The impact of treatment adherence on clinical and economic outcomes in multiple sclerosis: Real world evidence from Alberta, Canada

Background: Approximately 1 in 400 Albertans has multiple sclerosis (MS). The current study objective was to determine the real-world impact of adherence to disease-modifying therapies (DMTs) on healthcare utilization and costs among MS patients utilizing administrative data from the Alberta health system in Canada. Methods: MS patients were identified using a validated case definition (>= 1 inpatient record or >= 5 practitioner claims within 2 years) and the study index DMT was defined as the first claim for a DMT between 1 April 2011 and 31 March 2014. Treatment adherence was calculated using medication possession ratio (MPR), and patients with MPR >= 80% were considered adherent; healthcare utilization and costs were explored using multivariable negative binominal regression and logistic regression models. Results: The majority of the 2864 MS patients identified were females, aged 35-55 years old. Overall, 66% of patients were adherent. Compared to non-adherent patients, adherent patients had fewer ambulatory care visits (all-cause: 8.8 vs 10.9, p = 0.0012; MS-related: 4.3 vs 5.3; p = 0.001), physician visits (all-cause: 15.1 vs 18.2, p = 0.0001; MS-related: 3.6 vs 4.4; p = 0.0001), and hospitalizations (all-cause: 5.2% vs 10.2%, p< 0.0001; MSrelated: 1.2% vs 2.5%, p = 0.0088). After adjusting for potential confounding factors adherent patients had approximately 20% less physician visits (MS-related: IRR 0.82 (0.79,0.86), p < 0.0001; all-cause: IRR 0.83 (0.81,0.85), p < 0.0001) and ambulatory care visits (MS-related IRR 0.80 (0.77,0.84), p < 0.0001; all-cause: IRR 0.82 (0.80,0.84), p < 0.0001) and approximately 50% fewer hospitalizations (MS-related: OR 0.50 (0.28-0.89), p < 0.0001; all-cause: OR 0.48 (0.35-0.64), p < 0.0001) than non-adherent patients. Conclusions: The current study found a significant impact of non-adherence to MS therapy on increased health system utilization. These findings demonstrate the importance of treatment adherence on clinical decisionmaking for patients with MS.