The Discrepancy Between Estimated GFR Cystatin C and Estimated GFR Creatinine at 3 Months After Hospitalization and Long-Term Adverse Outcomes

Introduction: The prognostic value of the discrepancy between the estimated glomerular filtration rate (eGFR) using cystatin C (eGFRcys) and creatinine (eGFRcr) in recently hospitalized adults remains poorly understood. Methods: We characterized the difference between eGFRcys and eGFRcr, at 3 months after discharge, in 1534 hospitalized adults; 767 (50%) with acute kidney injury (AKI) matched 1:1 with patients who did not develop AKI. We used survival analysis to determine the associations between having lower eGFRcys than eGFRcr with risk of end-stage kidney disease (ESKD), major atherosclerotic cardiac events (MACE), heart failure hospitalization, and death after a a median follow-up of 4.7 years. Results: The mean age of study participants was 65.8 years, and 37.3% were female. At 3 months after hospitalization, the median (interquartile range [IQR]) eGFRcr and eGFRcys were 71.5 (51.9–92.6) and 50.5 (34.1–71.9) ml/min per 1.73 m², respectively, with a median (IQR) absolute difference of −16.3 (−26.1 to −6.3) ml/min per 1.73 m² and percent difference of −26% (−39% to −11%). The presence of eGFRcys at least 30% lower than eGFRcr at 3 months was associated with a higher risk of heart failure hospitalization (adjusted hazard ratio [aHR]: 1.41, 95% confidence interval [CI]: 1.06–1.89), ESKD (aHR: 1.95, 95% CI: 1.02–3.72), and death (aHR: 2.09, 95% CI: 1.64–2.67), and these associations were consistent in participants with and without AKI (P for interaction with AKI all > 0.1). Conclusion: Our findings suggest that the eGFRcys-eGFRcr discrepancy may serve as a valuable prognostic marker in recently hospitalized patients, informing risk stratification and potential interventions.