Validity, invariance and responsiveness of a self-report measure of functional limitations and disability in multiple sclerosis.
OBJECTIVE
This study examined the structural and external aspects of score validity for the abbreviated Late Life-Function and Disability Inventory (LL-FDI) as well as its longitudinal measurement invariance and responsiveness in individuals with multiple sclerosis (MS).


METHODS
The sample included 292 individuals with MS who completed a battery of questionnaires on two occasions separated by 6 months. The battery included the abbreviated LL-FDI along with measures of mobility disability; neurological impairments; symptoms of fatigue, anxiety, depression and pain; health status; and quality of life. The data were analysed using Analysis of Moment Structures (AMOS) and Statistical Package for the Social Sciences (SPSS), versions 16.0.


RESULTS
Confirmatory factor analysis supported the structural validity and longitudinal measurement invariance of the disability and functional limitations components of the abbreviated LL-FDI. MANOVA and bivariate correlations supported the external aspects of score validity based on differences in mean scores as a function of clinical MS course (relapsing vs. progressive) and level of mobility disability (mild vs. moderate mobility disability) and associations with measures of neurological impairments, symptoms, health status and QOL, respectively. ANOVA established the responsiveness (i.e., sensitivity for reflecting clinically important differences in health status across time) of the functional limitations and disability components of the abbreviated LL-FDI for detecting changes in mobility disability across 6-months.


CONCLUSIONS
Such findings provide a new option for the measurement of functional limitations and disability using the abbreviated LL-FDI in persons with MS.
Department of Kinesiology and Community Health, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA. robmotl@uiuc.edu
Robert W
RW
Motl
Edward
E
McAuley
Yoojin
Y
Suh
D000328:Adult; D000368:Aged; D004185:Disability Evaluation; D018450:Disease Progression; D005163:Factor Analysis, Statistical; D005260:Female; D006304:Health Status; D006305:Health Status Indicators; D006801:Humans; D008297:Male; D008875:Middle Aged; D009103:Multiple Sclerosis / Q000534:rehabilitation*; D011594:Psychometrics; D015203:Reproducibility of Results