Study design, setting, and participants
This retrospective cross sectional study was carried out in Masih Daneshvari hospital, a respiratory center dedicated for COVID-19 patients in Tehran, Iran. COVID-19 patients admitted to the hospital from March 12-26, 2020 were enrolled to the study. COVID-19 cases were confirmed by polymerase chain reaction (PCR) test according to WHO case definition [1]. The study protocol was approved by ethical review board of national research institute of tuberculosis and lung diseases. Written informed consent by the patients was waived due to the retrospective nature of the investigation.