Preferred Presentation of the Visual Analog Scale for Measurement of Postoperative Pain.

Abstract

The aim of this study was to evaluate differences in pain scores with different visual analog scale (VAS) presentations and to compare those differences with a numeric rating scale. We also asked the patients for preference of the different methods. Prior to the trial, we performed power calculations to estimate a preferred sample size, and 62 postoperative patients supplied a complete set of data to the study. Inclusion criteria were newly operated patients within the first 5days after surgery. Every patient included was with 1-minute intervals and presented with one of the following 100-mm VAS lines: VAS horizontal with or without stop lines at the endings, or VAS vertical with or without stop lines. They also completed a numeric rating scale (NRS). We did not find differences in pain scores between the four VAS measures. The NRS had slightly higher pain scores than VAS, especially at low levels of pain. Patients preferred the NRS as compared to the VAS, and when choosing between the four different VAS presentations, they preferred the horizontal VAS with stop lines at the ends. For daily clinical practice for guiding postoperative analgesic treatment, the NRS seems to be a good option measuring pain reliably with good patient understanding and acceptance. For pain research, where there may be more time to explain the method and when a scale with more data points may be preferred, a VAS horizontal including stop lines at the ends can be recommended.