Use of ICS/LABA on Asthma Exacerbation Risk in Patients Within a Medical Group

BACKGROUND: Asthma medication ratio (AMR) ≥ 0.5 has been shown to predict asthma exacerbations. This study explores the impact of increasing or decreasing inhaled corticosteroid/long-acting beta-agonist (ICS/LABA) use over a 7-year period on achieving an AMR of ≥ 0.5. OBJECTIVES: To (a) assess the impact of increasing use of ICS/LABAs on changes in a modified AMR (mAMR) and (b) examine asthma risk over time as measured by an mAMR over a 7-year period, adjusting for differences in baseline characteristics. METHODS: This is a retrospective, observational study using pharmacy and medical claims from a medical group from January 1, 2003, to December 31, 2010. All patients with ≥ 1 asthma diagnosis (ICD-9-CM, 493.xx) with ≥ 1 inhaled asthma medication dispensed in each year of eligibility were included. The mAMR = total ICS controllers dispensed/(total ICS controllers dispensed + albuterol dispensed). The proportion of ICS/LABA use was determined as the number of ICS/LABA canisters dispensed/(total of ICS/LABA + ICS dispensed). Generalized linear mixed models were used to assess the effect of incremental change in ICS/LABA use on mAMR over 7 years, adjusting for differences in resource utilization, time, and asthma medication use. RESULTS: Nine hundred ninety patients (mean age [± SD] 34.7 years [± 18.2], 61.7% female) met all criteria. Overall, mean mAMR increased over time, while mean albuterol use decreased over time. Adjusting for covariates, we found that a 10% increase in ICS/LABA use was associated with a 9% increase (adjusted OR = 1.09, 95% CI = 1.06-1.12) in the likelihood of achieving an mAMR ≥ 0.5, while a 50% increase in ICS/LABA use was associated with a 53% increase (OR = 1.53, 95% CI = 1.31-1.80) in the likelihood of achieving an mAMR ≥ 0.5. CONCLUSIONS: Increase in ICS/LABA use over time in a population of asthma patients was significantly associated with a higher likelihood of achieving an mAMR ≥ 0.5.