Reliability of Three-Dimensional Facial Landmarks Using Multivariate Intraclass Correlation

The intraclass correlation coefficient (ICC) is widely used in many fields, including orthodontics, as a measure of reliability of quantitative data. The main goals of this study were to determine the multivariate intraclass correlation, a measure of intra-rater reliability, for the selection of 6 3D mid-facial soft tissue landmarks and compare the multivariate ICC with other measures of landmark reliability. 3D stereophotogrammetric images of 15 randomly selected subjects were landmarked twice by the same rater using 3dMD software. The multivariate ICC was found to be as high or higher than the individual coordinate measures in each of the landmarks examined in this study. The reliability of all six soft-tissue landmarks in this study was excellent (ICC >0.98). When the within-coordinate and Euclidean distance criteria were applied, the reliability of the landmarks was found to be acceptable. However, the two selections of the landmark pronasion were found to be significantly different in the X coordinate. The multivariate ICC identified this same landmark as its lowest estimate of ICC. This indicates that the multivariate ICC may be important in quantifying reliability and warrants investigation in future craniofacial landmark reliability studies. Introduction The intraclass correlation coefficient is widely used in many fields, including orthodontics, as a measure of reliability of quantitative data. With the availability of technical software capable of