Middle-range scores from the patient determined disease steps scale reflect varying levels of walking dysfunction in multiple sclerosis

Abstract

Background: Multiple sclerosis (MS) is a leading cause of neurological disability among young and middle-aged adults worldwide, and disability is measured using a variety of approaches, including patient reported outcome measures (PROMs) such as the Patient Determined Disease Steps (PDDS) scale. There is limited evidence for the validity of inferences from the middle-range of scores on the PDDS (i.e., 3 “gait disability” – 6 “bilateral support”), but that range of scores seemingly represents moderate disability characterized by varying levels of walking dysfunction. Purpose: The current study examined whether the middle-range of scores from the PDDS reflect varying levels of walking dysfunction among people with MS. Method: Participants (N = 374) completed the Patient Determined Disease Steps (PDDS) scale, Multiple Sclerosis Walking Scale-12 (MSWS-12), timed 25-foot walk (T25FW), six-minute walk (6 MW), Modified Fatigue Impact Scale (MFIS), and Multiple Sclerosis Impact Scale-29 (MSIS-29), and underwent a neurological exam for generating an Expanded Disability Status Scale (EDSS) score as part of screening and baseline data collection for a clinical trial of exercise training in MS. We undertook a series of linear trend analyses that examined differences in the outcomes of EDSS, T25FW, 6 MW, MSWS-12, MFIS subscales, and MSIS-29 subscales across the 4 levels of PDDS scores (i.e., 3–6). Results: There were statistically significant and strong linear trends for EDSS (F1,370 = 306.1, p