2.2 Study selection and data extraction
The meta-analysis of the results in original studies conducted on humans that had the following MeSH terms and free words in the title or abstract: ‘COVID-19’ AND ‘ARDs’ or ‘Arthritis, Rheumatoid’ or ‘Lupus Erythematosus, Systemic’ or ‘Sjogren’s Syndrome’ or ‘Antiphospholipid Syndrome’ or ‘Spondylitis, Ankylosing’ or ‘Arthritis, Psoriatic’ or ‘Vasculitis’ or ‘Gout’ or ‘Connective Tissue Diseases’ or ‘Scleroderma, Systemic’.
The meta-analysis excluded studies that were non-original, multiple reports of the same or overlapping data, or conducted without a control group. Single case reports were excluded. As for the clinical outcomes of COVID-19, studies including only hospitalized or dead patients were excluded. In addition, we excluded studies with missing data that could not be obtained even after contacting the authors.
Two investigators independently assessed the studies based on the eligibility criteria; a third investigator resolved disagreements. A data collection sheet was used to record information related to the first author’s name, publication year, study design, study location, numbers of patients diagnosed with COVID-19, type of medications, age, gender, prevalence, and clinical outcomes of COVID-19 were collected. We rated the quality of evidence according to the Grades of Recommendation, Assessment, Development, and Evaluation (GRADE) approach to assess the certainty of evidence obtained from the present meta-analysis. Evidence was graded according to the Newcastle–Ottawa Quality Assessment Scale (NOS). The quality of studies was assessed using Stata 12.0.