Age Related Multiple Sclerosis Severity Score: Disability ranked by age.
BACKGROUND
The Multiple Sclerosis Severity Score (MSSS) is obtained by normalising the Expanded Disability Status Scale (EDSS) score for disease duration and has been a valuable tool in cross-sectional studies.


OBJECTIVE
To assess whether use of age rather than the inherently ambiguous disease duration was a feasible approach.


METHODS
We pooled disability data from three population-based cohorts and developed an Age Related Multiple Sclerosis Severity (ARMSS) score by ranking EDSS scores based on the patient's age at the time of assessment. We established the power to detect a difference between groups afforded by the ARMSS score and assessed its relative consistency over time.


RESULTS
The study population included 26058 patients from Sweden ( n = 11846), Canada ( n = 6179) and the United Kingdom ( n = 8033). There was a moderate correlation between EDSS and disease duration ( r = 0.46, 95% confidence interval (CI): 0.45-0.47) and between EDSS and age ( r = 0.44, 95% CI: 0.43-0.45). The ARMSS scores showed comparable power to detect disability differences between groups to the updated and original MSSS.


CONCLUSIONS
Since age is typically unbiased and readily obtained, and the ARMSS and MSSS were comparable, the ARMSS may provide a more versatile tool and could minimise study biases and loss of statistical power caused by inaccurate or missing onset dates.
Department of Clinical Neuroscience (CNS), Karolinska Institutet, Stockholm, Sweden.
Ali
A
Manouchehrinia
Institute of Environmental Medicine (IMM), Karolinska Institutet, Stockholm, Sweden.
Helga
H
Westerlind
Division of Neurology, Faculty of Medicine, UBC Hospital, The University of British Columbia, Vancouver, BC, Canada.
Elaine
E
Kingwell
Division of Neurology, Faculty of Medicine, UBC Hospital, The University of British Columbia, Vancouver, BC, Canada.
Feng
F
Zhu
Division of Neurology, Faculty of Medicine, UBC Hospital, The University of British Columbia, Vancouver, BC, Canada.
Robert
R
Carruthers
Department of Clinical Neuroscience (CNS), Karolinska Institutet, Stockholm, Sweden.
Ryan
R
Ramanujam
Department of Clinical Neurosciences, University of Cambridge, Cambridge, UK.
Maria
M
Ban
Department of Clinical Neuroscience (CNS), Karolinska Institutet, Stockholm, Sweden.
Anna
A
Glaser
Department of Clinical Neurosciences, University of Cambridge, Cambridge, UK.
Stephen
S
Sawcer
Division of Neurology, Faculty of Medicine, UBC Hospital, The University of British Columbia, Vancouver, BC, Canada.
Helen
H
Tremlett
Department of Clinical Neuroscience (CNS), Karolinska Institutet, Stockholm, Sweden.
Jan
J
Hillert
D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D002170:Canada; D006233:Persons with Disabilities; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009103:Multiple Sclerosis / Q000175:diagnosis*; D012720:Severity of Illness Index; D013548:Sweden; D013997:Time Factors; D006113:United Kingdom; D055815:Young Adult
EDSS; MSSS; disability; disease severity; multiple sclerosis