Standardizing ordinal subadult age indicators: Testing for observer agreement and consistency across modalities

Skeletal and dental data for subadult analyses obtained from dry bones or various types of medical images, such as computed tomography (CT) scans or conventional radiographs/x-rays, should be consistent and repeatable to ensure method applicability across modalities and support combining study samples. The present study evaluates observer agreement of epiphyseal fusion and dental development stages obtained on CT scans of a U.S. sample and the consistency of epiphyseal fusion stages between CT scans and projected scan radiographs/scout images (U.S. CT sample), and between dry bones and conventional x-rays (Colombian osteological sample). Results show that both intra- and interobserver agreements of scores on CT scans were high (intra: mean Cohen's kappa=0.757-0.939, inter: mean Cohen's kappa=0.773-0.836). Agreements were lower for dental data (intra: mean Cohen's kappa=0.757, inter: mean Cohen's kappa=0.773-0.0.820) compared to epiphyseal fusion data (intra: mean Cohen's kappa=0.939, inter: mean Cohen's kappa=0.807-0.836). Consistency of epiphyseal fusion stages was higher between dry bones and conventional x-rays than between CT scans and scout images (mean Cohen's kappa=0.708-0.824 and 0.726-0.738, respectively). Differences rarely surpassed a one-stage value between observers or modalities. The complexity of some ossification patterns and superimposition had a greater negative impact on agreement and consistency rates than observer experience. Results suggest ordinal subadult skeletal data can be collected and combined across modalities.