Has ICD-10 improved identification of rapidly progressing stage 3 and stage 4 chronic kidney disease patients: A diagnostic test study

Abstract

Abstract Background: The International Classification of Diseases (ICD) coding system is the industry standard tool for billing, disease classification, and epidemiology purposes. Prior research has demonstrated ICD codes to have poor clinical and diagnostic accuracy, particularly in relation to chronic kidney disease (CKD). In 2016, the ICD system moved from revision 9 to revision 10. This study examines the accuracy of ICD-10 CKD-staging codes in diagnosing clinically identified CKD patients in a large insurer database. Patients and methods: Serial observations of outpatient serum creatinine measurements collected from 2016 through 2021 of 315,903 patients were transformed to estimated glomerular filtration rate (eGFR) to identify CKD stage-3 and advanced patients diagnosed clinically (eGFR-CKD). CKD-staging codes from the same time period of 59,386 patients and used to identify stage-3 and advanced patients diagnosed by ICD-code (ICD-CKD). eGFR-CKD and ICD-CKD diagnostic accuracy was compared between a total of 334,610 patients. Results: 34,858 patients were diagnosed as eGFR-CKD stage-3 patients, of which 17,549 were also diagnosed as ICD-CKD stage-3 patients, for a sensitivity of 50.34%, specificity of 95.88%, positive predictive value (PPV) of 58.71%, and negative predictive value (NPV) of 94.32%. 4,069 patients reached eGFR-CKD stage-4 with 2,750 ICD-CKD stage-4 patients, giving a sensitivity of 67.58%, specificity of 98.87%, PPV of 42.43%, and NPV of 99.60%. 959 patients reached eGFR-CKD stage-5 with 566 ICD-CKD stage-5 patients, giving a sensitivity of 59.02%, specificity of 99.7%, PPV of 35.85%, and NPV of 99.88%. Conclusion: This research shows that the recent ICD coding revision has offered some improvement in diagnostic accuracy, with marked increases in sensitivity for stage-3 (50.34% vs. 24.68%), and PPV in stage-3 (58.71% vs. 40.08%), stage-4 (42.43% vs. 18.52%), and stage-5 (35.85% vs. 4.51%). However, sensitivity in stage-5 compares poorly (59.02% vs. 91.05%). Keywords: progression, CKD, ICD, sensitivity, specificity