3.1 Characteristics of the included studies:
The preliminary search reported 1689 articles. Seven hundred thirty-five studies were included after removing duplicates. After considering the title and abstract, 663 articles were eliminated, leaving 72 papers that were regarded as plausible for this analysis. Following review of these studies based on the inclusion and exclusion criteria, 30 articles totaling 81,929 COVID-19 patients were eventually included in this meta-analysis., Table 1 summarizes the baseline characteristics of the included studies.