Have ICD-10 Coding Practices Changed Since 2015?

Usage of ICD-10 codes in administrative data has continued to shift since mandatory adoption in 2015. Identifying changing patterns in coding behavior is imperative in producing reliable analyses and robust conclusions. We examined the granularity of ICD-10 coding over time in a cohort selected from the IBM Explorys Therapeutic Dataset, which contains the records of over 60 million patients. Our seasonality-aware trend model identified patterns of interest, such as increased use of laterality codes for pain and increased use of codes denoting concepts novel to ICD- 10 for screening encounters. Those relying on these codes should adjust for these 'learning curve' effects. This work should be extended to additional modalities of terminology usage and represents a starting point for researchers working with dynamic clinical ontologies.