Pain measurement tools for clinical practice and research.

An important component of effective postoperative pain management is a measure of the patient's pain intensity. This article examines three unidimensional pain measurement instruments and one multidimensional pain measurement instrument used in daily practice and clinical research. The strengths and weaknesses of the numerical rating scale, verbal descriptor scale, visual analogue scale, and the McGill Pain Questionnaire are discussed. Issues of validity and reliability, important in clinical research, are also presented.