Validation of Bone Age Methods by Their Ability to Predict Adult Height

Abstract

Aim: Several bone age (BA) methods are in use today. The aim of this study was to introduce a framework for assessing the validity of a BA method by its ability to predict adult height (H) and to apply it to manual ratings based on Greulich-Pyle (GP) and Tanner-Whitehouse 3 (TW) and to the fully automated BoneXpert method. Material: The study used X-rays of 232 children from the First Zurich Longitudinal Study recorded close to each anniversary. Method: For each height measurement (h), we calculated the growth potential (gp), defined as gp = (H – h)/H. The standard deviation of the gp prediction error for children of the same age was taken as a measure of the validity of the BA method and averaged over the age range 10–18 years for boys and 8–16 years for girls to obtain the overall gp prediction error (GPPE). Results: Manual TW yielded GPPE = 1.32% [95% CI 1.28–1.36], and was significantly outperformed by manual GP with GPPE = 1.26% [1.22–1.30]. The automated rating obtained GPPE = 1.23%, and omitting radius and ulna yielded GPPE = 1.22%. Conclusion: Manual GP rating is better than manual TW rating in predicting adult height, and the fully automated method works as well as manual GP rating.