Data extraction and analysis
All studies that met the above-mentioned criteria were carefully
analyzed and strictly reviewed. We collected relevant clinical
information including the population data (e.g. age, gender), number of
patients in the studies, and documented clinical manifestations.
Full-text versions of relevant articles were reviewed, and clinical
characteristics were extracted. The Newcastle-Ottawa quality assessment
scale (NOS) was used to evaluate the quality of included studies12. A scale ranges from 0 to 9, with higher points
indicating higher quality was applied. The two authors (WJ and XG) used
a unified data table to extract data independently, and resolved
controversial issues through further discussion. We define severe
COVID-19 pneumonia as the disease status that requires intensive care
unit (ICU) admission with respiratory/circulatory support10,11,13,14, which is in align with the guideline from
the World Health Organization (WHO). We compared the clinical
characteristics of severe and non-severe COVID-19 pneumonia, followed by
a meta-analysis using three high quality China-based studies.