Literature Search
We initially retrieved 1686 articles about COVID-19, 30 of which met the criteria for inclusion in our series (eTable 1). Reasons for exclusion included duplicate reports (n=791), reports not describing clinical characteristics (n=736), and other types of studies such as comments and letters to the editor (n=129) (Figure 1). Both two independent reviewers screened all records. The agreement between reviewers, as determined by weighted kappa, was 0.92 (95% CI:0.88–0.95), indicating excellent interrater reliability[24].
Study Characteristics
All included studies are summarized in detail in eTable 1 (online supporting information). Data were grouped under the following subheadings: author and area, reference, study setting, study quality as reported by STROBE score (between 0 and 4). The most common methodological issues included absent or incomplete definitions of outcome variables or minor inconsistencies in data analyses. Among these studies, there were 21 cross-sectional studies, 9 retrospective studies, and 8 studies included individual patient data of 26 patients[17] [18] [2] [25] [26] [27] [28] [29] (eTable 2). Among all of these studies, 16 were from the Wuhan area; the other 14 studies were from outside the Wuhan area. Study size ranged from 3 to 201 subjects. 16 studies involved less than 50 cases, and 14 studies involved more than 50 cases.
Clinical symptoms
There were 10 frequent symptoms of COVID-19 that were reported in China. The valid pooled incidence rate was calculated for four symptoms, which have the lower heterogeneity, i.e., rhinorrhea 5.1% (95% CI: 3.7-6.8, I2=31.90), diarrhea 11.0% (95% CI: 9.3–12.9, I2=16.58), pharyngalgia 9.4% (95% CI: 7.5-11.7, I2=36.40), headache 9.5% (95% CI: 8.5-11.1, I2=5.7). Notably, 73 patients were found without any symptoms although they were diagnosed by RT-PCR. The pooled incidence rate of patients without obvious symptoms was 4.3% (95% CI: 3.5-5.4, I2=0.00) (Table 1). Among the reported clinical symptoms, significant of heterogeneity was present in the symptoms of fever (I2 = 86.79%, P = 0.000), cough (I2 = 79.51%, P = 0.004), expectoration (I2 = 83.08%, P = 0.000), anhelation (I2 = 83.95%, P = 0.001), muscle pain (I2 = 76.76%, P = 0.000), and fatigue (I2 = 86.69%, P = 0.000). We found no identifiable sources of heterogeneity using subgroup analysis. The results of subgroup analyses according to geographic region and study scale are presented in Table 2.
Blood routine examination
Lymphocytes were below the normal range in 725 patients, the pooled incidence rate of elevated neutrophils was 36.7% (95% CI: 33.8-39.8), and no significant heterogeneity was found (I2 = 28.73%, P = 0.083) (Table 1). There were 327 patients with neutrophils above the normal range, and evidence of heterogeneity and publication bias was present among these findings (I2 = 80.71%, P = 0.01). White blood cells were below the normal range in 318 patients (I2 = 73.77, P = 0.000) and above the normal range in 335 patients (I2 =80.01, P = 0.000). We found no identifiable sources of heterogeneity using subgroup analysis (Table 2).
CT imaging
The chest CT images of COVID-19 patients were reported in different ways. By reviewing the literature, we found three common manifestations, as follows: (1) bilateral mottling or ground-glass opacity, (2) unilateral mottling or ground-glass opacity, and (3) crazy-paving pattern. Among the studies, 1477 patients showed bilateral mottling or ground-glass opacity, 312 patients showed unilateral mottling or ground-glass opacity, and 150 patients showed a crazy-paving pattern (7.7%, 95% CI: 4.4-12.9, I2=35.64). Evidence of heterogeneity was present in the bilateral mottling or ground-glass opacity (I2 = 80.05%, P = 0.000), and in the unilateral mottling or ground-glass opacity (I2 = 73.15%, P = 0.000). We found no identifiable sources of heterogeneity using subgroup analysis. Furthermore, there were 44 patients with normal CT presentations during the period of COVID-19. Significant heterogeneity was observed in this group (I2 = 56.92%, P = 0.000). However, in subgroup analysis, heterogeneity was decreased (I2 = 24.78%, P = 0.187, egger’s test P = 0.874), which indicated that the heterogeneity may come from the geographic region (Table 2). The pooled incidence rate of normal CT presentations in the Wuhan area and outside Wuhan area was 2.3% (95% CI: 1.4-3.6) and 5.4% (95% CI: 4.4-7.7), respectively (P=0.001) (Table 2, Figures 2, 3).
Oxygen therapy
Nearly all of the patients accepted oxygen therapy. Among these studies, 458 patients accepted mechanical ventilation, and the inhaled oxygen concentration was 35-100%; There was significant heterogeneity in the mechanical ventilation group (I2 = 72.45%, P = 0.000) (Table 1). We cannot identify sources of heterogeneity by subgroup analysis (Table 2). Additionally, 28 patients were treated with extracorporeal membrane oxygenation (ECMO); the pooled incidence was 2.9% (95% CI: 1.8-4.4, I2=26.77) (Table 1). There was no evidence of heterogeneity or publication bias.
ARDS
Among these studies, 421 patients developed to ARDS. There was significant of heterogeneity (I2 = 77.35%, P = 0.000) (Table 1). In subgroup analysis, heterogeneity was decreased, which indicated that the heterogeneity might come from the geographic region. We found the Wuhan area (34.3%, 95% CI: 30.6-38.1) has a significant higher incidence of ARDS than outside Wuhan areas (15.1%, 95% CI: 12.0-18.8), P=0.000 (Table 2).