Although the verbal numeric scale (VNS) is used frequently at patients' bedsides, it has never been formally validated in children with acute pain. In order to validate this scale, a prospective cohort study was performed in children between 8 and 17years presenting to a pediatric emergency department (ED) with acute pain. Pain was graded using the VNS, the visual analogue scale (VAS), and the verbal rating scale (VRS). A second assessment was done before discharge. We determined a priori that in order to be valid, the VNS would need to: correlate with the VAS (concurrent validity); decrease after intervention to reduce pain (construct validity); and be associated with the VRS categories (content validity). The VNS interchangeability with the VAS, its minimal clinically significant difference, and test-retest reliability were also determined. A total of 202 patients (mean age: 12.2+/-2.6years) were enrolled. The VNS correlated with the VAS: r(ic)=0.93, p<0.001. There were differences in the VNS before versus after interventions (p<0.001), and between VRS categories (mild versus moderate, p<0.001; moderate versus severe, p<0.001). The 95% limits of agreement (interchangeability) between VNS/VAS were outside the a priori set limit of +/-2.0: -1.8, 2.5. The VNS minimal clinically significant difference was 1. The VNS had good test-retest reliability with 95% limits of agreement of -0.9 and 1.2. In conclusion, the VNS provides a valid and reliable scale to evaluate acute pain in children aged 8-17years but is not interchangeable with the VAS.
Copyright 2009 International Association for the Study of Pain. Published by Elsevier B.V. All rights reserved.