Asthma phenotyping: Correlation between inflammatory phenotype, clinical parameters and associated comorbidities

Introduction: Cluster analysis revealed 5 clinically different clusters of asthma: mild atopic (1), mild to moderate atopic(2), late-onset non-atopic (3), severe atopic (4) and severe with fixed airflow obstruction (5) (Moore et al, 2009). Aim: To link differential cell count and associated comorbidities (BMI, smoking, atopy, reflux, sinusitis and bronchiectasis) to 5 clusters of asthma based on clinical features (baseline FEV1, maximal FEV1 and age of onset). Methods: We retrospectively evaluated clinical records from 140 asthma patients (44% male; 43y ± 14) with induced sputa, recruited from outpatient clinic of the University Hospital Leuven between January 1st 2008 and November 1st 2011 and were free of exacerbation for three months prior to sputum induction. Results: Cluster 1 accounted for 37%, cluster 2 for 26%, cluster 3 for 14% and cluster 4 for 12%. Cluster 5 was too small for further analysis. Cluster 4 as defined by Moore and coworkers is significantly associated with more neutrophils (median: 72%, interquartile: 60-82%); p Conclusion: Severe atopic asthmatics have a predominant neutrophilic airway inflammation. Patients with late-onset non-atopic asthma have the highest rate of reflux. Previously unrecognized bronchiectasis were detected in 9% of patients.