Black adults with asthma did not see significant differences in time to exacerbation after adding a long-acting beta-agonist to their inhaled corticosteroid treatment, compared with adding tiotropium, according to results from a randomized, open-label trial.
Moreover, genetic variations were not associated with differences in treatment response.
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The study, published online Oct. 27 in JAMA, enrolled 1,070 patients already taking or eligible for combination therapy with inhaled corticosteroids (ICS). More than 75% of patients were women, and the mean age was 45 years.
Dr. Michael E. Wechsler of Brigham and Women’s Hospital, Boston, and colleagues carried out their research at 20 primary care sites in the United States, with information on variation in ADRB2 Arg16Gly alleles captured (JAMA 2015 Oct 27;314[16]:1720-30). Patients were followed an average of 310 days.
Of 538 patients randomized to salmeterol or formoterol plus ICS, the mean number of exacerbations was 0.42 per person-year, compared with 0.37 per person-year in the 532 patients of the tiotropium plus ICS group (rate ratio, 0.90; P = .31).
The likelihood of being exacerbation free at 1 year was 74% for a long-acting beta-agonist (LABA) plus ICS, vs. 75.7% for tiotropium plus ICS (hazard ratio, 0.91; P = .47).
Other measures – including patient-reported outcomes, spirometry, rescue medication use, asthma deteriorations, and adverse events – did not differ significantly between treatment assignments. When stratified by genotype, there were no significant differences in hazard ratios for time to first exacerbation, mean number of exacerbations, or lung function at 6, 12, or 18 months.
“The study was performed in a population that bears a disproportionate burden of asthma morbidity and in whom questions have been raised about the relative efficacy and safety of LABAs,” Dr. Wechsler and colleagues wrote in their analysis.
“Because questions have been raised about whether efficacy studies correctly capture all the causes of morbidity, we conducted a clinical effectiveness study primarily in practicing physician offices,” the authors explained. “We used an outcome important to patients, physicians, and policy makers – asthma exacerbations.”
The investigators acknowledged as limitations of their study its open-label design and that asthma diagnoses were made by community physicians with no required objective testing. In addition, the study’s high discontinuation rate and poor medicine adherence were roughly equal between treatment groups and reflective of real-world practice, they noted.
The Agency for Heathcare Research and Quality funded the study. Dr. Wechsler and several coauthors disclosed consultant fees from multiple pharmaceutical manufacturers.