods. ③ We compared the results of the two methods using clinical samples. Results: The LOD of the magLEAD method was 0.25 copies/μL and that of the heat extraction method was 1 copy/μL. From verification ②, the magLEAD method was found to have the same sensitivity as the heat extraction method even when saliva was added, but SARS-CoV-2 could not be detected by the heat extraction method. When verifying the illness days and fluorescence values of 40 clinical samples, the heat extraction method had a significant difference between 1–3 illness days and 4 illness days (p < 0.05). The magLEAD method had no significant difference between them. Conclusion: When using saliva samples, it seems necessary to consider the effects of inhibitors.