Comparative Evaluation of Creatinine- and Cystatin C-Based eGFR Equations in Patients with Ischemic Heart Disease: Implications for Renal Risk Stratification

Open Access

Abstract

Background: Renal dysfunction is a common but frequently underrecognized comorbidity in patients with ischemic heart disease (IHD). Accurate estimation of glomerular filtration rate (eGFR) is essential for early identification of chronic kidney disease (CKD), cardiovascular risk stratification, and clinical management. Creatinine-based equations may underestimate renal impairment in cardiovascular patients, whereas cystatin C-based equations may provide greater sensitivity. Aim of the study: To compare creatinine- and cystatin C-based eGFR equations in patients with ischemic heart disease and evaluate their effectiveness in renal risk stratification. Methods & Materials: This cross-sectional comparative study was conducted in the Department of Nephrology at Sir Salimullah Medical College and Mitford Hospital from July 2020 to June 2021. A total of 234 participants were enrolled, including 194 patients with diagnosed ischemic heart disease and 40 healthy controls. Renal function was assessed using MDRD, CKD-EPIcr, CKD-EPIcys, and CKD-EPIcr-cys equations. Creatinine- and cystatin C-based equations were compared regarding CKD staging, renal dysfunction detection, and risk reclassification. Statistical analyses included chi-square test, Student's t-test, Friedman test, kappa statistics, and multivariable logistic regression. Result: Mean serum creatinine and cystatin C levels were significantly higher in IHD patients than controls, while all eGFR estimates were significantly lower (p<0.001). Cystatin C-based equations showed significantly lower mean eGFR values than creatinine-based equations (57.1±24.7 vs. 66.7±29.1 mL/min/1.73m², p=0.001). Renal dysfunction (eGFR <60 mL/min/1.73m²) was detected in 52.1% of patients using cystatin C-based equations compared with 38.1% using creatinine-based equations. CKD-EPIcys newly identified CKD in 24.7% of patients and reclassified 22.2% into higher CKD stages. The strongest agreement was observed between MDRD and CKD-EPIcr (κ=0.819), while weak agreement existed between CKD-EPIcr and CKD-EPIcys (κ=0.199). Age >60 years, hypertension, diabetes mellitus, smoking, elevated serum creatinine, and elevated cystatin C were significant predictors of renal dysfunction. Conclusion: Cystatin C-based eGFR equations identified substantially more renal dysfunction and higher CKD stages among patients with ischemic heart disease compared with creatinine-based equations. These findings suggest that cystatin C-based assessment may improve early detection of renal impairment and enhance renal risk stratification in cardiovascular patients.