Measurement of pain

Clinical investigators have recognized the varieties of pain experience; however, until recently, the methods used for pain measurement treated pain as though it were a single, unique quality that varies only in intensity. Approaches to pain measurement include verbal and numeric self-rating scales, behavioral observation scales, and scales that measure physiologic responses. The complex nature of pain suggests that these diverse measurements may not always show high concordance. Because pain is subjective, the patient's self-report provides the most valid measure of the experience, especially when concordance is low. The most frequently used self-rating instruments for pain measurement in clinical and research settings are the Visual Analog Scale and the McGill Pain Questionnaire. The McGill Pain Questionnaire was designed to assess the multidimensional nature of pain experience, and has been shown to be a reliable, valid, and consistent measurement tool. A short-form McGill Pain Questionnaire is available for specific research settings when the time to obtain information from patients is limited and when more information than simply the intensity of pain is desired. Further development and refinement of pain measurement techniques will lead to increasingly accurate tools that have more predictive powers.