Assessing pain in persons with opioid use disorder: Approaches, techniques and special considerations.

Pain and opioid use disorder (OUD) are inextricably linked, as the former can be a risk factor for the development of the latter, and over a third of persons with OUD suffer concomitant chronic pain. Assessing pain among people with OUD is challenging, because ongoing opioid use brings changes in pain responses and most pain assessment tools have not been validated for this population. In this narrative review, we discuss the fundamentals of pain assessment for populations with OUD. First, we describe the biological, psychological and social aspects of the pain experience among people with OUD, as well as how opioid-related phenomena may contribute to the pain experience in this population. We then review methods to assess pain, including (1) traditional self-reported methods, such visual analogue scales and structured questionnaires; (2) behavioural observations and physiological indicators; (3) and laboratory-based approaches, such as quantitative sensory testing. These methods are considered from a perspective that encompasses both pain and OUD. Finally, we discuss strategies for improving pain assessment in persons with OUD and implications for future research, including educational strategies for multidisciplinary teams. We highlight the substantial gaps that persist in this literature, particularly regarding the applicability of current pain assessment methods to persons with OUD, as well as the generalizability of the existing results from adjacent populations on chronic opioid therapy but without OUD. As research linking pain and OUD evolves, considering the needs of diverse populations with complex psychosocial backgrounds, clinicians will be better equipped to reduce these gaps.