Cross-Cultural Adaptation and Psychometric Evaluation of the Chinese Version of the Functional Disability Inventory.

Introduction: Chronic pain is a major public health issue affecting approximately one-fifth of children and adolescents worldwide, and it is also a common complaint among Chinese adolescents. Despite its impact on daily functioning in this population, culturally adapted tools for assessing pain-related disability are lacking. The Functional Disability Inventory (FDI) is a widely used measure for evaluating functional impairment, but its simplified Chinese version has yet to be validated. This study aimed to translate and culturally adapt the FDI into simplified Chinese to assess its reliability and validity in measuring pain-related functional disability among Chinese adolescents.

Methods: First, the FDI was translated into simplified Chinese according to international guidelines. Subsequently, 1569 adolescents (aged 10-18) completed six scales: FDI, the Pain Catastrophizing Scale (PCS), the Depression Anxiety Stress Scales (DASS-21), the Tampa Scale for Kinesiophobia (TSK), the Children's Somatization Inventory (CSI), and the Wong-Baker Faces Pain Scale (WBS). After that, psychometric properties were evaluated, including internal consistency reliability (Cronbach's α and McDonald's ω), test-retest reliability (intraclass correlation coefficient and Pearson correlation coefficient), convergent validity (correlations with the other scales). In addition, the sample of 224 pediatric patients with functional abdominal pain (aged 8-18) was drawn to analyze the clinical validity by performing receiver operating characteristic (ROC) analysis.

Results: The Chinese FDI demonstrated strong internal consistency (α = 0.86; ω = 0.86) and acceptable test-retest reliability (ICC = 0.63; Pearson correlation coefficient was 0.64). Convergent validity was supported by significantly moderate correlations with all the other scales, coefficients ranging from r = 0.30 to r = 0.50 (p < 0.01). ROC analysis revealed excellent clinical validity, with an optimal cutoff score of ≥ 15 [area under the curve (AUC) = 0.90, sensitivity = 0.78, specificity = 0.92] for distinguishing adolescents with chronic pain from healthy peers.

Conclusions: The simplified Chinese FDI is a reliable and valid tool for assessing pain-related functional disability in Chinese adolescents. Its psychometric properties align with global versions while accounting for cultural differences, making it suitable for clinical and research use.