{"doi":"10.1097/01.mlr.0000182534.19832.83","title":"Coding Algorithms for Defining Comorbidities in ICD-9-CM and ICD-10 Administrative Data","abstract":"<h4>Objectives</h4>Implementation of the International Statistical Classification of Disease and Related Health Problems, 10th Revision (ICD-10) coding system presents challenges for using administrative data. Recognizing this, we conducted a multistep process to develop ICD-10 coding algorithms to define Charlson and Elixhauser comorbidities in administrative data and assess the performance of the resulting algorithms.<h4>Methods</h4>ICD-10 coding algorithms were developed by \"translation\" of the ICD-9-CM codes constituting Deyo's (for Charlson comorbidities) and Elixhauser's coding algorithms and by physicians' assessment of the face-validity of selected ICD-10 codes. The process of carefully developing ICD-10 algorithms also produced modified and enhanced ICD-9-CM coding algorithms for the Charlson and Elixhauser comorbidities. We then used data on in-patients aged 18 years and older in ICD-9-CM and ICD-10 administrative hospital discharge data from a Canadian health region to assess the comorbidity frequencies and mortality prediction achieved by the original ICD-9-CM algorithms, the enhanced ICD-9-CM algorithms, and the new ICD-10 coding algorithms.<h4>Results</h4>Among 56,585 patients in the ICD-9-CM data and 58,805 patients in the ICD-10 data, frequencies of the 17 Charlson comorbidities and the 30 Elixhauser comorbidities remained generally similar across algorithms. The new ICD-10 and enhanced ICD-9-CM coding algorithms either matched or outperformed the original Deyo and Elixhauser ICD-9-CM coding algorithms in predicting in-hospital mortality. The C-statistic was 0.842 for Deyo's ICD-9-CM coding algorithm, 0.860 for the ICD-10 coding algorithm, and 0.859 for the enhanced ICD-9-CM coding algorithm, 0.868 for the original Elixhauser ICD-9-CM coding algorithm, 0.870 for the ICD-10 coding algorithm and 0.878 for the enhanced ICD-9-CM coding algorithm.<h4>Conclusions</h4>These newly developed ICD-10 and ICD-9-CM comorbidity coding algorithms produce similar estimates of comorbidity prevalence in administrative data, and may outperform existing ICD-9-CM coding algorithms.","journal":"Medical Care","year":2005,"id":3725,"datarank":28.240958516843456,"base_score":9.261793653565098,"endowment":9.261793653565098,"self_citation_contribution":1.389269048034765,"citation_network_contribution":26.85168946880869,"self_endowment_contribution":1.389269048034765,"citer_contribution":26.85168946880869,"corpus_percentile":98.5,"corpus_rank":893,"citation_count":10527,"citer_count":191,"citers_with_citation_signal":191,"citers_with_endowment":191,"datacite_reuse_total":0,"is_dataset":false,"is_oa":false,"file_count":0,"downloads":0,"has_version_chain":false,"published_date":"2005-11-01","authors":[{"id":37819,"name":"Vijaya Sundararajan","orcid":"0000-0001-9387-1865","position":1,"is_corresponding":false},{"id":37820,"name":"Patricia Halfon","orcid":null,"position":2,"is_corresponding":false},{"id":37821,"name":"Andrew Fong","orcid":"0000-0003-3436-7751","position":3,"is_corresponding":false},{"id":37822,"name":"Bernard Burnand","orcid":"0000-0002-5678-6044","position":4,"is_corresponding":false},{"id":37823,"name":"Jean-Christophe Luthi","orcid":null,"position":5,"is_corresponding":false},{"id":37824,"name":"L. Duncan Saunders","orcid":null,"position":6,"is_corresponding":false},{"id":37825,"name":"Cynthia A. Beck","orcid":null,"position":7,"is_corresponding":false},{"id":37826,"name":"Thomas E. Feasby","orcid":null,"position":8,"is_corresponding":false},{"id":37827,"name":"William A. Ghali","orcid":null,"position":9,"is_corresponding":false},{"id":37828,"name":"Jean‐Christophe Luthi","orcid":null,"position":10,"is_corresponding":false},{"id":37818,"name":"Hude Quan","orcid":"0000-0002-7848-7256","position":0,"is_corresponding":true}],"reference_count":20,"raw_metadata":{"citation_network_status":"fetched"},"created_at":"2026-03-01T18:20:47.508186Z","pmid":null,"pmcid":null,"fwci":null,"citation_percentile":null,"influential_citations":0,"oa_status":null,"license":null,"views":0,"total_file_size_bytes":0,"version_count":0,"clinical_trials":[],"software_tools":[],"db_accessions":[],"linked_datasets":[],"topics":[]}