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A Comparison of Pain Rating Scales by Sampling From Clinical Trial Data

Breivik, Else Kristine Ph.D.*; Björnsson, Gudmundur A. D.D.S.†*; Skovlund, Eva Ph.D.

The Clinical Journal of Pain: March 2000 - Volume 16 - Issue 1 - p 22-28

Objective: The goals of this study were to examine agreement and estimate differences in sensitivity between pain assessment scales.

Design: Multiple simultaneous pain assessments by patients in acute pain after oral surgery were used to compare a four-category verbal rating scale (VRS-4) and an 11-point numeric rating scale (NRS-11) with a 100-mm visual analog scale (VAS). The sensitivity of the scales (i.e., their ability [power] to detect differences between treatments) was compared in a simulation model by sampling from true pairs of observations using varying treatment differences of predetermined size.

Results: There was considerable variability in VAS scores within each VRS-4 or NRS-11 category both between patients and for repeated measures from the same patient. Simulation experiments showed that the VAS was systematically more powerful than the VRS-4 in all simulations performed. The sensitivity of the VAS and NRS-11 was approximately equal.

Conclusions: In this acute pain model, the VRS-4 was less sensitive than the VAS. The simulation results demonstrated similar sensitivity of the NRS-11 and VAS when comparing acute postoperative pain intensity. The choice between the VAS and NRS-11 can thus be based on subjective preferences.

*Department of Oral Surgery and Oral Medicine, †Section of Dental Pharmacology and Pharmacotherapy, and ‡Section of Medical Statistics, University of Oslo, Oslo, Norway

Received August 3, 1998; revised April 6, 1999; accepted October 4, 1999.

Address correspondence to Dr. E. K. Breivik, Department of Oral Surgery and Oral Medicine, University of Oslo, P.O. Box 1109 Blindern, N-0316 Oslo, Norway; e-mail:

© 2000 Lippincott Williams & Wilkins, Inc.