Chronic kidney disease and prognosis in elderly patients with cardiovascular disease: Comparison between CKD-EPI and Berlin Initiative Study-1 formulas

BACKGROUND: Chronic kidney disease (CKD) is frequent in patients with cardiovascular (CV) disease and impacts prognosis in these subjects. While current guidelines recommend the CKD-EPI equation for the estimated glomerular filtration rate (eGFR) and recognizing CKD, a new creatinine-based equation - the Berlin Initiative Study-1 (BIS-1) - was generated for elders with a high prevalence of CV disease. We assessed whether BIS-1 provided more accurate risk stratification than the CKD-EPI equation in unselected aged patients with CV disease. METHODS: Patients aged ≥70 years who were seen consecutively at the Cardiovascular Centre of Trieste (Italy) between November 2009 and October 2013 were recruited into this study. The correlation and agreement between the BIS-1 and CKD-EPI formulas were evaluated and intra-class correlation coefficients (ICCs) were computed in order to estimate the correlation between the two formulas. Patients were followed for all-cause death, composite outcomes of all-cause death/all-cause hospitalization and all-cause death/CV hospitalization. RESULTS: A total of 7845 subjects met the inclusion criteria for this study. GFR as estimated with the BIS-1 and the CKD-EPI equation was highly correlated (ICC: 0.81; 95% confidence interval [CI]: 0.79-0.82; p < 0.0001). When allocating patients in Kidney Disease Improving Global Outcomes classes of eGFR, compared to CKD-EPI, the BIS-1 formula reclassified 2720 (34.7%) patients: 53 (1.9%) were placed in a better class and 2667 (98.1%) were placed in a worse class. Multivariable Cox models showed that BIS-1 compared to CKD-EPI had a significantly better accuracy for predicting death (NRI: 0.12; 95% CI: 0.03-0.19; p = 0.001), death/CV hospitalization (net reclassification improvement [NRI]: 0.34; 95% CI: 0.27-0.38; p < 0.001) and death/all-cause hospitalization (NRI: 0.14; 95% CI: 0.06-0.21; p = 0.001). CONCLUSIONS: The BIS-1 formula is better than the CKD-EPI formula for risk stratification of CKD in elderly people with CV disease.