Association between prescribing patterns of anti-asthmatic drugs and clinically uncontrolled asthma: a cross-sectional study

OBJECTIVE: Studies based on prescription data have shown that many asthmatics tend to use large quantities of inhaled beta-2-agonists, suggesting poorly controlled disease. The aim of the present study was to investigate the association between clinically uncontrolled asthma and prescribing patterns of anti-asthmatic drugs with a primary focus on short-acting beta-2-agonists (SABA).

METHODS: In a cross-sectional study 357 subjects, selected by their prescriptions of inhaled beta-2-agonists in Odense Pharmaco-Epidemiological Database, underwent individual clinical assessment including the Asthma Control Questionnaire (ACQ) and spirometry. The associations between uncontrolled asthma (ACQ score ≥ 1.50) and individual anti-asthmatic prescribing were analysed by means of logistic regression.

RESULTS: Clinically uncontrolled asthma was positively associated with SABA use, the association becoming stronger with higher annual quantity of SABA use, odds ratio (OR) 11.1 (95% CI 4.4-28.0) for ≥400 DDD/year. This trend persisted after stratifying for gender, age, and controller treatment. Although subjects using ≥450 DDD/year were all uncontrolled, there was substantial overlap in SABA use between controlled and uncontrolled subjects below this limit. We found no effect modification by age and gender. Use of inhaled corticosteroids protected against uncontrolled asthma, OR 0.51 (95% CI 0.27-0.95).

CONCLUSION: Asthmatics with a high use of SABA frequently have problems with uncontrolled asthma, and users of ICS are protected against uncontrolled asthma. The associations we found were, however, to weak too allow firm conclusions about asthma control for most individual asthma patients.