Multiple Sclerosis Severity Score: using disability and disease duration to rate disease severity.
BACKGROUND
There is no consensus method for determining progression of disability in patients with multiple sclerosis (MS) when each patient has had only a single assessment in the course of the disease.


METHODS
Using data from two large longitudinal databases, the authors tested whether cross-sectional disability assessments are representative of disease severity as a whole. An algorithm, the Multiple Sclerosis Severity Score (MSSS), which relates scores on the Expanded Disability Status Scale (EDSS) to the distribution of disability in patients with comparable disease durations, was devised and then applied to a collection of 9,892 patients from 11 countries to create the Global MSSS. In order to compare different methods of detecting such effects the authors simulated the effects of a genetic factor on disability.


RESULTS
Cross-sectional EDSS measurements made after the first year were representative of overall disease severity. The MSSS was more powerful than the other methods the authors tested for detecting different rates of disease progression.


CONCLUSIONS
The Multiple Sclerosis Severity Score (MSSS) is a powerful method for comparing disease progression using single assessment data. The Global MSSS can be used as a reference table for future disability comparisons. While useful for comparing groups of patients, disease fluctuation precludes its use as a predictor of future disability in an individual.
Roxburgh
R H S R
RH
Neurology Department, Cambridge University, UK. richard@roxburgh.net.nz
Seaman
S R
SR
Masterman
T
T
Hensiek
A E
AE
Sawcer
S J
SJ
Vukusic
S
S
Achiti
I
I
Confavreux
C
C
Coustans
M
M
le Page
E
E
Edan
G
G
McDonnell
G V
GV
Hawkins
S
S
Trojano
M
M
Liguori
M
M
Cocco
E
E
Marrosu
M G
MG
Tesser
F
F
Leone
M A
MA
Weber
A
A
Zipp
F
F
Miterski
B
B
Epplen
J T
JT
Oturai
A
A
Sørensen
P Soelberg
PS
Celius
E G
EG
Lara
N Téllez
NT
Montalban
X
X
Villoslada
P
P
Silva
A M
AM
Marta
M
M
Leite
I
I
Dubois
B
B
Rubio
J
J
Butzkueven
H
H
Kilpatrick
T
T
Mycko
M P
MP
Selmaj
K W
KW
Rio
M E
ME
Sá
M
M
Salemi
G
G
Savettieri
G
G
Hillert
J
J
Compston
D A S
DA
D000328:Adult; D017668:Age of Onset; D015331:Cohort Studies; D003430:Cross-Sectional Studies; D016208:Databases, Factual; D004185:Disability Evaluation; D018450:Disease Progression; D005260:Female; D005602:France / Q000453:epidemiology; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D008959:Models, Neurological; D015233:Models, Statistical; D009103:Multiple Sclerosis / Q000175:diagnosis* / Q000453:epidemiology / Q000503:physiopathology; D011237:Predictive Value of Tests; D011379:Prognosis; D012008:Recurrence; D015203:Reproducibility of Results; D012720:Severity of Illness Index