[Measuring preferences for depressive health states].

OBJECTIVE: The purpose of this study was to analyse the construct validity and the concurrent validity of the EuroQol instrument (EQ-5D self-classifier, EQ VAS and EQ-5D indices), time trade-off (TTO) and contingent valuation (willingness-to-pay) for preference-based valuation of depressive health states.

METHODS: A survey of a representative sample (N = 3522) of the non-institutionalised population aged 18 and above in Germany was conducted using the EQ-5D, TTO and contingent valuation as well as the SF-12 questionnaire. Construct validity was analysed by comparing 130 respondents in whom 12-month prevalence for major depression, minor depression, or dystimia according to DSM-IV was identified based on a version of the Composite International Diagnostic Interview (WMH-CIDI) to respondents without depressive disorders. Concurrent validity was analysed by assessing the correlation between these measures in the group with depressive disorders.

RESULTS: In the group with depressive disorders, problems in all EuroQol dimension except for mobility were significantly more frequent, and mean values of all analysed preference measures except for willingness-to-pay were less favourable than in the group without depressive disorders (EQ VAS score 67 vs. 78; EQ-5D index [VAS] 83 vs. 94; EQ-5D index [TTO] 0.81 vs. 0.91; TTO 0.89 vs. 0.95; always p < 0.001). In the group with depressive disorders, EQ VAS score and EQ-5D indices were significantly correlated one with another (ranging from r = 0.63 to r = 0.92) as well as with the mental and the physical component scale of the SF-12 (ranging from r = 0.26 to r = 0.45) and with willingness-to-pay (ranging from r = - 0.20 to r = - 0.22); besides, willingness-to-pay was significantly correlated with TTO (r = - 0.46).

CONCLUSIONS: The results of this study point to the construct validity and concurrent validity of preference measures in patients with depressive disorders.