The measurement of pain, 1945-2000.

Three strands of activity can be identified in the history of pain measurement. The first, psychophysics, dates back to the nineteenth century and measures the effect of analgesia by quantifying the noxious stimulation required to elicit pain, as well as the maximum stimulation tolerated. The second uses standardized questionnaires for patients, developed to categorize pain according to its emotional impact, distribution, character, and other dimensions. The third asks patients to report on pain intensity using rating scales, and is used in clinical trials where analgesics are evaluated and results can be combined to influence clinical guidelines and protocols. Although all three strands have found a place in modern clinical practice or drug development, it is the reporting of pain by patients undergoing treatment using simple scales of intensity which has emerged as the crucial method by which analgesic therapies can now be evaluated and compared.