Sampling from Upper And/Or Lower Respiratory Tract When Diagnosing Coronavirus Disease 2019 (COVID-19)? – Results from a Danish Cohort Study

Objectives: We aimed to examine whether symptoms and duration of coronavirus disease 2019 (COVID-19) were associated with the respiratory compartment from which sample material has been found PCR test positive.Methods:We conducted a retrospective cohort study in the Central Denmark Region, from February 28th 2020 to November 2nd 2020. Hospitalised patients who had severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) PCR samples from both the upper and lower respiratory tract within 48 hours and at least one positive test result were included. Results: Of 139 patients, 115 were positive in both samples (83 %), 7 (5%) were positive only in the upper respiratory tract sample, and 17 (12 %) were only positive in the lower respiratory tract sample.Conclusions:The majority of double sampled patients were SARS-CoV-2 PCR positive in both upper and lower respiratory tract (83 %). In our study, 12 % of patients with an infection in the lower respiratory tract would not have been diagnosed with COVID-19 if double sampling or supplemental sampling was not performed. Symptom duration or whether the patient had symptoms corresponding to upper or lower respiratory tract infection could not be used in our study to determine whether double sampling is necessary.