Dissecting definitions of disability accrual in relapsing multiple sclerosis-Have we reached standardization yet?
Publisher DOI
PubMed ID
41351456
Abstract
Background
Distinguishing relapse-associated worsening (RAW) and progression independent of relapse activity (PIRA) has reshaped understanding of disability accumulation in relapsing multiple sclerosis (RMS). The influence of differing definitions of disability accrual on event rates and RAW/PIRA proportions remains uncertain.Methods
This observational cohort study used Austrian MS Treatment Registry data (2010-2024). A custom algorithm evaluated 1440 definitional variants of disability accrual with varying confirmation duration, baseline modeling, and RAW/PIRA classification, including recently proposed "standardized" criteria.Results
We included 3273 RMS patients (mean age 37.5 years; 67.8% female) with ⩾24 months follow-up, ⩾3 Expanded Disability Status Scale (EDSS) scores, and ⩾1 EDSS score per year, contributing 3525 follow-up periods. Depending on definition, disability accrual varied between 15.7% and 41.6% of follow-ups. PIRA accounted for 56.1%-86.3% of events across definitions, while up to 8.4% were ambiguously classified, mainly due to post-relapse re-baselining or relapses during the confirmation period. Even under "standardized" criteria, 144 definitional combinations remained, with event rates ranging from 19.1% to 21.7% and PIRA contribution varying widely from 59.8% to 85.8%.Conclusion
PIRA predominantly drives disability accrual, yet definitional variation substantially influenced event rates and RAW/PIRA proportions. Transparent reporting and further optimization of definitions are critical for improving comparability, interpretation, and clinical relevance in MS research and care.
Distinguishing relapse-associated worsening (RAW) and progression independent of relapse activity (PIRA) has reshaped understanding of disability accumulation in relapsing multiple sclerosis (RMS). The influence of differing definitions of disability accrual on event rates and RAW/PIRA proportions remains uncertain.Methods
This observational cohort study used Austrian MS Treatment Registry data (2010-2024). A custom algorithm evaluated 1440 definitional variants of disability accrual with varying confirmation duration, baseline modeling, and RAW/PIRA classification, including recently proposed "standardized" criteria.Results
We included 3273 RMS patients (mean age 37.5 years; 67.8% female) with ⩾24 months follow-up, ⩾3 Expanded Disability Status Scale (EDSS) scores, and ⩾1 EDSS score per year, contributing 3525 follow-up periods. Depending on definition, disability accrual varied between 15.7% and 41.6% of follow-ups. PIRA accounted for 56.1%-86.3% of events across definitions, while up to 8.4% were ambiguously classified, mainly due to post-relapse re-baselining or relapses during the confirmation period. Even under "standardized" criteria, 144 definitional combinations remained, with event rates ranging from 19.1% to 21.7% and PIRA contribution varying widely from 59.8% to 85.8%.Conclusion
PIRA predominantly drives disability accrual, yet definitional variation substantially influenced event rates and RAW/PIRA proportions. Transparent reporting and further optimization of definitions are critical for improving comparability, interpretation, and clinical relevance in MS research and care.
Date Issued
2026-02
Publication Type
Article
Subject(s)
Subjects
Multiple sclerosis
•
PIRA
•
RAW
•
definition
•
disability
•
progression
Language(s)
en
Author(s)
Bsteh, Gabriel | |
Krajnc, Nik | |
Guger, Michael | |
Di Pauli, Franziska | |
Kraus, Jörg | |
Enzinger, Christian | |
Hegen, Harald |
Additional Credits
Journal
Multiple Sclerosis Journal
Publisher
SAGE Publications
ISSN
1477-0970
1352-4585
Access(Rights)
open.access