2.2 Data Collection
The electronic medical records of each patient were extracted and analyzed by four independent researchers with a standardized data collection form. Patients’ demographic and baseline characteristics (including age, sex, exposure history, comorbidities, surgery history and smoking history), symptomatic and radiological characteristics [including signs and symptoms, and chest computed tomography (CT) results], as well as the laboratory findings on admission (including complete blood cells counts and percentages, and biochemical parameters), and follow-up data of laboratory parameters in severe survived and non-survived patients were obtained and analyzed. The clinical outcome of each patient (i.e. non-survived, discharged, or remained in hospital) as of Mar 28th, 2020 (the final follow-up date) and the intervals of symptoms onset (i.e. the day when the symptoms were noticed) to hospital admission for each patient were also recorded.
Information in regards of the disease severity, occurrence of complications (shock, respiratory failure or acute renal failure), co-infection status with other pathogens during the hospital stay was collected. The available chest CT images of each patient were reviewed by a senior radiologist blinded to the clinical data, in order to confirm detailed abnormality of radiological characteristics of these patients. The presence or absence of the three following features was recorded for each patient: 1) ground-glass opacity (GGO); 2) subpleural lesions and pleural effusion; 3) affected pulmonary lobe numbers.
The presence of exposure history was defined as any close contact with patients diagnosed with COVID-19 (for example, familial cluster occurrence or occupational exposure of healthcare professionals) or has visited Huanan wet market since December 2019. Severe COVID-19 was designated, if the patients met one of the following criteria: (a) respiratory distress with respiratory frequency ≥ 30/min; (b) pulse oximeter oxygen saturation ≤ 93% at rest; and (c) oxygenation index (artery partial pressure of oxygen/inspired oxygen fraction, PaO2/FiO2) ≤ 300 mmHg.