Bronchodilator reversibility in patients with COPD revisited: short-term reproducibility

Categorization of patients with COPD as reversible or nonreversible to a bronchodilator may change over time. This post hoc analysis aimed to determine if an individual's reversibility, when treated as a continuous variable, could predict his/her future response to two short-acting bronchodilators: albuterol and ipratropium. The analysis was completed using data from a 4-week, randomized, open-label, two-period crossover study (NCT01691482; GSK study DB2114956). Patients received albuterol (doses: UK =4×100 μg/puff; US =4×90 μg/puff) followed 1 hour later by ipratropium (4×20 μg/puff) or vice versa during treatment Period 1. The order of treatments was reversed during Period 2. Predefined efficacy end points included pre- and post-bronchodilator forced expiratory volume in 1 second. The correlation coefficient between bronchodilator response on Days 1 and 10 was investigated, as well as the correlation between treatment response on Day 1 and the mean treatment response on Days 5-10, for each individual patient. Bronchodilator response to albuterol on Day 1 was strongly correlated with that on Day 10 (r=0.64; n=53). The correlation coefficient of bronchodilator treatment response on Day 1 and Days 5-10 was 0.78 (P<0.001; n=53) and 0.76 (P<0.001; n=54) for albuterol and ipratropium, respectively. A single measurement of the initial bronchodilator response to albuterol or ipratropium was, therefore, highly correlated with the subsequent mean bronchodilator response over 5-10 days, demonstrating its potential usefulness for future treatment decisions.