Validation and comparison of 15-D and EQ-5D-5L instruments in a Spanish Parkinson's disease population sample

To contribute to the ongoing discussion on the choice of a preference-based health-related quality of life (HRQoL) instrument to be used in cost-effectiveness analysis by studying and comparing the validity, sensitivity and relative efficiency of 15-D and EuroQol 5D 5L (EQ-5D-5L) in a Spanish Parkinson's disease (PD) population sample. One hundred and thirty-three volunteers were asked to complete an interview using 15-D and EQ-5D-5L. Spearman's rank correlation coefficient (r) was used to test the convergent validity of these instruments with specific PD measures. Sensitivity and efficiency were compared using receiver operating characteristic (ROC) curves and relative efficiency statistic, respectively. A strong correlation (r > 0.65; p < 0.001) was found between both 15-D and EQ-5D-5L utilities with the summary score of the PDQ-8, and a strong correlation (r > 0.50; p < 0.001) was found between 15-D and EQ-5D-5L utilities with the EQ-VAS. The areas under the ROC of both instruments all exceeded 0.5 (p < 0.001). The 15-D instrument was 4.1-29.8 % less efficient at detecting differences between patients with optimal HRQoL, while this instrument was 11 % more efficient at detecting differences between patients at mild and moderate to strong severity of the PD symptoms. 15-D and EQ-5D-5L are showed to be valid and sensitivity generic HRQoL measures in Spanish PD patients with both instruments showing similar HRQoL dimension coverage and ceiling/floor effects. The 15-D has better efficiency and greater sensitivity to detect clinical changes in PD severity of the symptoms meanwhile the EQ-5D-5L is better to detect clinical HRQoL changes. Additionally, the EQ-5D-5L questionnaire requires less time than 15-D to be administered, and it might be more appropriate for studies conducted in Spain, since a country-specific value set is available for this instrument and not for the 15-D.