Disability in multiple sclerosis

Abstract

To create a reference table of disability outcomes in multiple sclerosis (MS) that would enable patients to rank their disability relative to others' with similar disease duration and to develop a cost-effective research tool for comparing MS severity across patient populations and time periods. The North American Research Committee on Multiple Sclerosis (NARCOMS) Registry collects disability data from patients with MS on a validated, 9-point Patient-Determined Disease Steps (PDDS) scale. We compiled the Disability Expectancy Table, which displays cumulative frequencies of PDDS scores for each year of disease duration, from 0 to 45 years. We also tabulated disease duration-adjusted mean ranks of PDDS scores, referred to as Patient-derived MS Severity Scores (P-MSSS). The cohort consisted of 27,918 NARCOMS enrollees, 72.7% of whom were female and 90.1% of whom were white. Mean age at symptom onset was 30.1 ± 10.1 years, and age at enrollment was 47.1 ± 11.0 years. The Disability Expectancy Table and P-MSSS afford a detailed overview of disability outcomes in a large MS cohort over a 45-year period. In the first year of disease, 15% of patients reported need of ambulatory aid, and 4% needed bilateral assistance or worse; after 45 years of disease, 76% of patients required ambulatory aid, and 52% bilateral assistance or worse. Proportion of patients who reported minimal or no interference in daily activities (PDDS ≤ 1) declined from 63% in the first year to 8% after 45 years of disease. The Disability Expectancy Table allows individual patients to determine how their disability ranks relative to NARCOMS enrollees with the same disease duration. P-MSSS may be used to compare disability across patient populations and to track disease progression in patient cohorts. P-MSSS does not require a formal neurologic examination and may therefore find wide applicability as a practical and cost-effective outcome measure in epidemiologic studies.