SARS-CoV-2 Detection from Clinical Specimens

All self-collected specimens were tested at the Institute of Medical Virology, Goethe University Frankfurt. Dry swabs (nasal swab, tongue swab) were suspended in 2 mL of phosphate-buffered saline (PBS) and incubated for 5 min prior to further processing. Depending on the viscosity in the self-collected specimen and to achieve the required input volume, saliva was diluted up to 1:2.5. The chewed cotton pads with saliva were suspended in 4 mL of PBS, compressed, and incubated for 5 min. Gargle solution was used native, without further dilution. Samples were stored at −80 °C until nucleic acid extraction and PCR-based testing was performed. Specimens were extracted using the QIAsymphony and the DSP virus/pathogen midi kit (both Qiagen GmbH, Hilden, Germany) according to the manufacturers’ protocols. Realtime RT-PCR (rRT-PCR) analysis was performed using the RealStar^® SARS-CoV-2 RT-PCR Kit 1.0 (Altona Diagnostics GmbH, Hamburg, Germany) [17 (link)] on the ABI PRISM^® 7500 Analyser (Applied Biosystems, Waltham, MA, USA) according to the manufacturers´ specifications. Three quantitative comparison samples containing 10⁵, 10⁶, and 10⁷ SARS-CoV-2 (BetaCoV/Munich/ChVir984/2020) RNA copies/mL were used to generate a standard curve and to calculate the viral RNA copies/mL. Equivocal test results were excluded from the analysis of testing sensitivity.