Accuracy of Identification of Cardiovascular Events with ICD Diagnosis Codes versus Physician Adjudication in CKD and Kidney Failure

Background: The risk of cardiovascular disease is elevated in individuals with chronic kidney disease (CKD), and cardiovascular disease events are common and important end-points for research studies in CKD. Adjudication by a central committee is considered the most rigorous approach of ascertaining cardiovascular disease outcomes, however, it is resource intensive. There are limited data to determine the accuracy of International Classification of Diseases (ICD) code-ascertained outcomes compared to physician-adjudication for cardiovascular disease events in CKD and kidney failure. Methods: Using data from the Chronic Renal Insufficiency Cohort, we evaluated hospitalization events in participants with CKD and kidney failure to determine accuracy of ICD-9 and 10 codes compared to physician-adjudication of the cardiovascular disease outcomes heart failure, myocardial infarction, stroke, and atrial fibrillation. For ICD codes, we determined the positive predictive value (PPV), negative predictive value (NPV), sensitivity and specificity for each cardiovascular disease outcome based on primary as well as secondary diagnosis codes. Association of known cardiovascular disease risk factors with incident cardiovascular disease outcomes were determined for ICD codes vs. physician-adjudication. Results: Comparing primary ICD-9 or 10 discharge codes to physician-adjudication, for 3464 participants, we found PPVs of 79% for heart failure, 77% for myocardial infarction, 77% for ischemic stroke, and 85% for atrial fibrillation for individuals with CKD and kidney failure. NPVs ranged from 94% to 99%. Specificities were high at 99% to 100%. Sensitivities were much lower at 15% to 48%. The associations between cardiovascular disease risk factors and co-morbidities (including age, diabetes, eGFR) were similar for ICD code-identified and physician-adjudication identified events, with r-values ranging from 0.82 to 0.98. Conclusions: PPV was near 80% for heart failure, myocardial infarction, stroke, and atrial fibrillation for primary ICD codes versus physician-adjudication, however sensitivity was lower. ICD code usage in medical research may allow greater efficiency with limited resources for outcome ascertainment.