A bronchodilator response (BDR) is not associated with asthma control or symptoms among patients with poorly controlled asthma, regardless of the definition of BDR that is used, according to study findings published in Respiratory Medicine.
Researchers sought to determine the relationship between BDR and asthma control and symptom burden in patients with poorly controlled asthma. Toward that end, the researchers evaluated 4 different BDR definitions in patients with poorly controlled asthma from 3 large clinical trials of the American Lung Association-Airways Clinical Research Centers (ClinicalTrials.gov Identifiers: NCT00442013, NCT00069823, and NCT01052116).
The 4 definitions of BDR were:
- definition 1: forced expiratory volume in the first second (FEV1) or forced vital capacity (FVC) increases by greater than 12% and 200 mL of its baseline value;
- definition 2: FEV1 or FVC increases by more than 10% of its predicted value;
- definition 3: FEV1 increases by more than 8% of its predicted value; and
- definition 4: FEV1 increases by more than 0.78 z-score, or FVC increases by more than 0.64 z-score.
Asthma control was measured with use of the Asthma Control Test or Asthma Control Questionnaire, and the burden of asthma symptoms was measured with the Asthma Symptom Utility Index.
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[T]he findings of this study question the clinical utility of assessing a BDR in populations of people with poorly controlled asthma when considering asthma symptoms or control.
A total of 931 participants were included (median age, 35 years; 63% female); 76% were aged 18 years or older.
A BDR was observed in 31%, 32%, 42%, and 34% of participants per definitions 1, 2, 3, and 4, respectively. Good agreement was observed among all definitions, with kappa coefficients ranging from 0.73 to 0.87. A total of 415 (45%) participants had a BDR by at least 1 definition, although 56% of these 415 participants had a BDR in all 4 definitions.
BDRs were more common in individuals who were male, Black, and had never smoked and less common in patients with obesity. Those with a BDR had lower lung function (FEV1 and FEV1/FVC) vs those without BDR.
BDR according to definitions 1 and 2 was associated with poor asthma control, and BDR based on definition 1 was weakly associated with greater symptom burden in univariate analysis.
After adjustment for potential confounders of age, sex, height, obesity, and baseline lung function (FEV1 z-score and FEV1/FVC z-score), BDR for any definition was not associated with asthma control or asthma symptom burden.
Study limitations include the lack of a comparator group of participants with completely controlled asthma and the use of baseline assessments only. In addition, there are other possible ways to measure BDR.
“How a BDR relates to other important clinical outcomes in other populations remains to be determined, but the findings of this study question the clinical utility of assessing a BDR in populations of people with poorly controlled asthma when considering asthma symptoms or control,” stated the investigators.
Disclosure: Some of the study authors declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of authors’ disclosures.
