Epidemiological clinical features
The demographic and clinical characteristics of the patients are shown in Table 1. 275 patients with laboratory-confirmed COVID-19 were enrolled in this study, including 53(19.3%) imported cases and 222(80.7%) non-imported cases. Among them, 133 were male and 142 were female, with age ranging from 10 to 86 years and an average age of 47.4 years. The proportion of males patients in the imported group was higher than that in the non-imported group (62.3% vs. 44.6%, p= 0.015). The age distribution in the imported and non-imported groups were similar (47.2±14.4 vs. 47.5±16.8, p=0.101). In total, 62 of the 275 patients (22.6%) had at least one coexisting illness (e.g., hypertension or coronary heart disease). Except that non-imported group had a higher proportion of coronary heart disease of 14.4% (32/222) than that in the imported group (1.9%, 1/53, p=0.011), there was no significant difference between these two groups.
In terms of clinical classification, 13 (24.5%) patients were severe type including 6 (11.3%) critically ill cases in the imported group. In the non-imported group, 50 (22.5%) patients were severe type including 22(9.9%) critically ill cases, according to the Chinese clinical guidance for COVID-19 pneumonia diagnosis and treatment (7th edition)[11]. No statistical difference was observed in the proportion of severe or critical illness between the two groups (p=0.523). The median incubation period was eight days in the non-imported group and six days in the imported group, both were longer than four days reported previously[14, 15]. Although the incubation period of the non-imported group was slightly longer than that of the imported group, there was no statistical difference between the two groups (p=0.334).The median time from symptoms onset to hospital admission are 4 days in both imported and non-imported groups.
The most common symptoms at illness onset in the imported group were cough and fever (both were 58.5%), fatigue and sore throat (both were 20.8%), diarrhea (13.2%) and headache (11.3%). The most common symptoms in the non-imported group were cough (54.1%), fever (36%), and fatigue (12.7%). When the two groups were compared, the proportion of asymptomatic patients in the non-imported group was significantly higher than that in the imported group (18.9% vs. 3.8%, p=0.016), and the proportions of symptoms of fever, sore throat, hemoptysis and diarrhea were all lower than those in the imported group (p≤0.048).
Radiologic features
Table 2 shows the radiologic and laboratory findings. Of 218 computer tomography (CT) scans that were performed at the time of admission, 78.9 % revealed abnormal results including ground-glass opacity, local patchy shadowing, bilateral patchy shadowing and interstitial abnormalities. The most common patterns on chest CT in both imported and non-imported cases were bilateral patchy shadowing and local patchy shadowing. The abnormal patterns of two or more types were 33.3% in the imported group and 37.4% in the non-imported group. In general, there was no statistical difference in the proportion of the imported group and the non-imported group for each image performance (p≥ 0.175).
As to asymptomatic patients, 33.3% had no abnormal chest CT images. The most common patterns on chest CT were ground-glass opacity (20 %) and local patchy shadowing (15.6%). The proportion of bilateral patchy shadowing and interstitial change was 6.7% and 4.4%, respectively. 22.2% of the patients had two or more of the above abnormal images on chest CT. When compared with the symptomatic patients, the ground-glass opacity was more common in asymptomatic patients (20% vs. 5.2%, p=0.004), while the proportions of bilateral patchy shadowing (6.7% vs. 22.5%) and multiple manifestations (22.2% vs. 39.9%) were lower (p≤0.02).
Laboratory findings
Lymphocytopenia was presented in 59.6% of the enrolled patients, and the proportion of lymphocytopenia in the imported group and the non-imported group was 69.8% and 57.2%, respectively. The difference was not statistically significant (p=0.093). However, the absolute value of lymphocyte count in the imported group was significantly lower than that in the non-imported group (1.1×109/L [IQR 0.9-1.6] vs. 1.5×109 /L [IQR 1.0-1.8], p=0.018). 35.6% of the patients had increased C-reactive protein (CRP). The proportion of increased C-reactive protein in the imported group was 49.1%, which is higher than that (32.4%) in the non-imported group (p=0.02). The neutrophil-to-lymphocyte ratio (NLR) of the imported group was 2.6 [IQR 2.0-3.6], which is higher than that of the non-imported group (2.3 [IQR 1.5-3.6]) (p=0.0237). In total, 65.5% of the patients had elevated levels of activated partial thromboplastin time (APTT). 34.2% had elevated erythrocyte sedimentation rate (ESR), 24% had elevated Lactate dehydrogenase (LDH), and 23.3% had elevated procalcitonin (PCT). Less common were elevated levels of D-dimer, alanine aminotransferase (ALT), aspartate aminotransferase (AST), prothrombin time (PT) and creatine kinase (CK). There was no statistical difference between the two groups in all of these indicators (p≥0.065).
Furthermore, we investigated the CD4+ and CD8+ T cells between imported and non-imported groups. We found that the proportion of CD4+ T cells reduction in the imported group was higher than that in the non-imported group (70% vs. 44.6%, p=0.043), while the count of CD4+ T cells was not different between the imported group and the non-imported group (375/μL [IQR 274-509.5] vs. 509 /μL[IQR 281-612], p=0.15), although the imported group indeed had a lower median value. The difference in proportion of CD8+ T reduction or the count of CD8+ T cells between the imported and non-imported groups was not statistically significantly different (p≥0.275).
As to asymptomatic and symptomatic patients, higher lymphocyte count as well as CD4+ T and CD8+ T lymphocyte was found in asymptomatic patients compared with symptomatic patients (p≤0.029).
Moreover, when compared with imported group, asymptomatic group showed higher lymphocyte count (1.6×109/L vs. 1.1×109 /L, p<0.001) and CD4+ T cells(567 vs.375, p=0.029), while the symptomatic group showed no difference in lymphocyte count, CD4+ or CD8+ T cells (p ≥ 0.0894).
Treatment and clinical outcomes
All patients received antiviral therapy for 3-12 days, including oseltamivir, opinavir and ritonavir tablets, arbidol or interferon alpha inhalation. 31.2% patients received antibiotic treatment. The duration of antibiotic treatment was 3-15 days (median 6 days [IQR 4–9]). 20.7% patients were also treated with systemic glucocorticoids. 20.4% patients received non-invasive ventilator mechanical ventilation for 3-20 days (median 8 days [IQR 6–18]). 3 (1.1%) patients used an invasive ventilator to assist ventilation for 3-20 days (median 17 [12–19]). Overall, there was no significant difference between the imported group and the non-imported group in all of these indicators.
As of March 1, 2020, all of the 53 patients in the imported group were discharged from the hospital, while 188 of the 222 patients in the non-imported group were discharged, and no patients had died. The median duration of hospitalization was 17 days (IQR 11.8-24.3) in the imported cases and 15 days (IQR 12-20) in the non-imported cases. There was no statistical difference in the two groups. Median duration of viral shedding was 20 days (IQR 13.8-27) in the imported cases, which was longer than that of 18 days in the non-imported cases (IQR 12-23) (p = 0.0416).
Furthermore, the median duration of viral shedding in symptomatic patients was 20 days, which was longer than that of 13days (p<0.001) in the asymptomatic patients , and the median duration of hospital stay in the symptomatic patients was longer than that in the asymptomatic patients (17 days vs. 14 days,p=0.015).