Validation of The Individualized Neuromuscular Quality of Life in Japanese patients with myotonic dystrophy

Introduction: The Individualized Neuromuscular Quality of Life (INQoL) is used to measure the quality of life (QoL) of patients with neuromuscular disease. We conducted this study to translate and validate the Japanese version of the INQoL in patients with myotonic dystrophy.

Methods: Forward and backward translation, patient testing, and psychometric validation were performed. We used the 36-Item Short Form Health Survey (SF-36) and the modified Rankin scale for concurrent validation.

Results: The Japanese INQoL was administered to 90 adult patients. The coefficients for internal consistency and test-retest reliability were adequately high in most domains (Cronbach α 0.88-0.96 and intraclass coefficient 0.64-0.99). INQoL domains were moderately to strongly associated with relevant SF-36 subscales (Spearman's ρ -0.23 to -0.74). Symptom severity, disease duration, employment status, and use of a ventilator influenced overall QoL.

Discussion: The INQoL is a reliable and validated measure of QoL for Japanese patients with myotonic dystrophy. Muscle Nerve, 2018.