What is measured by the composite, single-item pain/discomfort dimension of the EQ-5D-5L? An exploratory analysis

This study examines the EQ-5D-5L pain/discomfort dimension by drawing comparisons with five other pain and discomfort items (pain severity, discomfort severity, pain frequency, discomfort frequency and pain interference) collected in the Australian psychometric study for the EQ Health and Wellbeing instrument.

Participants, recruited via a market research company, completed an online survey. Methods of analyses included the assessment of descriptive statistics, variation in reporting patterns using chi-square tests and cross-tabulations, correlation analyses, ordered univariate logistic regression, and discriminatory power analyses (Shannon index (H') and Shannon Evenness index (J')).

Survey data from 514 participants were used. Compared with EQ-5D-5L pain/discomfort, there was a higher proportion of respondents reporting some level of impairment on at least one of the pain severity and discomfort severity items (74% versus 81%). Correlation with EQ-5D-5L pain/discomfort was strongest for pain severity (r = 0.83) and weakest for discomfort frequency (r = 0.41); the same inferences were drawn for predictive ability. Adding any additional pain or discomfort items to the EQ-5D-5L increased the absolute informativity (H') but not the relative informativity (J'). When replacing EQ-5D-5L pain/discomfort with separate pain and/or discomfort items - i.e., adding items to a modified 'EQ-4D-5L'-absolute informativity increased, while relative informativity increased only when pain interference and frequency-related items (independently or in combination) were added.

The EQ-5D-5L pain/discomfort dimension captures aspects of pain more than aspects of discomfort. Potential reasons include the absence of descriptors or because pain is mentioned first in the composite item.