Objective: To compare 2 clinical wound scales and to determine a minimal clinically important difference (MCID) on the visual analog cosmesis scale.
Methods: Using data from 2 previously published clinical trials, 91 lacerations and 43 surgical incisions were assessed on the 2 scales; a 100-mm visual analog scale (VAS) (0 = worst possible scar, 100 = best possible scar) and a wound evaluation scale (WES) assessing 6 clinical variables (a score of 6 is considered optimal, while a score of < or =5 suboptimal). All wound assessments on the VAS were done by 2 cosmetic surgeons who rated photographs on 2 occasions. A cohort of wounds on the WES were assessed by a second observer. The difference of the mean optimal and suboptimal VAS scores for each study was used to determine a MCID on the VAS scale.
Results: The VAS scale yielded intraobserver agreements of 0.93 and 0.87 (95% CI: 0.89-0.96 and 0.78-0.93) and interobserver agreements of 0.50 and 0.71 (95% CI: 0.32-0.65 and 0.52-0.84) for lacerations and incisions, respectively. Kappa coefficient measuring agreement on the WES was 0.79 (95% CI: 0.57-1.0). The mean (+/-SD) VAS scores of optimal wounds were 72 +/- 12 mm and 65 +/- 20 mm, while the mean scores of suboptimal wounds were 57 +/- 17 mm and 50 +/- 23 mm for lacerations and incisions, respectively.
Conclusions: An MCID on the VAS cosmesis scale is 15 mm. Studies should be designed to have a sample size and power to detect this difference.