• Skin scarring;
  • scar scale;
  • direct magnitude estimation;
  • equal appearing interval



To determine the efficacy of interventions to improve and monitor skin scarring, a valid assessment instrument must be used. Current tools used for the evaluation of skin scarring employ equal appearing interval (EAI) scales that assume scar dimensions conform to linear models. Some scar features meet these assumptions, whereas others may not be accurately described. This study determined if current methods of scar evaluation validly characterize inherent features of scars, and in doing so, empirically validate if specific scar dimensions were best represented by linear or nonlinear mathematical models.

Study Design:

Prospective, randomized, cross-over trial.


Twenty-seven observers evaluated 30 scar photos utilizing both EAI and direct magnitude estimation (DME) scaling methods. The method of scaling and the assessed dimensions of vascularity, pigmentation, thickness, pliability, and surface area were randomized. EAI and DME data were evaluated to identify whether each scar dimension conformed to linear or curvilinear mathematical models.


Best-fit analysis revealed the dimensions of vascularity and pigmentation to be more accurately described using curvilinear functions, whereas pliability, thickness and surface area were best defined using linear models.


The scar dimension under assessment must be considered when attempting to validly apply an assessment instrument. Several commonly evaluated dimensions of skin scarring are not appropriately characterized using linear EAI scales. Thus, present assessment instruments must be revised to account for this aberration to allow for a valid means of objectively evaluating skin scarring. Laryngoscope, 2009