Anti-inflammatory Medication Adherence and Cost and Utilization of Asthma Care in a Commercially Insured Population
Published In: The Journal of Asthma, v. 47, no. 3, Apr. 2010, p. 323-329
Posted on RAND.org on December 31, 2009
OBJECTIVE: The authors hypothesized that adherence to anti-inflammatory treatment could reduce overall cost of asthma care, as higher spending on drugs would be offset by reductions in hospital and emergency care. METHODS: A retrospective observational study using 2 years of claims data for 41,234 commercially insured asthmatics on monotherapy with either leukotriene inhibitors (LI) or inhaled corticosteriods (ICS). Patients were grouped into adherence quartiles based on the percentage of days per year they had prescriptions filled (medication possession ratio). The relationship between adherence and four outcomes was examined: (1) emergency department (ED) visits, (2) hospitalizations, (3) nondrug net payments for asthma care, (4) total net payments for asthma care (including drug costs). Multivariate and logistic regression models adjusting for demographics, comorbidities, and measures of past asthma utilization were used. RESULTS: Adherence rates were low with a median medication possession ratio of 39% for LI and 15% for ICS. Both ED and hospital use was negatively associated with adherence to LI. Patients in the lowest quartile experienced 80 (95% confidence interval (CI) = 62-102) ED visits and 34 (95% CI = 22-52) admissions per 1000 patient-years compared to 36 (95% CI = 27-49) ED visits and 13 (95% CI = 8-22) admissions in the highest quartile. In contrast, ED visits and hospital admissions did not differ significantly between adherence groups for ICS. Total payments for asthma care increased significantly with higher adherence for both LI and ICS patients. Comparing the lowest and highest adherence quartile, payments per person per month increased significantly from $65.11 (95% CI = $57.02-$73.20) to $147.46 (95% CI = $139.48-$155.44) for patients on LI and from $38.71 (95% CI = $29.52-$47.90) to 93.13 (95% CI = $83.70-$102.56) for patients on ICS. The only subgroup, for which overall asthma payments did not increase with better adherence, were patients with past ED visit or hospital admission on LI. CONCLUSIONS: In this observational study, treatment with LI, but not with ICS, appears to improve disease control, as evidenced by the reduction in the incidence of ED visits and hospitalizations in patients on LI. Savings generated by this reduction in high-cost events don't offset the increased payments for drugs in more adherence patients, except for selected high-risk patients.