Validation of patient determined disease steps (PDDS) scale scores in persons with multiple sclerosis

Background: The Patient Determined Disease Steps (PDDS) is a promising patient-reported outcome (PRO) of disability in multiple sclerosis (MS). To date, there is limited evidence regarding the validity of PDDS scores, despite its sound conceptual development and broad inclusion in MS research. This study examined the validity of the PDDS based on (1) the association with Expanded Disability Status Scale (EDSS) scores and (2) the pattern of associations between PDDS and EDSS scores with Functional System (FS) scores as well as ambulatory and other outcomes. Methods: 96 persons with MS provided demographic/clinical information, completed the PDDS and other PROs including the Multiple Sclerosis Walking Scale-12 (MSWS-12), and underwent a neurological examination for generating FS and EDSS scores. Participants completed assessments of cognition, ambulation including the 6-minute walk (6 MW), and wore an accelerometer during waking hours over seven days. Results: There was a strong correlation between EDSS and PDDS scores (ρ = .783). PDDS and EDSS scores were strongly correlated with Pyramidal (ρ = .578 & ρ = .647, respectively) and Cerebellar (ρ = .501 & ρ = .528, respectively) FS scores as well as 6 MW distance (ρ = .704 & ρ = .805, respectively), MSWS-12 scores (ρ = .801 & ρ = .729, respectively), and accelerometer steps/day (ρ = −.740 & ρ = −.717, respectively). Conclusion: This study provides novel evidence supporting the PDDS as valid PRO of disability in MS

Validity of the Timed Up and Go Test as a Measure of Functional Mobility in Persons With Multiple Sclerosis

Objective: To examine the validity of the timed Up and Go (TUG) test as a measure of functional mobility in persons with multiple sclerosis (MS) by using a comprehensive framework based on construct validity (ie, convergent and divergent validity). Design: Cross-sectional study. Setting: Hospital setting. Participants: Community-residing persons with MS (N=47). Interventions: Not applicable. Main Outcome Measures: Main outcome measures included the TUG test, timed 25-foot walk test, 6-minute walk test, Multiple Sclerosis Walking Scale-12, Late-Life Function and Disability Instrument, posturography evaluation, Activities-specific Balance Confidence scale, Symbol Digits Modalities Test, Expanded Disability Status Scale, and the number of steps taken per day. Results: The TUG test was strongly associated with other valid outcome measures of ambulatory mobility (Spearman rank correlation, rs=.71-.90) and disability status (rs=.80), moderately to strongly associated with balance confidence (rs=.66), and weakly associated with postural control (ie, balance) (rs=.31). The TUG test was moderately associated with cognitive processing speed (rs=.59), but not associated with other nonambulatory measures (ie, Late-Life Function and Disability Instrument-upper extremity function). Conclusions: Our findings support the validity of the TUG test as a measure of functional mobility. This warrants its inclusion in patients' assessment alongside other valid measures of functional mobility in both clinical and research practice in persons with MS

The reliability, precision and clinically meaningful change of walking assessments in multiple sclerosis

Background: Assessing walking impairment in those with multiple sclerosis (MS) is common, however little is known about the reliability, precision and clinically important change of walking outcomes. Objective: The purpose of this study was to determine the reliability, precision and clinically important change of the Timed 25-Foot Walk (T25FW), Six-Minute Walk (6MW), Multiple Sclerosis Walking Scale-12 (MSWS-12) and accelerometry. Methods: Data were collected from 82 persons with MS at two time points, six months apart. Analyses were undertaken for the whole sample and stratified based on disability level and usage of walking aids. Intraclass correlation coefficient (ICC) analyses established reliability: standard error of measurement (SEM) and coefficient of variation (CV) determined precision; and minimal detectable change (MDC) defined clinically important change. Results: All outcome measures were reliable with precision and MDC varying between measures in the whole sample: T25FW: ICC=0.991; SEM=1 s; CV=6.2%; MDC=2.7 s (36%), 6MW: ICC=0.959; SEM=32 m; CV=6.2%; MDC=88 m (20%), MSWS-12: ICC=0.927; SEM=8; CV=27%; MDC=22 (53%), accelerometry counts/day: ICC=0.883; SEM=28450; CV=17%; MDC=78860 (52%), accelerometry steps/day: ICC=0.907; SEM=726; CV=16%; MDC=2011 (45%). Variation in these estimates was seen based on disability level and walking aid. Conclusion: The reliability of these outcomes is good and falls within acceptable ranges. Precision and clinically important change estimates provide guidelines for interpreting these outcomes in clinical and research settings

