Clinical and functional features of postinfectious airway reactivity formation in children

Introduction. Recurrent respiratory infections in children can present with a wide range of clinical manifestations and may lead to long-term consequences that require further investigation. Aim. To determine the clinical and functional characteristics of the post-infectious reactivity of the airways in children. Materials and methods. The study involved 103 children (38 girls and 65 boys) who had suffered from an acute respiratory infection. The average age of the children was 12.2 ± 0.34 years; height 144.3 ± 1.88 cm, weight 38.0 ± 1.63 kg. A comprehensive diagnostic assessment was conducted, including a questionnaire based on the expanded Asthma Predictive Index (API), collection of biological material from the oropharynx and nasopharynx to detect respiratory RNA and DNA viruses, and collection of peripheral blood to determine specific antibodies of classes M and G to atypical pathogens using enzyme-linked immunosorbent assay (ELISA). The following tests were performed: spirometry (FVC (forced vital capacity), FEV₁ (forced expiratory volume in the first second), FEV₁/FVC ratio, PEFR (peak expiratory flow rate), MEF₅₀ (maximum expiratory flow at the moment of exhaling the first 50% of FVC), MEF₇₅ (maximum expiratory flow at the moment of exhaling the first 75% of FVC), and MEF_25-75 (mean expiratory flow between 25% and 75% of FVC)) with an inhalation bronchodilator test using a short-acting β₂-agonist (salbutamol), as well as a bronchial provocation test with ultrasonic inhalation of distilled water (IDW). Results. The first group included 53 children with altered airway reactivity to the IDW test (ΔFEV_{1 IDW} -5.6 [-13.0; 6.5] %), while the second group consisted of 38 children who did not react to the IDW test (ΔFEV_{1 IDW} -2.9 [-6.0; 1.6] %). Children in the first group had lower spirometric parameters compared to the second group: FEV₁/FVC was 96.0 [92.0; 102.0] and 101.0 [94.0; 104.0] % (p=0.042); and MEF_25-75 was 68.0 [52.0; 88.0] and 80.0 [64.0; 95.0] % (p = 0.029), respectively. When analyzing respiratory pathogens, the first group showed a higher frequency of specific antibodies to M. pneumoniae at 42% compared to 18% in the second group (χ²=4.423; p<0.05). Additionally, in the first group, 28% of cases showed combined (mixed) infection with 2-4 pathogens simultaneously, compared to 8% in the second group (χ²=4.594; p<0.05). Correlation analysis indicated that a high level of IgM antibodies to M. pneumoniae corresponded to a more pronounced response of the small airways to bronchoprovocation with IDW (ΔMEF_{25-75 IDW}) (ρ = -0.63; p=0.01). Conclusion. The study confirms the significant impact of respiratory infections on airway reactivity in children, manifested by decreased spirometric parameters, an increased frequency of pathogen-specific antibodies, and their association with bronchial response to osmotic stimuli. The results of our study highlight the importance of early diagnosis of post-infectious airway reactivity in children.

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