Literature Search strategy and Study selection
Relevant databases including Medline, Web of sciences, Embase and Scopus were searched comprehensively to assess literature up to 30 December 2022 in English language. The search terms were including “COVID-19 or corona virus 2019” or “SARS-CoV-2” AND (”pulmonary function” OR ”pulmonary diseases” OR “lung problem”) AND ”children” and ”pediatrics”. They were used separately or/and in combinations to obtain the eligible documents. The references of eligible articles were searched manually to find additional relevant papers. This study was conducted in adherence to the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) statement (10). The current study was based on published articles. Therefore, consent form was not needed. Two researchers (EB and NM) independently reviewed titles and abstracts of all studies to identify relevant articles. Articles were including according to following criteria: (1) English language, longitudinal or cross-sectional studies evaluating the pulmonary function and clinical symptoms of children after COVID 19 infection (2) spirometry parameters have been measured (3) the study population were pediatrics. Case reports, case series, letter to editors, unpublished reports, duplications and laboratory studies were excluded. In duplicate articles, the recent and more informative one was included. Included articles were assessed using Newcastle-Ottawa Quality Assessment Scale (NOS) for cohort and cross-sectional studies (11) if a study obtained five stars it was considered as good quality.