DEEP Study: does EQ-5D-5L measure the impacts of persistent oro-facial pain?

The EQ-5D-5L is a generic quality of life (QOL) measure widely used throughout the world, which has the advantage that it allows health-state preferences to be elicited. The aim of this study was to examine whether: a) variation in the standardised reference period for EQ-5D-5L from 'today' to 'the last month' had a minimal clinically meaningful difference; (b) EQ-5D-5L had convergent validity with a multidimensional pain measure in quantifying the impacts of pain. As part of a larger study into the effectiveness and efficiency of care pathways for persistent orofacial pain (POFP) (http://research.ncl.ac.uk/deepstudy), participants with POFP (n = 100) completed two versions of the EQ-5D-5L at the same time with different reference periods ('today' vs. 'last month'). Participants also completed the first section of the West Haven-Yale Multidimensional Pain Inventory (v3) to assess convergent validity. Two-tailed nonparametric inferential statistics, intra-class correlation coefficients (ICC), and within-subject change scores were used to compare the two EQ-5D-5L versions. Convergent validity was assessed using Spearman's rho correlation coefficients. Health-state valuations were significantly different (P < 0.01), and there was good similarity between the two versions' ICC 0.86 (95% CI 0.79-0.91). The within-subject mean change was 0.03 (95% CI 0.01-0.06). For convergent validity, all relationships were significant (P < 0.05) and in the expected directions. EQ-5D-5L demonstrates sufficient convergent validity to be used with POFP, and a change in the standard reference period may be unnecessary if a multidimensional pain measure is also used.