DISCUSSION
The present study expands the perspectives in the therapeutic follow-up of children with asthma, mainly in reference centers. Few studies have been published on the subject in in children in this age group.
. The sample size was adequate and the success rate was 58%, comparable to that of similar studies, since it is a specific population, reflecting a good applicability of the method to the pediatric population12. In addition, the method proved to be safe. No patient had adverse events or had to interrupt the procedure. Bronchospasm was not observed during the procedure, even in the case of an asthmatic population. Proven safety of the procedure and the incorporation into the routine of the investigation of children with asthma in our center, there was an increase in the number of viable samples, when compared to the beginning of the study execution.
There was a predominance of children with severe asthma in the study population. Justified by the fact that the study was conducted in a tertiary hospital that serves patients of greater complexity and is a reference for primary health care services in the region.
The predominance of the eosinophilic pattern in the sputum pattern (54%) was expected and has already been described in other studies, mainly in children, who frequently present the allergic phenotype. Eosinophils are the main inflammatory cells in the pathogenesis of asthma, especially in atopic patients, who generally have a profile of Th2 cytokines, represented by IL-4, IL-5 and IL-13, blood eosinophilia and increased total IgE 13,14.
Another important finding in this study was the positive correlation between sputum and blood eosinophil counts. Although some studies do not show this correlation, this correspondence is interesting since the collection of peripheral blood is easier and more accessible when compared to sputum induction and could be used to guide and monitor the treatment of childhood asthma. Further studies are needed to clarify this association15,16,17.
The considerable frequency of non-eosinophilic phenotypes (neutrophilic and pauci-granulocytic) is noteworthy in these asthmatic patients (43.5% of the sample).
Sputum neutrophilia is related to severe asthma in adults, resistant to treatment with inhaled corticosteroids and less related to atopy4. In pediatrics, several hypotheses about the presence of neutrophils in sputum have been formulated, including the greater occurrence of viral infections, which are known to generate neutrophilic inflammation. Sputum is not routinely analyzed in children with acute respiratory symptoms, which could elucidate the finding and to avoid bias. Another hypothesis suggested would be that there would be an increase in neutrophils in the bronchial mucosa in response to treatment with corticosteroids inhaled by chemotaxis and inhibition of apoptosis of these cells in sputum 18,19. In view of this, an initial eosinophilic pattern could hypothetically become mixed with treatment with inhaled corticosteroids. In this study, there was no significant difference between sputum cytological profiles and children’s inhalation treatment, but the cross-sectional character of the study is a limitation. In a longitudinal study evaluating treatment-resistant pediatric patients with severe asthma, Eller et al. reported a greater number of eosinophils in the initial induced sputum of patients who obtained better control of asthma, with a tendency to become pauci-granulocytic in the final sample20. The authors showed that the presence of neutrophils was higher in the sputum of children with uncontrolled asthma20. In this study group there was a predominance of the eosinophilic pattern even in children using inhaled corticosteroids as well as children with non-eosinophilic sputum pattern were not all in the uncontrolled asthma group. The follow-up, with serial sputum evaluations of the same patient, may clarify this question.
Allergic comorbidities were prevalent in the studied group, with percentages of rhinitis and atopic dermatitis similar to those of two other studies developed in Brazil21,22,23. Almost all asthmatics evaluated had allergic rhinitis, drawing attention to this frequent association23. This atopic profile was confirmed by a high frequency of total IgE above normal and peripheral eosinophilia in the study population.
Most patients (85%) were sensitized, especially to household dust mites, again confirming the atopic profile of the population and according to data published from other Brazilian cities24,25,26. In the case of children with moderate to severe illness, recommendations to avoid exposure to these allergens should be emphasized at each visit.
Lung function was normal in most patients, despite having clinically moderate or severe asthma, uncontrolled in 43.2% of cases. Previous studies have already pointed out that the findings of spirometry may not be faithfully related to the severity of childhood illness and that clinical parameters are the most useful for conducting treatment in this age group27. However, the role of spirometry in the management of asthma is well established, since it is useful to identify patients at higher risk due to the presence of obstructive ventilation defect and a positive response to bronchodilator28. This response in patients with normal spirometry is an alert to specialists and may represent an objective parameter of uncontrolled disease28. In this study, 22.2% of children had positive responses after using 400 mcg of salbutamol.
This study has some limitations, such as the cross-sectional design, the difficulty in correlating the sputum pattern with other variables, especially with the use of drugs such as inhaled or systemic corticosteroids. The collection of more than one sputum sample from the same patient, at different times, could confirm the predominant pattern and possible interferences of the medication.
In conclusion, this study found a predominance of eosinophilic profile in the sputum of stable asthmatic children, but it also showed that other cytological patterns may be present, especially in a population of severe asthmatics.
The study also proved the viability of sputum induction in children with asthma, representing a safe, effective and tolerant technique that would be valuable in investigating patients who require specialized care, contributing to the perspective of individualization. treatment.