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

Alcoba-Florez, Julia; González-Montelongo, Rafaela; Íñigo-Campos, Antonio; de Artola, Diego García-Martínez; Gil-Campesino, Helena; The Microbiology Technical Support Team; Ciuffreda, Laura; Valenzuela-Fernández, Agustín; Flores, Carlos

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 RNAsnap(TM) 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.