Methods
This prospective national observational study targeted centers for pediatric pulmonology from all regions of the Czech Republic. From January to June 2021, 11 pediatric pulmonologists enrolled all children aged 2 to 18 years with persistent respiratory symptoms after COVID-19 referred by pediatricians from inpatient or outpatient settings. Inclusion criteria were: (1) presence of dyspnea at rest or on exertion, cough, or chest pain twelve or more weeks after infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2); and (2) documentation of preceding SARS-CoV-2 infection by positive PCR test or detection of significant elevation of antibodies; and (3) absence of any pre-existing chronic respiratory disease. We applied a standardized protocol to evaluate structural and functional anomalies and exclude alternative diagnoses. Initially, medical history, physical examination, lung function testing comprising spirometry, fraction of exhaled nitric oxide (FeNO), diffusing capacity (DLCO), and 6-minute walk test (6MWT), plain chest radiograph, and blood tests were performed in all enrolled children. Laboratory tests comprised blood count, basic biochemistry and allergy panel, D-dimer levels, and SARS-CoV-2 antibodies. In children with abnormal results of the initial panel, we considered individually an extended spectrum of investigative methods: chest ultrasound, spiral chest CT scan with high-resolution reconstruction, CT-pulmonary angiograms, ventilation/perfusion (VP) lung scan. For all enrolled subjects, we scheduled at least two outpatient visits within six months.
We compared numerical variables using One-way ANOVA and categorical variables with Fisher’s exact test. All analyses were performed using IBM SPSS Statistics software version 21. This study was approved by the Ethics Committee with multicentric competence (ID A-21-01).