Fast SARS-CoV-2 detection by RT-qPCR in preheated nasopharyngeal swab samples

Highlights • High-throughput screening of SARS-CoV-2 by RT-qPCR without previous RNA extraction. • Heated nasopharyngeal swab transport medium as template in the RT-qPCR test. • Fast and safety management of SARS-CoV-2 samples in the diagnostic process.
Objectives The gold-standard COVID-19 diagnosis relies on detecting SARS-CoV-2 using RNA purification and one-step retrotranscription and quantitative PCR (RT-qPCR). Based on the urgent need for high-throughput screening, we tested the performance of three alternative, simple and affordable protocols to rapidly detect SARS-CoV-2, bypassing the long and tedious RNA extraction step and reducing the time to viral detection. Methods We evaluated three methods based on direct nasopharyngeal swab viral transmission medium (VTM) heating before the RT-qPCR: a) direct without additives; b) in a formamide-EDTA (FAE) buffer, c) in a RNAsnapTM buffer. Results Although with a delay in cycle threshold compared to the gold-standard, we found consistent results in nasopharyngeal swab samples that were subject to a direct 70°C incubation for 10 min. Conclusions Our findings provide valuable options to overcome any supply chain issue and help to increase the throughput of diagnostic tests, thereby complementing standard diagnosis.