The Gilles de la Tourette Syndrome–Quality of Life Scale (GTS-QOL): Development and validation
Cavanna AE., Schrag A., Morley D., Orth M., Robertson MM., Joyce E., Critchley HD., Selai C.
Background: Gilles de la Tourette syndrome (GTS) is a chronic neuropsychiatric disorder which has a significant detrimental impact on the health-related quality of life (HR-QOL) of patients. However, no patient-reported HR-QOL measures have been developed for this population.Objective: The development and validation of a new scale for the quantitative assessment of HR-QOL in patients with GTS.Methods: In stage 1 (item generation), a pool of 40 potential scale items was generated based on interviews with 133 GTS outpatients, literature review, and consultation with experts. In stage 2 (scale development), these items were administered to a sample of 192 GTS outpatients. Standard statistical methods were used to develop a rating scale satisfying criteria for acceptability, reliability, and validity. In stage 3 (scale evaluation), the psychometric properties of the resulting scale were tested in a second sample of 136 subjects recruited through the UK-Tourette Syndrome Association.Results: Response data analysis and item reduction methods led to a final 27-item GTS-specific HR-QOL scale (GTS-QOL) with four subscales (psychological, physical, obsessional, and cognitive). The GTS-QOL demonstrated satisfactory scaling assumptions and acceptability; both internal consistency reliability and test-retest reliability were high (Cronbach alpha ≥0.8 and intraclass correlation coefficient ≥0.8); validity was supported by interscale correlations (range 0.5–0.7), confirmatory factor analysis, and correlation patterns with other rating scales and clinical variables.Conclusions: The Gilles de la Tourette syndrome (GTS)–specific health-related quality of life (HR-QOL) scale (GTS-QOL) is proposed as a new disease-specific patient-reported scale for the measurement of HR-QOL in patients with GTS, taking into account the complexity of the clinical picture of GTS.