Validation and reference values of automated bone age determination for four ethnicities.

RATIONALE AND
OBJECTIVES: Bone age (BA) rating is associated with a considerable rater variability, which would be eliminated with an automated computerized method. The aim of the study was to validate the BoneXpert method, an automated determination of BA, in American children of four ethnicities.
MATERIALS AND METHODS: The study is based on a publicly available database of hand x-rays of healthy children, established in a previous, National Institutes of Health-funded study. Radiographs of the left hand were recorded between 1993 and 2006 in Los Angeles, including 1100 images with two independent manual BA ratings and 280 additional images for which the manual ratings were not used. Images were evenly split between Caucasian, African American, Hispanic, and Asian children, and the age range was 0-18.99 years.
RESULTS: The automated method analyzed all images with BA >2.5 years for boys and >2 years for girls. The root-mean-square (RMS) error between the two manual ratings was 0.63 years, whereas the RMS deviation between the automated BA and the average of the two manual ratings was 0.61 years. The mean BA minus age was computed versus age for each sex and ethnicity. The largest deviation from zero was seen for Hispanic and Asian children older than 12 years, who were about 1 year advanced relative to the Greulich and Pyle standard.
CONCLUSION: The automated method can analyze images of all ethnicities within a BA range of 2.5-17 years for boys and 2-15 years for girls, and can therefore eliminate the problem with rater variability in BA rating.