Accuracy of StepWatch™ and ActiGraph accelerometers for measuring steps taken among persons with multiple sclerosis

Introduction There has been increased interest in the objective monitoring of free-living walking behavior using accelerometers in clinical research involving persons with multiple sclerosis (MS). The current investigation examined and compared the accuracy of the StepWatch activity monitor and ActiGraph model GT3X+ accelerometer for capturing steps taken during various speeds of prolonged, over-ground ambulation in persons with MS who had mild, moderate, and severe disability. Methods Sixty-three persons with MS underwent a neurological examination for generation of an EDSS score and undertook two trials of walking on the GAITRite electronic walkway. Participants were fitted with accelerometers, and undertook three modified six-minute walk (6MW) tests that were interspersed with 10–15 minutes of rest. The first 6MW was undertaken at a comfortable walking speed (CWS), and the two remaining 6MW tests were undertaken above (faster walking speed; FWS) or below (slower walking speed; SWS) the participant's CWS. The actual number of steps taken was counted through direct observation using hand-tally counters. Results The StepWatch activity monitor (99.8%–99.9%) and ActiGraph model GT3X+ accelerometer (95.6%–97.4%) both demonstrated highly accurate measurement of steps taken under CWS and FWS conditions. The StepWatch had better accuracy (99.0%) than the ActiGraph (95.5%) in the overall sample under the SWS condition, and this was particularly apparent in those with severe disability (StepWatch: 95.7%; ActiGraph: 87.3%). The inaccuracy in measurement for the ActiGraph was associated with alterations of gait (e.g., slower gait velocity, shorter step length, wider base of support). Conclusions This research will help inform the choice of accelerometer to be adopted in clinical trials of MS wherein the monitoring of free-living walking behavior is of particular value

Psychometric properties of the fatigue severity scale and the modified fatigue impact scale

Objective Fatigue is one of the most common, debilitating and life altering symptoms experienced by those with multiple sclerosis (MS) and has become the focus of therapeutic interventions and clinical rehabilitation. There is limited evidence regarding the psychometric properties and clinical relevance of fatigue outcomes for interpreting the effectiveness of intervention and rehabilitation strategies. This study determined the reliability, precision and clinically important change of the uni-dimensional Fatigue Severity Scale (FSS) and the multi-dimensional Modified Fatigue Impact Scale (MFIS). Methods The FSS and MFIS along with physical, psychological and cognitive clinical outcomes were administered to a sample of 82 persons with MS in a clinical research setting on two time points, separated by six months. Intraclass correlation coefficient (ICC) analyses established reliability; standard error of measurement (SEM) and coefficient of variation (CV) determined precision; minimal detectable change (MDC) defined clinically important change. Results Participants varied in type of MS and disability status, with 77% of participants classified as having substantial fatigue, based on the criteria of a mean FSS score ≥ 4. The MFIS (ICC = 0.863) and the FSS (ICC = 0.751) had acceptable reliability over six months. Precision was reasonable for both scales (based on SEM and CV estimates) but better for the FSS. MDC estimates were established and were lower for the FSS. Conclusion Reliability of the FSS and MFIS falls within acceptable ranges, and precision and clinically important change estimates provide guidelines for interpreting change in scores from these outcomes in clinical research of intervention and rehabilitation approaches for managing fatigue

Comparing two conditions of administering the Six-Minute walk test in people with Multiple Sclerosis

