Reliability and Photographic Equivalency of the Scar Cosmesis Assessment and Rating (SCAR) Scale, an Outcome Measure for Postoperative Scars

Importance: Until recently, no ideal valid, feasible, and reliable scar scale existed to effectively assess the quality of postoperative linear scars. The Scar Cosmesis Assessment and Rating (SCAR) scale was developed and validated as a tool to assess the quality of postoperative scars in clinical and research settings. Objective: To assess the reliability of using photographs in lieu of live patient scar rating assessments, and to determine the interrater and intrarater reliability of the SCAR scale. Design, Setting, and Participants: This was a reliability study to assess clinicians' interrater and intrarater reliability, as well as the reliability of using high-quality macrophotographs of postoperative scars. Patients were from a private practice dermatology clinic, with assessed scars representing a range of surgical procedures including those performed by dermatologists, plastic surgeons, and general surgeons. Assessments were performed by an international multidisciplinary team from dermatology, plastic surgery, surgical oncology, emergency medicine, and physiatry, using photographs and live patient assessments. A single photograph was assessed for each patient's scar. Data were obtained between August 3, 2015, and January 18, 2016. Data analysis occurred between January 18, 2016, and July 29, 2016. Using the intraclass correlation coefficient (ICC), the scale was tested for photographic equivalency as well as interrater reliability and intrarater reliability by 5 raters on a set of 80 total patient scars, 20 of which were analyzed for photographic equivalency and the remaining 60 of which were analyzed for interrater and intrarater reliability. Main Outcomes and Measures: The SCAR scale that measures postoperative scar cosmesis, with scores ranging from 0 (best possible scar) to 15 (worst possible scar), based on 6 clinician and 2 patient items was used. Of those 60 in the photographic subgroup, 10 were rated using not only the SCAR scale but also the Patient and Observer Scar Assessment Scale and the Vancouver Scar Scale, and 10 were assessed twice by the same rater at different times to assess intrarater reliability. Results: Patients' ages ranged from 18 to 96 years, with Fitzpatrick skin types I through VI. Thirty-seven were male, and 43 were female. A set of 20 live patient scars with associated photographs, as well as a separate set of 60 photographs, were rated; 10 patients were assessed twice for intrarater reliability. The SCAR scale ratings using photographs were found to be largely equivalent to live patient assessments, with ICCs of 0.99 (95% CI, 0.96-0.99) and 0.98 (95% CI, 0.96-0.99). The interrater reliability of the overall scale showed an ICC of 0.95 (95% CI, 0.96-0.99) using a 2-sample random-effects model. Intrarater reliability found ICCs ranging from 0.96 to 0.99 with 5 separate raters. Modeling the overall SCAR score predicted whether the rater would consider the scar undesirable, with an odds ratio of association of 1.76 (95% CI, 1.24-2.2). A secondary analysis of Fitzpatrick skin types IV, VI, and VI demonstrated a sustained interrater reliability, with an ICC of 0.93 (95% CI, 0.86-0.98). Conclusions and Relevance: The SCAR scale is a reliable rating scale for postoperative linear scars, and photographs may reliably be used in lieu of live patient assessments. The SCAR scale therefore represents a reliable standard rating scale for postoperative scar cosmesis.