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The Multiple Sclerosis Performance Test MSPT: An iPad-Based Disability Assessment Tool
Published on: June 30, 2014
Estimating typical multiple sclerosis disability progression speed from clinical observations
Murray G Brown1, Mark Asbridge2, Vern Hicks3
1Department of Community Health and Epidemiology, Dalhousie University and Capital District Health Authority, Centre for Clinical Research, Halifax, Nova Scotia, Canada.
Introduction:
Multiple sclerosis (MS) is a chronic disease of the central nervous system. Estimates of MS natural history (NH) disability progression speed from clinical observations vary worldwide. This may reflect, in part, variance in censoring-bias) (missing observations) and assumptions about when irreversible disability progression events occurred. We test whether estimates of progression speed which assume midpoint survival time at irreversible disability endpoints are significantly faster than estimates which assume maximum survival time, and are more stable across study groups and time periods.
Methods:
Our Nova Scotia NH study population includes 2,240 definite relapsing-onset multiple sclerosis (R-MS) natural history patients with 18,078 Expanded Disability Status Scale (EDSS) clinical observations in study period 1979-2010. Progression speed is measured by rate-of-change in range EDSS 0-6 and by survival time at irreversible endpoints EDSS 1-9. Midpoint censoring-bias-reduction methods are applied to clinical observations.
Findings:
Typical EDSS increase per year in range EDSS 0-6, assuming midpoint survival time, is estimated to be 0.168 for all R-MS, 0.204 for eventually-DMD-treated patients and 0.155 for never-DMD-treated patients. Estimates assuming midpoint rather than maximum survival time are significantly faster: 16% faster for all R-MS natural history patients, 6% faster for eventually-DMD-treated patients, and 21% faster for never-DMD-treated patients. The variability of estimates across study groups and time periods decreased when midpoint survival time was assumed.
Conclusions:
Estimates of typical disease progression speed from 1979-2010 Nova Scotia clinical observations are sensitive to censoring-bias and to analysts' survival time assumptions. Censoring-bias-adjusted estimates of typical natural history disability progression speed in relapsing-onset multiple sclerosis patients are significantly faster, and less variable within and across study groups and time periods, than unadjusted estimates, and are, arguably, more relevant for various stakeholders. The application of censoring-bias-reduction methods to other multiple sclerosis clinical databases may reduce variability in estimates of disability progression speed worldwide.
Insights
Adjusting for missing data in multiple sclerosis (MS) studies reveals faster disability progression. This method reduces variability in natural history estimates for relapsing-onset MS patients.
Area of Science:
- Neurology
- Clinical Epidemiology
Background:
- Multiple sclerosis (MS) is a chronic central nervous system disease with variable natural history (NH) disability progression estimates.
- Discrepancies in MS progression speed estimates may stem from censoring bias and assumptions about irreversible disability events.
Purpose of the Study:
- To evaluate if midpoint survival time assumptions yield faster and more stable MS disability progression estimates compared to maximum survival time assumptions.
- To assess the impact of censoring-bias-reduction methods on the variability of MS natural history progression estimates.
Main Methods:
- Utilized data from 2,240 relapsing-onset MS (R-MS) patients in Nova Scotia (1979-2010) with 18,078 Expanded Disability Status Scale (EDSS) observations.
- Measured progression speed via rate-of-change in EDSS (0-6) and survival time at irreversible endpoints (EDSS 1-9).
- Applied midpoint censoring-bias-reduction methods to clinical observations.
Main Results:
- Estimates assuming midpoint survival time were significantly faster (16-21% faster) than those assuming maximum survival time.
- Typical EDSS increase per year was estimated at 0.168 for all R-MS patients.
- Variability in progression speed estimates decreased across study groups and time periods when midpoint survival time was assumed.
Conclusions:
- MS natural history disability progression speed estimates are sensitive to censoring bias and survival time assumptions.
- Censoring-bias-adjusted estimates for R-MS patients are faster and less variable, offering potentially greater relevance.
- Applying these bias-reduction methods to other MS databases could decrease worldwide variability in progression speed estimates.
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