Purpose
To build a questionnaire to assess health-related quality of life (HRQL) in patients suffering from slowly progressive neuromuscular disease (NMD) using item response theory (IRT).
Methods
A pool of 64 items and a validated questionnaire (WHOQOL-BREF) were administered to 159 patients recruited in eight NMD referral centers. Exploratory statistical analysis included methods derived from both IRT and classical test theory.
Results
We constructed a questionnaire named QoL–NMD which is composed of two general items and 24 items classified in three domains: (1) “Impact of Physical Symptoms,” (2) “Self-perception” and (3) “Activities and Social Participation.” Each domain has good psychometric properties (Cronbach’s alpha > 0.77, test–retest ICC > 0.81, Loevinger’s H > 0.41) and meets IRT assumptions. Comparison with the WHOQOL-BREF enabled assessing similarities and discrepancies with a generic questionnaire.
Conclusion
This study enabled the development of a new HRQL questionnaire specifically designed for slowly progressive NMD patients. The QoL–NMD is short enough to be used in clinical practice (26 items). The next steps will be to validate QoL–NMD by re-assessing psychometrics in an independent sample of patients and calibrate the IRT scoring system.
