Convergent validation of EQ-5D-5L in patients with Parkinson's disease.

INTRODUCTION: The European Quality of Life Questionnaire 5 level version (EQ-5D-5L) is a recently updated instrument to assess Health-Related Quality of Life (HRQoL) that has not been validated extensively. The main objective of this study was to evaluate the internal consistency and convergent validation of the EQ-5D-5L in a large sample of subjects with Parkinson's disease (PD). METHODS: A cross-sectional study was carried out. Consecutive Mexican subjects with PD were included. HRQoL was assessed using the EQ-5D-5L and the PDQ-8. Validity of the EQ-5D-5L was assessed determining its association with clinical ratings of disease severity, as well as correlation with PDQ-8. Additionally, performance was evaluated along predefined groups based on clinical and demographic data of known determinants of quality of life. RESULTS: A total of 585 patients were included for this study. A strong correlation was found between EQ-5D-5L index and PDQ-8 index (Spearman's correlation coefficient=-0.75; p<0.001). Correlation between EQ-5D-5L index and PDQ-8 index remained strong (-0.60 to -0.78; p values <0.001) through all predefined groups. EQ-5D-5L scored higher in those patients with dyskinesia, wearing off, freezing, postural instability, cognitive impairment or depressive mood (p values <0.001). CONCLUSION: The EQ-5D-5L is a valid instrument for evaluating HRQoL in PD, performing adequately irrespective of heterogeneous clinical and demographic characteristics, and showing to be sensitive to features of advanced disease and treatment complications.