Epidemiologic Method Review at Scale: Assessing Charlson Comorbidity Versioning Using a Large Language Model

The Charlson Comorbidity Index (CCI) is widely used in epidemiologic studies. However, many versions of the CCI have been developed since the original method was published in 1987, and it is unclear which version is used most frequently and how version utilization in research has changed over time. We present an approach using a large language model to extract data from articles by detecting which specific CCI version is employed. We analyzed 31,767 articles published since 2012 to evaluate the landscape of CCI implementation. We show that 63% of articles that cite a single method version cite only the original CCI publication, which cannot be applied in the modern real-world data era, leading to ambiguity in actual CCI implementation. More generally, this paper introduces a generalizable approach to scaling methods literature review beyond typical human-review, which we validate and demonstrate through application to the CCI.