Fixed airways obstruction among patients with severe asthma: findings from the Singapore General Hospital-Severe Asthma Phenotype Study

Yii, Anthony Chau Ang; Tan, Gan Liang; Tan, Keng Leong; Lapperre, Therese Sophie; Koh, Mariko Siyue

doi:10.1186/1471-2466-14-191

Title

Fixed airways obstruction among patients with severe asthma: findings from the Singapore General Hospital-Severe Asthma Phenotype Study

Author

Yii, Anthony Chau Ang

Tan, Gan Liang

Tan, Keng Leong

Lapperre, Therese Sophie

Koh, Mariko Siyue

Abstract

Background: A subset of severe asthma patients has fixed airways obstruction, which is characterized by incomplete reversibility to bronchodilator challenge. We aimed to elucidate the factors associated with fixed airways obstruction in a cohort of patients with severe asthma in Singapore. Methods: 245 patients from the Singapore General Hospital-Severe Asthma Phenotype Study (SGH-SAPS) were screened. These patients fulfilled World Health Organization criteria for "treatment-resistant severe asthma" and were all on combination of high-dose inhaled corticosteroids and long-acting beta2 agonists. 76 patients had pre- and postbronchodilator lung function tests and were selected for analysis. They were divided into two groups based on postbronchodilator (Post BD) forced expiratory volume in one second, PostBDFEV(1) % predicted: >= 70% (Non-Fixed Obs) and < 70% (Fixed Obs). We compared clinical and demographic parameters between the two groups. Results: Patients in the Fixed Obs group were more frequently past or current smokers and had a higher pack-year smoking history. Overall, pack-year smoking history had a modest negative correlation with PostBDFEV(1) % predicted. Atopy, allergen sensitization (type and numbers), comorbidities, symptoms, health care utilization and medication use did not differ between the two groups. The prebronchodilator FEV1 % predicted, FEV1/FVC and FVC % predicted were significantly lower in the Fixed Obs group. In addition, prebronchodilator FVC % predicted accounted for more variability than FEV1/FVC in predicting PostBDFEV(1)% predicted. Conclusion: Smoking is associated with fixed airways obstruction in patients with treatment-resistant severe asthma in Singapore. Furthermore, our results suggest that both small and large airways obstruction contribute independently to fixed airways obstruction in severe asthma.

Language

English

Source (journal)

BMC pulmonary medicine. - London

Publication

London : 2014

ISSN

1471-2466

DOI

10.1186/1471-2466-14-191

Volume/pages

14 (2014) , p. 1-9