A clinimetric assessment of the validity and reliability of 3D technology for scar surface area measurement

The quality of scars has become an important outcome of burn care. Objective scar assessment through scar surface area measurement enables quantification of scar formation and evaluation of treatment efficacy. 3D technology has proven valid and reliable but often remains cumbersome, expensive, and time-consuming. 3D technology with depth sensors on mobile devices has become available and might surpass these limitations. This study provides a clinimetric assessment of the validity and reliability of a 3D system with a depth sensor for scar surface area measurement. A technology involving a depth sensor mounted on a mobile device was used. Images and analyses were made with a custom-made software application. A standardized one-keyframe image capturing procedure was followed. To assess validity, stickers with predefined dimensions (8.01 cm2 – 77.70 cm2) were imaged in a single observer setting on various body parts of healthy volunteers. To assess reliability, hypertrophic scars, keloids, and normotrophic scars were imaged and rated by two observers independently. Data are expressed as mean (+/-SD), Coefficient of Variation (CV), Intraclass Correlation Coefficients (ICC), and Limits of Agreements (LoA). Eighty stickers placed on 20 healthy volunteers showed validity with CV between 0.62%− 1.67% for observer A and 0.75%− 1.19% for observer B. For the reliability study, 69 scars on 36 patients were included. Mean scar surface area ranged from 0.83 cm2 to 155.59 cm2. Mean scar surface area measurement was 13.83 cm2 (SD 23.06) for observer A and 13.59 cm2 (SD 23.31) for observer B. Adjusted interobserver CV for trained observers is estimated as 5.59%, with corresponding LoA = 0 ± 0.15 x mean surface area. Interobserver ICCs were 0.99–1.00. This 3D technology with a depth sensor for measuring scar surface area provides valid and reliable data and thereby surpasses expensive and time-consuming 3D cameras. •Mobile 3D technology provides valid and reliable scar surface area measurements.•Mobile 3D technology surpasses other expensive and cumbersome 3D cameras.•Mobile applications provide instant scar data and evaluation for clinical use.•3D mobile applications are feasible for daily practice.