Objective: This quasi-experimental study was conducted to determine whether differences existed in the total distance walked and energy expended between two conditions of administering the 6-Minute Walk test (6MW) across different levels of disability in people with multiple sclerosis (MS). Methods: The sample comprised 160 individuals with MS. One group of participants (n = 82) completed a 6MW while wearing a portable metabolic unit (K4b2, Cosmed, Italy) in a square hallway with four corridors and performing 90° turns. Another group (n = 78) completed a 6MW while wearing the same metabolic unit in a single corridor and performing 180° turns. Main outcome measures included total distance walked (in feet) and oxygen consumption (in milliliters per minute) expressed as 30-second averages for 1 minute before the 6MW and over the entire 6MW. Disability status was assessed using the Patient-Determined Disease Steps scale. Results: Participants undertaking the 6MW in a single corridor (1412 ft) walked 37 ft (2.7%) farther than those undertaking the test in a square hallway (1375 ft), but this difference was not statistically significant (F = 0.45, P = .51). Those completing the 6MW in a single corridor expended more energy than those completing the 6MW in the square hallway with four corridors (F = 3.41, P < .01). Conclusions: Either protocol is acceptable, but researchers should be aware of the additional physiological demands when administering the 6MW in a single corridor with 180° turns

Cognitive motor interference during walking in Multiple Sclerosis using an alternate-letter alphabet task

Objective To examine cognitive motor interference (CMI) during walking using a simple, standardized, and well-refined alphabet dual-task (DT) paradigm in individuals with multiple sclerosis (MS) in whom cognitive and walking impairment often co-occur. Design A single time point, cross-sectional study. Setting A university clinical laboratory. Participants Individuals with MS (N=61; mean age ± SD, 50.8±9.3y) performed 4 walking trials over a 4.6-m walkway to determine gait parameters. Interventions Not applicable. Main Outcome Measures Gait parameters were assessed over 4 walking trials. The first 2 walks involved the single task (ST) of walking only; the second 2 walks involved participants performing the DT of reciting alternate letters of the alphabet while walking. The gait parameters recorded during the ST and DT walks were used to compute a dual-task cost (DTC) of walking (% change in gait parameter between ST and DT walks) as a metric of CMI. Results Our multivariate analysis with univariate follow-ups indicated CMI during walking based on slower velocity (ηp2=.59; F=84.6; P<.001) and cadence (ηp2=.46; F=51.6; P<.001), shorter step length (ηp2=.38; F=36; P<.001), and increased step time (ηp2=.34; F=31; P<.001) and double-support time (ηp2=.31; F=27.3; P<.001) in DT versus ST conditions. The DTC of walking for the gait parameters was not correlated with clinical (disability, disease duration) and demographic (eg, education, age) factors (all |r|≤.240). Conclusions The alphabet DT paradigm is easily administered and well refined. We highlight its ability and acceptability to determine CMI during walking in people with MS, independent of disease status

Physical Fitness Assessment Across the Disability Spectrum in Persons With Multiple Sclerosis

Background and Purpose: Appropriate assessment of physical fitness (ie, aerobic capacity and muscular strength) is necessary for the design and evaluation of exercise training in multiple sclerosis (MS). However, this is challenging in persons with substantial disability, because of physical inaccessibility and insensitivity of certain exercise testing modalities. This study compared different methods of measuring cardiorespiratory (arm ergometer vs recumbent stepper) and muscular (hand-held dynamometry vs computerized dynamometry) fitness across the MS disability spectrum. Associations between physical fitness and other measures that represented all domains of the International Classification of Functioning, Disability and Health (ICF) were also examined. Methods: Sixty-four participants with MS completed 2 symptomlimited cardiorespiratory fitness and muscular strength tests.We also assessed disability, cognition, fatigue, walking speed and endurance, health-related quality of life, and activities of daily living. Results: Across all levels of disability, peak aerobic capacity assessed by recumbent stepping was higher compared with arm ergometry (P < 0.001). Peak torque of the knee extensors and knee flexors was significantly higher assessed by computerized dynamometry compared with hand-held dynamometry (P<0.001). Aerobic capacity and peak torque decreased as a function of increasing disability (P < 0.001). Significant, moderate to strong correlations were observed between the physical fitness measures and measures representing all domains of the ICF, irrespective of the fitness testing mode. Discussion and Conclusions: Overall, peak physical capacity was higher when assessed by recumbent stepping and computerized dynamometry. The assessment and prescription of exercise inMS should be based on these modalities to provide the most appropriate stimulus for exercise training adaptations. There continues to be an important association between physical fitness and other measures that represent all domains of the ICF, regardless of fitness assessment mode