Medication use patterns associated with spirometry in diagnosing COPD

Spirometry is necessary to diagnose and assess severity of COPD, but is used infrequently. Therapy with inhaled medications can improve COPD outcomes, but are not without risks. The use of spirometry may help mitigate the therapy risks if treatment is appropriate based on spirometry results. Before determining benefits of spirometry use, it is important to examine use of medications and the use of spirometry. Our objective was to characterize the association between the use of spirometry and respiratory medications in newly diagnosed COPD. This is a retrospective, longitudinal study using data from the Department of Veterans Affairs. We identified patients with a new diagnosis of COPD (index date). Spirometry use was measured two years before to six months after the index date. Respiratory medications were measured within one year following the index date. The association between spirometry and medication use was evaluated using logistic regressions and stratified by quintiles of the propensity scores for the probability of having had spirometry performed. A total of 81,162 patients were included and 30.8% had a spirometry performed. Patients with spirometry were more likely to have been dispensed an inhaled corticosteroid (AOR = 1.22 (95% CI, 1.11-1.36) to 1.61 (1.45-1.79)), long-acting beta-agonists (AOR = 1.41(1.25-1.58) to 1.63(1.45-1.83)), and ipratropium bromide (AOR = 1.25(1.16-1.35) to 1.64 (1.49-1.81)) across quintiles. Patients with spirometry were more likely to have medications added. The use of spirometry around a new diagnosis of COPD was associated with higher likelihood of using and adding respiratory medications after diagnosis.