Patients and Methods Study Design This retrospective observational study was conducted on COVID-19 patients (positive polymerase chain reaction [PCR] results via nasopharyngeal swab) between June 1 and mid July 2020. Patients were recruited from Kasr Al-Aini School of Medicine, Cairo University Hospitals. We included all adult patients (18 −75 years) suffering from mild or moderate COVID-19 infection according to World Health Organization (WHO) criteria for the clinical management of COVID-19. 11 Patients were excluded if they had severe COVID-19 disease, were hospitalized, or had unavailable nasopharyngeal swab results. According to WHO classification, COVID-19 infection was categorized into mild, moderate or severe infection. Mild COVID-19 defines as respiratory symptoms without evidence of pneumonia or hypoxia, while moderate or severe infection defined as presence of clinical and radiological evidence of pneumonia. In moderate cases, SpO2 ≥90% on room air while one of the following was required to define the severe cases: respiratory rate >30 breaths/min or SpO2