Serbian Validation of the Individualized Neuromuscular Quality of Life Questionnaire (INQoL) in Adults With Myotonic Dystrophy Type 1

Background: To validate Individualized Neuromuscular Quality of Life Questionnaire (INQoL) in Serbian patients with myotonic dystrophy type 1 (DM1). Methods: This study included 102 patients with adult onset DM1. Validation included reliability analysis (internal consistency, re-producibility), content-related validity (psychometric evaluation, construct-related validity, criterion-related validity) and concurrent validity. Results: The internal consistency of the Serbian version of INQoL was excellent (Cronbach’s alpha 0.864-0.961). Test-retest reliabil-ity satisfi ed the requested level (intraclass correlation coeffi cient 0.713-0.979). Item internal consistency and discriminant validity were excellent. INQoL scores were signifi cantly affected by age of patients, duration of disease and severity of muscular impairment (P < 0.01), slightly affected by education (P < 0.05) and not related to gender (P> 0.05). Correlation between INQoL scales and com-parable SF-36 domains was signifi cant (P < 0.01) but INQoL also registered locking and body image omitted by SF-36. Conclusions: Serbian version of INQoL is reliable and valid quality of life (QoL) measure for patients with DM1, able to capture disease specifi c issues usually omitted by generic questionnaires