INTRODUCTION
Asthma is a heterogeneous disease that affects both children and adults, with children prevalence that ranges from 4% to 30% in Latin America1. Despite little information on the impact of asthma in developing countries, approximately 130,000 asthma-related hospitalizations and a rate of 5 deaths/day were estimated in Brazil in 20131.
The clinical presentation is characterized by common symptoms such as cough and wheezing, and physiologically with varying degrees of airflow limitation. Typically, these changes occur in association with airway inflammation and remodeling. In children, the mechanisms involved in wheezing are distinct, and some phenotypes may be established from age at onset, presence of atopy, and triggered by viral infections. Approximately one-third of wheezing children will remain symptomatic in adulthood, and factors such as allergic sensitization and smoking increase the chance of its persistence2.
In recent decades, precision medicine has been used to better characterize asthma phenotypes, thus establishing treatment alternatives for patients with severe refractory asthma, which is the real challenge for pulmonologists. Clustering is based on clinical characteristics associated with complementary research, resulting in phenotypes such as early onset allergic asthma or late onset asthma3. However, within a given phenotype, distinct pathophysiological mechanisms may be involved, even in a group of patients with similar clinical presentation. This last concept brings what is now understood as endotype, meaning knowledge at a more specific cellular and immunological level3.
Sputum cytological analysis is cited as a safe and promising technique that evaluates the cellularity present in the lower airway mucosa and can be classified into four main cellular patterns: eosinophilic, neutrophilic, mixed, and pauci-granulocytic. However, there is some heterogeneity of these patterns among patients and their correlation with clinical progression and inhaled corticosteroid treatment response is still a challenge4.
Thus, the objective of this study was to evaluate the feasibility of sputum cytology in children with asthma by recognizing inflammatory patterns. The secondary objectives were to correlate cytological patterns with clinical, epidemiological, and functional disease variables.