Mixed Sputum Granulocyte Longitudinal Impact on Lung Function in the Severe Asthma Research Program

Area of Science:

• Pulmonary Medicine
• Immunology
• Asthma Research

Background:

• Sputum differential cell counts in asthma exhibit variable longitudinal patterns.
• Elevated sputum eosinophils and neutrophils are linked to asthma severity and lung function decline.

Purpose of the Study:

• To investigate the longitudinal stability and variability of sputum granulocytes in severe asthma.
• To determine the association of sputum granulocyte patterns with clinical characteristics and lung function.

Main Methods:

• Utilized the Severe Asthma Research Program III (SARP III) cohort with 3-year longitudinal data.
• Categorized subjects into groups based on predominant sputum eosinophil (<2%, ≥2%) and neutrophil (≥50%) levels or high variability.
• Assessed lung function (FEV1, FEV1/FVC) and healthcare utilization over time.

Main Results:

• Predominantly <2% eosinophils were associated with the highest lung function throughout the study.
• A combination of ≥2% eosinophils and ≥50% neutrophils correlated with the lowest lung function.
• Highly variable eosinophil percentages were linked to increased asthma exacerbations and healthcare use at Year 3.

Conclusions:

• Persistent sputum eosinophilia (≥2%) combined with neutrophilia (≥50%) indicates greater lung function loss in severe asthma.
• Highly variable sputum eosinophil counts are associated with increased healthcare utilization.
• Sputum granulocyte patterns provide valuable prognostic information for severe asthma management.