An analysis of the relevance of the Brief Pain Inventory interference items for measuring pain-related disability

The Brief Pain Inventory (BPI) pain interference subscale has been used as a measure of pain-related disability, a core outcome domain in the pain field. However, the pain interference subscale captures a broad range of experiences, and some items overlap with measures of distinct constructs. This overlap may inflate estimates in predictive studies and limits the precision with which treatment effects can be evaluated. To prompt reflection on appropriate use of the BPI pain interference items, this study investigated their relevance for assessing 'pain-related disability'. Participants with and without chronic pain (final sample, n=94) were presented with definitions of 'pain-related disability' and other relevant constructs, including 'pain severity', 'pain-related distress', 'depression', 'anxiety', and 'sleep disturbance'. Participants rated the degree to which items from widely used questionnaires captured the respective constructs. Linear mixed effects models examined the extent to which BPI pain interference items were rated as capturing 'pain-related disability' versus other constructs. Results indicated that the pain interference items, when considered altogether, appear to be distinct from the constructs of 'depression', 'anxiety', and 'sleep disturbance', but not from 'pain severity' and 'pain-related distress'. However, no individual item was judged to only measure 'pain-related disability' and some were judged to reflect other constructs. Although replication in a larger sample of people with pain is needed, the pain interference items capture multifaceted aspects of several constructs. Optimal use of the items requires reflection of whether they are 'fit for purpose' for the intended construct and context for which they are used. PERSPECTIVE: The Brief Pain Inventory (BPI) pain interference subscale has been used as a measure of 'pain-related disability'. BPI pain interference items do not only measure 'pain-related disability'. Appropriate use of the items requires reflection of whether they are 'fit for purpose' for the intended construct and context.