Pain as outcome variable in clinical trials - what reduction in pain is relevant to the patient?

Background and Methods: Ninety-eight postoperative patients were asked to i ndicate their actual pain levels on a 100 mm visual analogue scale. One hou r later, the measurements were repeated, and the patients were asked whethe r their pain had become better, worse or was unchanged. We plotted receiver -operating-characteristics (ROC) curves to determine the VAS's sensitivity to changes. Results: A reduction resp. increase of pain levels of 5 resp. 4 mm was foun d to be perceivable. Sensitivity and specificity was around 80% for both re sults. Conclusion: The VAS is a highly sensitive tool for pain intensity measureme nts. Its use enables surgeons to detect even minimal, but patient-relevant changes in pain intensity.