Reliability and validity of the Italian version of the hand functional disability scale in patients with systemic sclerosis

The English version of hand functional disability scale is a validated instrument for measuring hand involvement in patients with systemic sclerosis (SSc). Because validation of multiple-language versions of existing validated questionnaires plays a key role in standardizing the outcome measurement and increasing the statistical power of clinical studies, this study aims to validate a translated Italian version of hand functional disability scale which is not available at the moment. The Italian version of hand functional disability scale was tested on 50 patients with SSc. To determine test–retest reliability, 40 SSc patients were asked to complete the questionnaire a second time within 2 weeks of the initial testing session. The test–retest reliability and internal consistency were determined by intra-class correlation coefficient (ICC) and Cronbach's α. External consistency was measured by comparing with an already validated test, the Health Assessment Questionnaire (HAQ), and clinical measurements. To explore the relationships among these variables, multiple correspondence analysis (MCA) was adopted. The statistical analysis of each domain and the total score revealed a good test–retest reliability (ICCs > 0.75) and internal consistency (Cronbach's α > 0.7). Furthermore, a good external consistency was confirmed by evaluating the differences between the distributions of hand functional disability scale score for SSc patients with or without hand involvement (arthralgias, arthritis, flexion contractures, and digital ulcers) and comparing results with those obtained for HAQ. Finally, MCA demonstrates a strong correlation among functional disability scale areas and HAQ scores. The hand functional disability scale is a self-administered questionnaire and it has been specially developed to measure hand impairment in patients with hand disorders. Our data support its validity and reliability in Italian SSc patients.