English cross-cultural translation and validation of the neuromuscular score: a system for motor function classification in patients with neuromuscular diseases

Abstract : Objective: To develop and validate an English version of the Neuromuscular (NM)-Score, a classification for patients with NM diseases in each of the 3 motor function domains: D1, standing and transfers; D2, axial and proximal motor function; and D3, distal motor function. Design: Validation survey. Setting: Patients seen at a medical research center between June and September 2013. Participants: Consecutive patients (N=42) aged 5 to 19 years with a confirmed or suspected diagnosis of congenital muscular dystrophy. Interventions: Not applicable. Main Outcome Measures: An English version of the NM-Score was developed by a 9-person expert panel that assessed its content validity and semantic equivalence. Its concurrent validity was tested against criterion standards (Brooke Scale, Motor Function Measure [MFM], activity limitations for patients with upper and/or lower limb impairments [ACTIVLIM], Jebsen Test, and myometry measurements). Informant agreement between patient/caregiver (P/C)-reported and medical doctor (MD)-reported NM scores was measured by weighted kappa. Results: Significant correlation coefficients were found between NM scores and criterion standards. The highest correlations were found between NM-score D1 and MFM score D1 (rho =-.944, P<.0001), ACTIVLIM (rho =-.895, P<.0001), and hip abduction strength by myometry (rho =-.811, P<.0001). Informant agreement between P/C-reported and MD-reported NM scores was high for D1 (kappa=.801; 95% confidence interval [CI],.701-.914) but moderate for D2 (kappa=.592; 95% CI,.412-.773) and D3 (kappa =.485; 95% CI,.290-.680). Correlation coefficients between the NM scores and the criterion standards did not significantly differ between P/C-reported and MD-reported NM scores. Conclusions: Patients and physicians completed the English NM-Score easily and accurately. The English version is a reliable and valid instrument that can be used in clinical practice and research to describe the functional abilities of patients with NM diseases.