The Risk Factors and Clinical Course of Asthma
with Fixed Airflow Limitation
Chaicharn Pothirat MD, FCCP*, Warawut Chaiwong BS*, Chalerm Liwsrisakun MD*, Chaiwat Bumroongkit MD*,
Athavudh Deesomchok MD*, Theerakorn Theerakittikul MD*, Atikun Limsukon MD*, Nittaya Phetsuk BS*
Affiliation :
* Division of Pulmonary, Critical Care and Allergy, Department of Internal Medicine, Faculty of Medicine,
Chiang Mai University, Chiang Mai, Thailand
Objective : To identify risk factors and clinical course of asthma with fixed airflow limitation.
Material and Method: A retrospective case-control study of asthma patients was conducted over a 15-month period. Asthma
with fixed airflow limitation patients were defined as chronic asthmatics who had both post-bronchodilator (BD) and
on-treatment ratio of forced expiratory in first second (FEV1)/forced vital capacity (FVC) persistently less than 0.7, whereas
usual chronic asthma patients had post-BD and/or on-treatment ratio of FEV1/FVC more than 0.7. Serial asthma control
tests (ACT), medication used, exacerbations were assessed. The risk factors were analyzed using logistic regression. Clinical
characteristics between groups were compared using Student’s t-test and Fisher’s exact test.
Results : One hundred twenty from 142 eligible subjects were enrolled. They had asthma with fixed airflow limitation
(n = 40) and usual chronic asthma (n = 80). Potential risk factors of asthma with fixed airflow limitation included early
disease onset (age <15 years) [(adjusted odd ratio (OR) = 3.9, 95% confidence interval (CI) 1.9-8.3)] with longer disease
duration (adjusted OR = 8.4, 95% CI 4.6-15.4 for >30 years). Asthma with fixed airflow limitation patients had lower ACT
scores (p<0.001), lower level of asthma control (p<0.001), required more asthma medications (p = 0.002), and higher rates
of hospitalization (p = 0.001) than usual chronic asthma.
Conclusion : The potential risk factors of asthma with fixed airflow limitation were earlier disease onset and longer disease
duration. They had poorer asthma control, more medications needed, and higher rates of exacerbation than usual chronic
asthma.
Keywords : Asthma, Risk factor, Clinical, Airflow, Limitation
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