Psychometric Properties of the Persian Version of Cystic Fibrosis Questionnaire: Revised in Children with Cystic Fibrosis

Background: Cystic fibrosis is a progressive, fatal disease affecting the quality of life. The cystic fibrosis questionnaire-revised (CFQ-R) is an efficient tool to monitor health-related quality of life in patients. The aim of this study was to explore the psychometric properties of the child and parent versions of the Persian version of the CFQ-R in the Iranian population.

Methods: Fifty children with cystic fibrosis (6-11 years) and their parents were allocated in this methodological study to examine convergent validity, discriminant validity, test-retest reliability (n = 30), internal consistency, ceiling and floor effects, and agreement between two versions of the CFQ-R.

Results: Convergent validity was confirmed for parent proxy (P < 0.05). CFQ-R discriminated patients among stages of disease severity based on lung function, age, and BMI (P < 0.05). Test-retest analysis revealed good to excellent reliability (inter-class correlation coefficient (ICC) = 0.78-0.97). In most domains, lower quality of life scores was obtained in the parent proxy compared to the child version (P < 0.05). Domain-specific correlations were found between the child version and parent proxy (P < 0.05). Internal consistency was generally confirmed (α = 0.13-0.83 in child version and α = 0.25-0.87 in parent proxy). There were no floor effects. Ceiling effects were mostly seen for physical, digestion, and body image domains in the child version and for eating, weight, and school domains in the parent proxy.

Conclusions: The child version and parent proxy of the Persian CFQ-R are valid and reliable measures and can be applied in clinical trials to monitor the quality of life in children with cystic fibrosis. It is recommended to use both versions in conjunction to better interpret the quality of life aspects of children with cystic fibrosis.