Comparison of Creatinine-, Cystatin C-, and Combined Creatinine–Cystatin C-Based Equations for Estimating Glomerular Filtration Rate - A Real-World Analysis in Patients with Chronic Kidney Disease

Q: How were the eGFR equations compared in the study?

eGFR was calculated using CKD-EPI 2021 creatinine-only, CKD-EPI 2012 cystatin C-only, and CKD-EPI 2021 combined creatinine–cystatin C equations, then compared across KDIGO GFR categories.

Q: How many patients showed disagreement in KDIGO GFR categorization across equations?

Out of 435 patients, 44 (10.1%) had discordant KDIGO GFR categorization depending on the equation used.

Q: Which equation showed the best clinical concordance for confirmed CKD?

The combined CKD-EPI equation demonstrated the best clinical concordance, aligning with the clinical diagnosis in all CKD cases assessed.

Sep 30, 2026

Uploaded by Taylor Morgan

Estimated glomerular filtration rate (eGFR) underpins kidney function assessment, yet CKD-EPI equations based on serum creatinine, cystatin C, or both can perform differently across clinical contexts due to non-GFR influences. A retrospective analysis of 435 adults with simultaneous creatinine and cystatin C measurements compared eGFRcr, eGFRcysC, and combined CKD-EPI 2021. Discrepant KDIGO GFR categorization occurred in 44 patients, and combined equation results matched clinical CKD in all cases, showing better concordance for diagnostic accuracy.

LanguageEnglish

CategoryHealthcare

FormatPDF

Pages12

Reading Time30 min

AccessFree to download

Abstract

1. Introduction

2. Results

2.1. Agreement and Discrepancy Among eGFR Equations

Article Comparison of Creatinine-, Cystatin C-, and Combined Creatinine–Cystatin C-Based Equations for Estimating Glomerular Filtration Rate: A Real-World Analysis in Patients with Chronic Kidney Disease Joško Osredkar 1,2, Iza Klemenˇciˇc 2, Kristina Kumer 1, Jernej Pajek 3,4 and Bojan Knap 3,4, * Academic Editor: Ligia Petrica Received: 3 December 2025 Revised: 23 December 2025 Accepted: 24 December 2025 Published: 29 December 2025 Correction Statement: This article has been republished with a minor change. The change does not affect the scientific content of the article and further details are available within the backmatter of the website version of this article. Copyright: © 2025 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license. 1 Institute of Clinical Chemistry and Biochemistry, University Medical Centre Ljubljana, Zaloška cesta 2, 1000 Ljubljana, Slovenia; [josko.osredkar@kclj.si](josko.osredkar@kclj.si) (J.O.) 2 Faculty of Pharmacy, University of Ljubljana, Aškerˇceva 7, 1000 Ljubljana, Slovenia; [iza.klemencic@gmail.com](iza.klemencic@gmail.com) 3 Department of Nephrology, Division of Internal Medicine, University Medical Centre Ljubljana, Zaloška cesta 2, 1000 Ljubljana, Slovenia; [jernej.pajek@kclj.si](jernej.pajek@kclj.si) 4 Faculty of Medicine, University of Ljubljana, Vrazov trg 2, 1000 Ljubljana, Slovenia * [Correspondence: bojan.knap@kclj.si](Correspondence: bojan.knap@kclj.si) Abstract The estimated glomerular filtration rate (eGFR) is a cornerstone of kidney function assessment. Widely used Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equations based on serum creatinine (eGFRcr ), cystatin C (eGFR cysC), or both (eGFRcr-cysC ) are influenced by non-glomerular filtration rate (GFR) factors, and their performance may vary across clinical contexts. We retrospectively analyzed 435 adult patients with simultaneous serum creatinine and cystatin C measurements. eGFR was calculated using CKD-EPI 2021 (creatinine), CKD-EPI 2012 (cystatin C), and CKD-EPI 2021 (combined) equations. Patients were classified into Kidney Disease: Improving Global Outcomes (KDIGO) GFR categories (G1–G5), and discrepancies between equations were identified. 44 patients (10.1%) showed discordant GFR categorization across all three equations and underwent detailed clinical assessment. 16 of the 44 discordant cases had clinically confirmed chronic kidney disease (CKD) . The combined equation aligned with the clinical diagnosis in all CKD cases. eGFRcr overestimated kidney function in 10/16 patients, while eGFR cysC produced lower values in 8/16, consistent with early CKD but potentially influenced by inflammation or obesity. Reclassification occurred in 9/16 patients when switching fromeGFRcr to eGFRcr-cysC, including four who shifted from G2 to G3a–G4 . A significant difference was observed between eGFRcr and eGFRcr-cysC (p < 0.05) . The combined CKD-EPI equation demonstrated the best clinical concordance, supporting its broader use when diagnostic accuracy is essential. Keywords: chronic kidney disease; glomerular filtration rate; eGFR; CKD-EPI; creatinine; cystatin C; GFR classification; diagnostic accuracy 1. Introduction Chronic kidney disease (CKD) is a growing global health concern, affecting over 850 million individuals worldwide and associated with significantly increased cardiovascular morbidity, mortality, and health care costs [1–4]. Early identification and accurate staging of CKD are essential for optimizing management, adjusting nephrotoxic or renally-excreted medications, and improving patient outcomes. The glomerular filtration rate (GFR) is widely accepted as the best overall indicator of kidney function, yet its direct measurement (mGFR) using exogenous filtration markers (e.g., inulin, iohexol) or measured creatinine clearance (requiri

FAQs

How were the eGFR equations compared in the study?

eGFR was calculated using CKD-EPI 2021 creatinine-only, CKD-EPI 2012 cystatin C-only, and CKD-EPI 2021 combined creatinine–cystatin C equations, then compared across KDIGO GFR categories.

How many patients showed disagreement in KDIGO GFR categorization across equations?

Out of 435 patients, 44 (10.1%) had discordant KDIGO GFR categorization depending on the equation used.

Which equation showed the best clinical concordance for confirmed CKD?

The combined CKD-EPI equation demonstrated the best clinical concordance, aligning with the clinical diagnosis in all CKD cases assessed.

Sep 30, 2026

Uploaded by Taylor Morgan