Reliability and validity of a new dexterity questionnaire (DextQ-24) in Parkinson's disease

Background Patients with Parkinson's disease exhibit disturbed dexterity. Validated self-reported outcomes for dexterity in Parkinson's disease are lacking. The aim of this study was to investigate the reliability, content and construct validity of a new Dexterity Questionnaire 24. Methods One hundred and three patients with Parkinson's disease completed the Dexterity Questionnaire 24 (score range 24–96), at baseline and four weeks later. The internal consistency was determined. Test-retest reliability was assessed in a subgroup (N = 44). Standard error of measurements and the minimal detectable change were defined. The construct validity was examined in the whole group (N = 103). Floor and ceiling effects were investigated. Results The internal consistency of the Dexterity Questionnaire 24 was high (α = 0.91). High test-retest reliability was found (Intra Class Correlation Coefficient = 0.91, Confidence interval: 0.84–0.95). Standard error of measurement was 2.9 and minimal detectable change was 8 points. (i.e., 11%). Good structural, convergent and divergent validity of the Dexterity questionnaire 24 was found (r = 0.73 with Activities of Daily Living-subscale of the Parkinson's Disease Questionnaire-39, and r = 0.66, and r = 0.50, p-values all < 0.0001, respectively with the subscales II and III of the Movement Disorders Society-Unified Parkinson Disease Rating Scale). Low not significant correlations were found between the Dexterity Questionnaire 24 and the subscales stigma and social support (r = 0.20, and r = 0.14 respectively). No floor or ceiling effects were found for the total Dexterity Questionnaire 24. Conclusion The Dexterity Questionnaire 24 is valid and reliable for evaluating dexterity in patients with Parkinson's disease.