Reliability and validity of the Medical Research Council (MRC) scale and a modified scale for testing muscle strength in patients with radial palsy.
OBJECTIVE
To assess the inter-rater and intra-rater reliability and validity of the original and a modified Medical Research Council scale for testing muscle strength in radial palsy.


METHODS
Prospective, randomized validation study.


METHODS
Thirty-one patients with peripheral paresis of radial innervated forearm muscles were included.


METHODS
Wrist extension, finger extension and grip strength were evaluated by manual muscle testing. Dynamometric measurement of grip strength was performed. Pair-wise weighted kappa coefficients were calculated to determine inter-rater and intra-rater reliability. The 2 scores were compared using the signed-rank test. Spearman's correlation coefficients of the maximal relative force measurements with the median (over-raters) Medical Research Council and modified Medical Research Council scores were calculated to determine validity.


RESULTS
Inter-rater agreement of the Medical Research Council scale (finger extension: 0.77; wrist extension: 0.78; grip strength: 0.78) and the modified Medical Research Council scale (finger extension: 0.81; wrist extension: 0.78; grip strength: 0.81) as well as intra-rater agreement of the Medical Research Council scale (finger extension: 0.86; wrist extension: 0.82; grip strength: 0.84) and the modified Medical Research Council scale (finger extension: 0.84, wrist extension: 0.81; grip strength: 0.88) showed almost perfect agreement. Spearman's correlation coefficients of the maximal relative force measurements with the median Medical Research Council and modified Medical Research Council score were both 0.78.


CONCLUSIONS
Medical Research Council and modified Medical Research Council scales are measurements with substantial inter-rater and intra-rater reliability in evaluating forearm muscles.
Paternostro-Sluga
Tatjana
T
Department of Physical Medicine and Rehabilitation, Medical University of Vienna, Austria. tatjana.paternostro-sluga@akhwien.at
Grim-Stieger
Martina
M
Posch
Martin
M
Schuhfried
Othmar
O
Vacariu
Gerda
G
Mittermaier
Christian
C
Bittner
Christian
C
Fialka-Moser
Veronika
V
D000328:Adult; D000368:Aged; D005260:Female; D018737:Hand Strength / Q000502:physiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D053580:Muscle Strength / Q000502:physiology*; D018908:Muscle Weakness / Q000503:physiopathology* / Q000534:rehabilitation; D015588:Observer Variation; D011446:Prospective Studies; D020425:Radial Neuropathy / Q000503:physiopathology* / Q000534:rehabilitation; D015203:Reproducibility of Results