2.4 Study Quality Assessment:
The quality of the included studies was assessed using nine quality assessment criteria adapted from Littell et al. (24): (1) Was the research problem clearly mentioned? (2) Were the inclusion and exclusion criteria clearly mentioned? (3) Were the subjects in the study representative of the pathological population? (4) Were the principaloutcome of the study clearly mentioned? (5) Was a control group included? (6) Were effect of corticosteroid therapy clearly mentioned (7) Were diagnosis method of COVID-19 clearly defined (8) Was a sample size justification via power analysis provided? (9) Were potential confounders properly controlled in the analysis? Each of the nine criteria was scored on a scale of zero to two, depending on whether the criterion was unmentioned or unmet (0), partially met (1), or completely met (2). The possible total score ranged from zero to 18. The study quality score was used to quantify the strength of existing evidence but was not used in the study selection.