The quality of life in genetic neuromuscular disease questionnaire: Rasch validation of the French version.

INTRODUCTION: Slowly progressive, genetic neuromuscular diseases (gNMDs) often lead to important motor deficiencies and functional limitations. The Quality of Life in Genetic Neuromuscular Disease Questionnaire (QoL-gNMD) is a new health-related quality-of-life questionnaire developed for these patients. The purpose of the present study was to validate the French version of the QoL-gNMD and to calibrate its measurement system.

METHODS: Both the QoL-gNMD and a validated generic questionnaire (WHOQOL-BREF) were administered to patients. Validation was performed using item response theory. The partial credit model (Rasch) was used to calibrate each domain.

RESULTS: Three hundred fifteen adult patients were included. All 3 domains showed adequate psychometric properties (internal consistency: person separation index >0.77; repeatability: test-retest intraclass correlation coefficient >0.75, scalability coefficient >0.38) and fitted the partial credit model. The QoL-gNMD also demonstrated adequate concurrent validity with the WHOQOL-BREF.

DISCUSSION: The QoL-gNMD showed adequate psychometric properties and can be used in clinical settings. Although not anchor-based, the minimum detectable change tables help in interpreting score change. Muscle Nerve 56: 1085-1091, 2017.