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Risk Factors Associated With Persistent Airflow Limitation in Severe or Difficult-to-Treat Asthma^*

Insights From the TENOR Study

^* From Genentech, Inc. (Drs. Lee and Haselkorn), South San Francisco, CA; University of Virginia Health Systems (Dr. Borish), Charlottesville, VA; ICON Clinical Research (Mr. Rasouliyan), San Francisco, CA; Capital Allergy and Respiratory Disease Center (Dr. Chipps), Sacramento, CA; and University of Pittsburgh (Dr. Wenzel), Pittsburgh, PA.

Correspondence to: June H. Lee, MD, FCCP, Genentech, Inc., 1 DNA Way, MS 453B, South San Francisco, CA 94080; e-mail: lee.june{at}gene.com

Abstract

Background: The Epidemiology and Natural History of Asthma: Outcomes and Treatment Regimens study is among the largest to assess persistent airflow limitation and the first to evaluate a wide range of potential risk factors in high-risk patients with severe or difficult-to-treat asthma. A better understanding is needed regarding factors associated with persistent airway obstruction; this study was performed to determine demographic and clinical characteristics associated with persistent airflow limitation.

Methods: Data from adult patients ( 18 years old) with severe or difficult-to-treat asthma were evaluated. Patients with COPD, obesity with a restrictive respiratory pattern, or a 30 pack-year history of smoking were excluded. Patients with persistent airflow limitation (postbronchodilator FEV₁/FVC ratio 70% at two annual consecutive visits) and normal postbronchodilator FEV₁/FVC ratio (75 to 85%) were compared. Multivariate analysis identified factors independently associated with persistent airflow limitation.

Results: Of 1,017 patients, 612 patients (60%) showed evidence of persistent airflow limitation. Risk factors were as follows: older age (odds ratio [OR] per 10 years, 1.4; 95% confidence interval [CI], 1.3 to 1.6); male gender (OR, 4.5; 95% CI, 2.3 to 8.5); black ethnicity (OR, 2.2; 95% CI, 1.3 to 3.8); current or past smoking (OR, 3.9; 95% CI, 1.8 to 8.6; and OR, 1.6; 95% CI, 1.2 to 2.3, respectively); aspirin sensitivity (OR, 1.5; 95% CI, 1.0 to 2.4); and longer asthma duration (OR per 10 years, 1.6; 95% CI, 1.4 to 1.8). Protective factors were Hispanic ethnicity, higher education, family history of atopic dermatitis, pet(s) in the home, and dust sensitivity.

Conclusions: Persistent airflow limitation is prevalent in patients with severe or difficult-to-treat asthma and is associated with identifiable clinical and demographic characteristics.

Key Words: airway remodeling • difficult-to-treat asthma • irreversible airway obstruction • persistent airflow limitation • severe asthma