Medical care and treatments of patients suffering from slowly-progressive neuromuscular disease (NMD) mainly aim to improve health-related quality of life (HRQOL). To date there is no French HRQOL-measurement tool specifically designed for these patients. Recent works allowed developing a new questionnaire of 26 items named “Quality of Life in Neuromuscular Diseases” (QoL-NMD). It is structured in 3 domains and was constructed using focus groups: Delphi method and exploratory statistical analysis. Our objectives are to validate QoL-NMD using an independent sample and to calibrate the scoring system.

The QOL-NMD and a validated questionnaire (WHOQOL-BREF) were administered to 153 patients recruited in 8 tertiary hospitals dedicated to NMD. Confirmatory statistical analysis included methods derived from both Items Response Theory (IRT) and Classical Test Theory.

Data confirmed the results of the exploratory analysis. The 3 domains of QoL-NMD met IRT assumptions (i.e. unidimensionality, parameter invariance and monotonicity) and showed adequate psychometric properties (Cronbach > 0.7, H > 0.3, test-retest ICC > 0.7). Each domain was calibrated using a parametric IRT model. Comparison to WHOQOL-BREF allowed investigating similarities, discrepancies and putting forward QoL-NMD psychometric superiority.

This study led to the validation and calibration of a new HRQOL questionnaire specifically designed for NMD patients. It can now be used in various clinical settings. QoL-NMD has been translated and culturally adapted to English but still require a psychometric validation abroad.