Measuring pain in clinical trials: Pain scales, endpoints, and challenges

Abstract

Measuring pain objectively in clinical trials is a challenging task; deciding upon endpoints, selecting the tools to measure the pain, evaluation, analysis, and interpretation of data further complicates this. Though there are some guidelines available but technical and operational variations and complexities make it difficult. Since pain is a subjective dimension, an objective measurement of pain becomes highly complex. Currently, available tools for pain measurement include both uni- and multi-dimensional tools. While acute pain can be adequately measured using uni-dimensional tools, measurement of chronic pain requires multi-dimensional tool. There are several factors that may bias the measurement, analysis as well as results, and need to be considered while measuring pain in clinical trials. The present article briefly reviews the available pain assessment tools, the recommendations, issues in measurement, accuracy, validity, statistical, and interpretational challenges. We will also discuss about confounding factors while measuring pain, and how to adjust for these while analyzing the data.