Development and validation of a muscular dystrophy-specific functional rating scale.
OBJECTIVE
To develop a reliable and valid new rating scale for measuring the functional impact of muscular dystrophy.


METHODS
Prospective and longitudinal investigation.


METHODS
Three academic medical centres in Taiwan and the Muscular Dystrophy Association of Taiwan.


METHODS
The Brooke Scale, the Vignos Scale, the Barthel Index, muscular strength, contracture severity, and predicted forced vital capacity (FVC%).


METHODS
Scale development was in three stages. In stage I, a preliminary pool of 53 items was generated from patient interviews (n = 25), literature review, existing functional rating scales and expert opinion. In stage II, these items were administered to 85 patients with muscular dystrophy. The resulting data were analysed to construct a rating scale (the Muscular Dystrophy Functional Rating Scale, MDFRS) that encompassed four unidimensional constructs: mobility, basic activities of daily living, arm function and impairment. In stage III, the measurement properties of this rating scale were assessed in 121 muscular dystrophy patients different from those examined with the preliminary instrument.


RESULTS
Internal consistency reliability was excellent for all domains of the final 33-item scale, with values of Cronbach's alpha ranging from 0.84 to 0.97. Intraclass correlation coefficients for test-retest and inter-rater reliability were 0.99 for all domains of the MDFRS. The MDFRS showed moderate to high correlations with a range of functional rating scales measuring similar aspects and impairment parameters (Spearman's rho = 0.65-0.91; P < 0.001, each). Confirmatory factor analysis supported a unitary construct of the four-dimensional MDFRS. The MDFRS had small floor and ceiling effects in the study samples. Sensitivity to change was confirmed by large standardized response means for the MDFRS total score.


CONCLUSIONS
The MDFRS is a reliable and valid disease-specific measure of functional status for patients with muscular dystrophy.
Lue
Yi-Jing
YJ
Faculty of Physical Therapy, College of Health Science, Kaohsiung Medical University, Kaohsiung, Taiwan. yijilu@cc.kmu.edu.tw
Su
Chwen-Yng
CY
Yang
Rei-Cheng
RC
Su
Wei-Lieh
WL
Lu
Yen-Mou
YM
Lin
Rong-Fong
RF
Chen
Shun-Sheng
SS
D000203:Activities of Daily Living; D000293:Adolescent; D000328:Adult; D001132:Arm / Q000503:physiopathology; D002648:Child; D004185:Disability Evaluation; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D051346:Mobility Limitation; D009119:Muscle Contraction / Q000502:physiology; D053580:Muscle Strength / Q000502:physiology; D009136:Muscular Dystrophies / Q000503:physiopathology*; D011446:Prospective Studies; D011594:Psychometrics; D015203:Reproducibility of Results; D012720:Severity of Illness Index; D014797:Vital Capacity / Q000502:physiology