Elsevier

Clinical Biochemistry

Volume 45, Issue 18, December 2012, Pages 1694-1696
Clinical Biochemistry

Case Report
Estimating glomerular filtration rate (GFR) in diabetes: The performance of MDRD and CKD-EPI equations in patients with various degrees of albuminuria

https://doi.org/10.1016/j.clinbiochem.2012.07.115Get rights and content

Abstract

Objectives

The aim of this study was to compare the performance of Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) and Modification of Diet in Renal Disease Study (MDRD) equations in estimating GFR in a large cohort of diabetic patients with various degrees of albuminuria.

Design and methods

In a group of 842 diabetic patients GFR was estimated from standardized creatinine, with MDRD-Study and CKD-EPI equations, and their performance evaluated regarding clinical stages of albuminuria and chronic kidney disease (CKD).

Results

Patients with normoalbuminuria had higher eGFR when calculated by CKD-EPI, than MDRD-Study equation [median (IQR): 103 (91–115) vs 97 (85–113) mL/min/1.73 m2, P = 0.006, n = 364], which significantly influenced the prevalence of stage 1 CKD [eGFR > 90 mL/min/1.73 m2: 76.7% (CKD-EPI) vs. 65.1% (MDRD-Study), P = 0.005]. There were no differences between the eGFR values derived by two equations in patients with micro- and macroalbuminuria, and more advanced staging of CKD.

Conclusion

CKD-EPI equation might be a superior surrogate marker of GFR in patients with normoalbuminuria and hyperfiltration and could be used as a screening tool for early renal impairment in diabetes. It's validity as a marker of progression of diabetic nephropathy merits further investigation.

Highlights

► Two GFR equations were compared in diabetics with various stages of albuminuria. ► Normoalbuminuric patients had higher eGFR calculated with CKD-EPI equation. ► CKD-EPI-based eGFR might be better marker of early renal impairment in diabetes.

Introduction

Early changes in diabetic nephropathy involve increased urinary albumin excretion rate (AER) and/or a temporal increase in GFR (hyperfiltration), which are not necessarily inter-related [1]. Both albuminuric and non-albuminuric pathways to renal impairment have been identified in diabetes, emphasizing the importance of monitoring appropriate markers when screening for diabetic nephropathy. Current standards of clinical practice include annual measurement of AER and serum creatinine-estimated GFR for staging of CKD [2].

Serum creatinine-based formulas for GFR estimation have been routinely used to assess kidney function due to practical reasons, despite serious drawbacks regarding both biological and analytical precision and accuracy [3]. Global standardization of serum creatinine measurement and recalibration of routine methods to an isotope dilution mass spectrometry (IDMS) reference procedure resulted into reduction of between-method variability, which enabled improvements in creatinine-based eGFR equations and automated eGFR reporting [4].

The validity of the most widely used MDRD-Study equation [5] has been challenged in several studies conducted in diabetic patients [6], [7]. The most pronounced limitation of the MDRD-Study equation is a systematic underestimation of eGFR at higher levels (> 60 mL/min/1.73 m2), which might particularly compromise its suitability in patients with incipient kidney disease and hyperfiltration. In 2009, a new CKD-EPI equation for eGFR, based on a standardized creatinine was developed aiming to overcome limitations of MDRD-Study equation [8]. CKD-EPI equation was found to be more accurate than MDRD-Study equation, but its performance in diabetic patients has not been extensively evaluated. Recent reports have not confirmed better performance of CKD-EPI- over MDRD-Study equation in estimating GFR in diabetic patients [9]. Furthermore, a substantial difference in staging of CKD, depending on the equation use was found, implicating significant epidemiological and clinical impact in general population [10].

The aim of this study was to compare the performance of CKD-EPI and MDRD-Study equation in estimating GFR and CKD staging in a large cohort of diabetic patients with various degrees of albuminuria.

Section snippets

Design and methods

This observational study included retrospectively collected data from electronic medical records of diabetic patients (all Caucasians) visiting Day Hospital and Nephrology Department of the Vuk Vrhovac University Clinic form March to July 2011 for their annual check-up. Diagnosis of diabetes mellitus regardless of the type, gender and treatment, and predefined set of laboratory data (serum creatinine and urinary albumin excretion rate) were used as inclusion criteria, whereas data from the

Results

A total of 842 adult diabetic patients (48.2% males, 82% type 2 diabetes) were included in this study. Females were younger (median age: 55 vs 58, P = 0.013), had lower serum creatinine (65 ± 14 vs 80 ± 18 μmol/L, P < 0.001), but no gender-associated differences in eGFR, calculated by either equation, HbA1c and albuminuria were found (not shown).

Normoalbuminuric patients were younger and had lower HbA1c than micro- and macroalbuminuric patients (P < 0.05) whereas serum creatinine increased, and eGFR

Discussion

Our study showed significant difference in GFR estimated by two serum creatinine-based equations (CKD-EPI and MDRD-Study) in a large cohort of diabetic patients, which was particularly prominent in patients with normoalbuminuria. Serum creatinine and age, but not albuminuria, were identified as significant determinants of between-equation eGFR difference.

In the original study population CKD-EPI-equation based eGFR showed improved accuracy in subjects with GFR > 60 mL/min [8], but the evidence

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