Abstract
Abstract Introduction The Visual Analogue Scale (VAS), Numeric Rating Scale (NRS), Verbal descriptor scale, and faces pain scale are used to measure postoperative pain in adults. However, their utility in this population has not been reviewed systematically. We aimed to summarise and appraise the evidence relating to the measurement properties of unidimensional tools when used for this population and to identify available tools assessing the impact of pain on the restoration of function. Method Four databases (MEDLINE, EMBASE, CINAHL, PsycINFO) were searched up to August 2020 for relevant studies. Two reviewers independently screened articles and assessed risk of bias using the COensus-based Standards for the selection of health Measurement Instruments (COSMIN) checklist. Result Thirty-one studies were included. Only one study included an objective pain score; a tool assessing pain interference with function and reported low-quality evidence for construct validity. Studies looked at unidimensional tools were underpinned by low or very low-quality evidence for reliability, and all displayed a low quality of evidence of indeterminate responsiveness. Measurement error was only reported for VAS in one study of moderate quality. Interpretability results were available only for VAS and NRS. Feasibility results varied based on the included population. Conclusion Despite the extensive use of unidimensional tools, there is no evidence to suggest that any of these tools has superior measurement properties for postoperative pain. Therefore, future studies should be prioritised to assess their validity, measurement error and responsiveness. Validation studies of pain assessment tools that promote function are needed. Take-home Message Take home message: Functional pain scores should be assessed and validated for postoperative pain.