Carpals and epiphyses of radius and ulna as age indicators using longitudinal data: a Bayesian approach

The aim of this study is to develop a new formula for age estimation in a longitudinal study of a sample from the radiological collection of wrist bones of growing infants, children, and adolescents recorded at the Burlington Growth Centre. A sample of 82 individuals (43 boys and 39 girls), aged between 3 and 16 years, were analyzed with a total of 623 X-rays of left hand-wrist bones by measuring the area of carpal bones and epiphyses of the ulna and radius (Bo) and carpal area (Ca). The intra-class correlation coefficient (ICC) and its 95% confidence interval were used to evaluate intra-observer agreement. Hierarchical Bayesian calibration has been adopted to exceed the bias deriving from the classical regression approach used for age estimation in forensic disciplines, since it tends to overestimate or underestimate the age of the individuals. Calibration distributions of the dataset obtained by the evaluation of BoCa (the ratio of Bo and Ca) suggested mean absolute errors (MAE) of 1.07 and 1.34 years in boys and girls, respectively. The mean interquartile range (MIQR) was 1.7 and 2.42 years in boys and girls, respectively. The respective bias of the estimates was β_ERR = - 0.025 and - 0.074. Furthermore, a correspondence between different BoCa values and estimated age with its standard deviation (SD) was calculated for boys and girls, respectively. In conclusion, the Bayesian calibration method appears to be suitable for assessing both age and its distribution in subadults, according to hand-wrist maturity. Furthermore, it can easily incorporate other age predictors, obtaining a distribution of the subjects with multivariate predictors.