Oromandibular dystonia questionnaire (OMDQ-25): a valid and reliable instrument for measuring health-related quality of life.

OBJECTIVE

To develop and validate a disease-specific instrument to measure health-related quality of life in patients with oromandibular dystonia.

DESIGN

Prospective, cross-sectional observational study.

SETTING

Tertiary referral clinic, North East England, UK.

METHODS

The Oromandibular Dystonia Questionnaire (OMDQ-25) was evaluated in a group of 30 patients for psychometric properties, including its sensitivity to change after Botulinum Toxin A treatment. Comparison to a generic instrument was enabled using the Glasgow Health Scale Inventory and the Glasgow Benefit Inventory (GBI).

RESULTS

Item generation passed tests for scaling assumptions. Reliability was proven (Cronbach's α > 0.78; test-retest > 0.9) and validity supported with both convergent validity and discriminant validity. Sensitivity to change after Botulinum Toxin A treatment was established for all subscales (P ≤ 0.005), and in comparison with the GBI, all subscales showed large effect sizes.

CONCLUSION

The Oromandibular Dystonia Questionnaire (OMDQ-25) is the first reliable and valid instrument to measure health-related quality of life in patients with oromandibular dystonia.