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Encoding High-Dimensional Procedure Codes for Healthcare Fraud Detection

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Abstract

Machine learning applications for healthcare are reshaping the industry with new tools and services designed to improve the quality of patient care. A challenge common to many of these applications is encoding healthcare procedure codes, a high-cardinality categorical variable containing thousands of unique values. Traditional one-hot encoding techniques produce sparse binary vectors that drastically increase the size of data sets. Aggregation methods compress data to lower dimensions using summary statistics but risk forfeiting valuable information from predictive models. We compare these encoding techniques for healthcare procedure codes using two Medicare fraud classification data sets and five popular machine learning algorithms to determine how the inclusion of procedure codes affects classification performance. Next, LightGBM’s and CatBoost’s built-in methods for categorical feature handling are compared to Hcpcs2Vec embeddings, which are distributed representations of procedures that encode semantic similarities. Statistical tests show that the inclusion of the procedure code feature significantly improves performance when a one-hot representation is not used. The Hcpcs2Vec and LightGBM encoding techniques consistently perform best and second best, respectively, and outperform the one-hot and aggregate encoding methods. Feature importance measures and embedding visualizations show that the Hcpcs2Vec encodings capture key semantic qualities of procedure codes and increase the importance of the procedure code variable by an order of magnitude. These qualities make the Hcpcs2Vec procedure code embeddings appropriate for future works in healthcare.

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JMJ performed the literature review, executed the experiment design, and drafted the manuscript. TMK worked with JMJ to develop the article’s framework and focus. All authors have read and approved the final manuscript.

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Correspondence to Justin M. Johnson.

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This article is part of the topical collection “Innovative AI in Medical Applications” guest edited by Lydia Bouzar-Benlabiod, Stuart H. Rubin and Edwige Pissaloux.

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Johnson, J.M., Khoshgoftaar, T.M. Encoding High-Dimensional Procedure Codes for Healthcare Fraud Detection. SN COMPUT. SCI. 3, 362 (2022). https://doi.org/10.1007/s42979-022-01252-4

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