ABSTRACT

The testing of saliva samples for severe acute respiratory syndrome coronaviurs 2 (SARS-CoV-2) RNA has become a useful and common method to diagnose coronavirus disease 2019 (Covid-19). We developed a method to collect serial saliva samples on ordinary white printer paper, which can be subsequently analyzed for the presence of SARS-CoV-2 RNA using established polymerase chain reaction (PCR) procedures. The collection systems consisted of a biological diary – a CoronaCal™ – where subjects dab their saliva onto ovals printed onto ordinary paper. The dried samples are covered with a sticker that includes a symptom check-list. Each sheet of letter paper can accommodate up to 30 serial samples. In a pilot study ten subjects used CoronaCals for durations of nine to 66 days. SARS-CoV-2 RNA was detected in CoronaCals from nine of nine people with either Covid-19 symptoms or exposure to someone with Covid-19, and in zero of one asymptomatic person. The CoronaCals were stored for up to 70 days at room temperature before analysis suggesting that SARS-CoV-2 RNA is stable once dried onto paper. Interestingly, the temporal pattern of symptoms was not well correlated with SARS-CoV-2 RNA in serial daily collections for up to 66 days. We conclude that sampling of saliva on simple paper using CoronaCal® may provide a useful and scalable method to study the natural history and epidemiology of Covid-19.