Alternative RNA extraction-free techniques for the real-time RT-PCR detection of SARS-CoV-2 in nasopharyngeal swab and sputum samples.

ABSTRACT

Standard diagnoses of SARS-CoV-2 infections are done by RNA extraction and real-time RT-PCR (rRT-PCR). However, the need for RNA extraction complicates testing due to increased processing time, high cost, and limited availability of commercial kits. Therefore, alternative methods for rRT-PCR detection of SARS-CoV-2 without RNA extraction were investigated. Nasopharyngeal and sputum samples were used to compare the sensitivity of three techniques Trizol RNA extraction, thermal shock, and the direct use of samples with an RNase inhibitor. Direct, extraction-free use of primary samples plus the RNase inhibitor produced diagnostic values of 100 % sensitivity and specificity compared to standard protocols, and these findings were validated in a second, independent laboratory.