The patient knows best: significant change in the physical component of the Multiple Sclerosis Impact Scale (MSIS-29 physical).
OBJECTIVE
The aims of this study were to determine the reliability, responsiveness and minimally important change score of the Multiple Sclerosis Impact Scale (MSIS)-29 physical using the Expanded Disability Status Scale (EDSS) as an anchor measure.


METHODS
214 patients with multiple sclerosis (MS) (EDSS 0-8.5) had concurrent MSIS-29 and EDSS assessments at baseline and at up to 4 years of follow-up.


RESULTS
116 patients had unchanged EDSS scores. Stability of the MSIS-29 physical (mean change 0.1 points) was better in the 85 patients with EDSS 0-5.0 than in the 31 patients with EDSS 5.5-8.5 in whom the MSIS-29 physical score fell by 8 points, a response shift phenomenon. A floor effect for the MSIS-29 was observed in 5% of stable patients at both time points. 98 patients experienced EDSS change with moderately strong statistically significant correlations between change scores in the EDSS and the MSIS-29 physical (r = 0.523, p<0.0001). Effect sizes for MSIS-29 physical change were moderate to large. Using receiver operating characteristic curves, the MSIS-29 change score which produced a combination of optimal sensitivity and specificity was chosen for both EDSS ranges. For EDSS range 5.5-8, a change score of 8 had a sensitivity of 87% and specificity of 67%. For EDSS 0-5.0, a change score of 7 had a sensitivity of 78% and a specificity of 51%.


CONCLUSIONS
The MSIS-29 physical performs well over time, and is suitable for use in trials; a minimal change score of 8 points in the MSIS-29 is clinically significant.
Costelloe
Lisa
L
Department of Neurology, St Vincent's University Hospital, Dublin 4, Ireland.
O'Rourke
Killian
K
Kearney
Hugh
H
McGuigan
Christopher
C
Gribbin
Lisa
L
Duggan
Marguerite
M
Daly
Leslie
L
Tubridy
Niall
N
Hutchinson
Michael
M
D015331:Cohort Studies; D006233:Persons with Disabilities; D018450:Disease Progression; D006304:Health Status; D006801:Humans; D009103:Multiple Sclerosis / Q000150:complications*; D012372:ROC Curve; D012016:Reference Values; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012720:Severity of Illness Index