Key Points

International Classification of Diseases (ICD) codes had high positive predictive value compared with physician adjudication for cardiovascular events in patients with kidney disease.Sensitivities of ICD codes for cardiovascular events were lower compared with physician adjudication.ICD code usage provides opportunities for studies such as large epidemiologic studies and clinical trials, but has some limitations.

Background

The risk of cardiovascular disease is higher in individuals with 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 with physician adjudication for cardiovascular disease events in CKD and kidney failure.

Methods

Using data from the Chronic Renal Insufficiency Cohort (CRIC), we evaluated hospitalization events in participants with CKD and kidney failure to determine the accuracy of ICD-9 and 10 codes compared with 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, sensitivity, and specificity for each cardiovascular disease outcome on the basis of primary and secondary diagnosis codes. Association of known cardiovascular disease risk factors with incident cardiovascular disease outcomes was determined for ICD codes versus physician adjudication.

Results

Comparing primary ICD-9 or 10 discharge codes with 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. Negative predictive values ranged from 94% to 99%. Specificities were high at 99%–100%. Sensitivities were much lower at 15%–48%. The associations between cardiovascular disease risk factors and comorbidities (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.