Study design and participants
This is a single-centered, retrospective study on a group of SARS-CoV-2 infected medical staff at Wuhan Union Hospital, one of the hospitals treating patients with COVID-19 at the earliest time. Diagnosis of cases with SARS-Cov-2 infection conforms to the WHO interim guidance [7]. Details regarding laboratory confirmation protocol for SARS-CoV-2 were described by previous studies [1, 21]. Throat-swab specimens were screened for SARS-CoV-2 and other respiratory viruses (influenza, respiratory syncytial virus, etc.) by real-time RT-PCR assays. This study only considered medical staff that are in service. A total 101 medical staff, which were confirmed by SARS-CoV-2 real-time RT-PCR test on respiratory secretions collected by throat swab and undergone serial chest CT scans following their admission to isolation wards of Union Hospital between 16 Jan and 25 Feb, 2020 were included.
Data collection
The epidemiological data, medical and nursing records, laboratory examinations, chest computed tomography (CT) of all patients were reviewed and abstracted with concerted efforts of experienced clinicians. Data were collected at the time of symptoms onset, presentation for medical advice and in-patient admission. The clinicians who had experience of treating patients with confirmed SARS-Cov-2 infection reviewed and collected the medical records of patients, and preliminarily collated the data. The clinical data were extracted through a standardized form for case report as previously described [23]. Epidemiological data, including exposure histories before symptoms onset (whether there is a history of exposure to the Huanan Seafood Wholesale Market, or wildlife), and close contact with laboratory-confirmed or suspected cases of COVID-19 in a work environment (fever clinics, or isolation wards), specimens (pharyngeal swab, blood, sputum specimens, etc.) or family members with COVID-19 were collected. Also, information about preventive medication among medical staff was collected. In order to compare the difference in temporal distributions of diagnosis between the medical staff and all the confirmed cases of COVID-19 in Wuhan, daily case counts in Wuhan from 1 Dec 2019 to 25 Feb 2020 were collected from reference [1] and official website of the Health Commission of Hubei Province.
We have also collected the data on demographics, clinical manifestations, laboratory examinations and radiological studies. These included age, sex, occupation (doctor, or nurse), body mass index (BMI ≥24, or <24 kg/m2), current smoking status (yes, or no), disease severity (non-severe, or severe), date of symptom onset, diagnosis and hospital admission, symptoms before hospital admission (fever, cough, fatigue, sore throat, myalgia, sputum production, difficulty breathing or chest tightness, chill, loss of appetite, diarrhea, and chest pain), coexisting conditions (e.g. hypertension, diabetes, etc.), laboratory testing indicators on admission (leucocyte count, lymphocyte count, platelet count, D-dimer, creatinine, creatine kinase, lactose dehydrogenase, alanine aminotransferase, aspartate aminotransferase, hemoglobin, ferritin, C-reactive protein, Amyloid A, total bilirubin, procalcitonin, erythrocyte sedimentation rate, interleukin-6 (IL-6) and lymphocyte subsets, etc.), radiologic assessments of chest CT (lung involvement, lung lobe involvement, predominant CT changes, predominant distribution of opacities, etc.), treatment measures (antibiotics agents, antiviral agents, traditional Chinese medicine, immune globulin, thymosin, corticosteroids and oxygen therapy), and complications (e.g. pneumonia, acute respiratory distress syndrome, acute cardiac injury, acute kidney injury, shock, etc.). All CT images were analyzed by two radiologists (J.L. and F.Y., who had 5 and 21 years of experience in thoracic radiology, respectively) utilizing the institutional digital database system without access to clinical and laboratory findings. Images were reviewed independently, and final decisions were reached by discussion and consensus. We estimated the time interval from symptom onset to diagnosis and admission with maximum information available - that is, all the exact date of initial symptoms provided by the patients. Then the aggregated data was sent to data analysis group. Prior to statistical analysis, the aggregated data were cross - checked by group members to guarantee the correctness and completeness of data.
Outcomes
The clinical outcomes and prognosis were continuously observed up to Mar 20, 2020. The primary end point was discharge, needed to meet the following three conditions [24]: (1) body temperature return to normal for more than 3 days and respiratory symptoms improvement; (2) improvement of lung involvement demonstrated by chest CT; (3) two consecutive negative RT-RCR tests, with sampling interval of more than 1 day. Secondary outcomes consisted of hospital discharge rate
Statistical analysis
This study devoted to report epidemiological, clinical characteristics and prognosis of medical staff confirmed with COVID-19. Continuous variables were checked for distribution normality by means of the Kolmogorov-Smirnov test, following which they were summarized as either means with standard deviations (SD) or medians with interquartile ranges (IQR) as appropriate Histograms of distribution of diagnosis date for the confirmed cases in Wuhan and the included medical staff were generated to show epidemic trends. We then estimated the distributions of durations from symptoms onset to diagnosis, symptoms onset to admission, and diagnosis to admission, respectively. Kaplan-Meier method was applied to estimate the change in hospital discharge rate. The proportional hazard Cox regression model was utilized to ascertain potential factors associated with discharge. Univariate models with a single variable once at a time were first fitted. The statistically significant risk factors as well as age and sex were, then, would be considered and selected into a final multivariate Cox regression model. The hazards ratios (HRs) along with the 95% confidence intervals (95% CIs) were calculated.
Statistical tests were two-sided with significance set at α less than 0.05. We performed all data analyses by R software version 3.6.2 (R Foundation for Statistical Computing).