Use of a claims-based algorithm to estimate disease severity in the multiple sclerosis Medicare population.

BACKGROUND/OBJECTIVE To compare algorithm determined disease severity, risk of multiple sclerosis (MS) relapse, and MS-related hospitalization between the age-eligible and disability-eligible MS Medicare populations. METHODS Using the Humana claims dataset (2013 - 2015), patients were divided into Medicare age-eligible and disability-eligible groups. A previously developed algorithm, which used MS symptoms and healthcare utilization to categorize MS disease severity into three groups (low, moderate, high) at baseline was employed. Flexible parametric and Cox proportional hazard models were used to estimate the risk for MS relapses and MS-related hospitalizations among the MS disease severity groups and the two eligibility cohorts in the follow-up period. RESULTS Of the overall sample (N = 6,559), the majority (N = 4,813, 73.4%) were disability-eligible and in the low disease severity group (N = 4,468, 68.1%). In 10 of 16 disease severity algorithm predictors, the prevalence of these predictors was significantly (p<0.001) higher in the disability-eligible group compared to the age-eligible group. Survival analyses revealed that the disability-eligible group had a significantly higher risk for follow-up MS relapses and follow-up MS-related hospitalizations (HR = 1.79 [CI 1.54 - 2.08] and HR = 1.38 [CI 1.11-1.72], respectively) compared to those in the age-eligible group. When both eligibility and disease severity were considered in the model increases in hazard ratios corresponded generally to increases in disease severity. However, the type of Medicare eligibility does not appear to have a clear pattern across MS disease severity groups for either MS relapse or hospitalizations, CONCLUSION: The disability-eligible Medicare population had a significantly higher prevalence of MS comorbidities and higher MS severity scores at baseline. In addition, they had a higher risk for MS-related relapses and MS-related hospitalizations in the follow-up period. It is important to account for disability status when assessing disease severity and healthcare utilization.