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A comparison of pain rating scales by sampling from clinical trial data
E K Breivik1, G A Björnsson, E Skovlund
1Department of Oral Surgery and Oral Medicine, University of Oslo, Norway. ekristin@udont.uio.no
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.