Original Investigation
Pathogenesis and Treatment of Kidney Disease
Comparative Performance of the CKD Epidemiology Collaboration (CKD-EPI) and the Modification of Diet in Renal Disease (MDRD) Study Equations for Estimating GFR Levels Above 60 mL/min/1.73 m2

https://doi.org/10.1053/j.ajkd.2010.03.026Get rights and content

Background

The Modification of Diet in Renal Disease (MDRD) Study equation underestimates measured glomerular filtration rate (GFR) at levels >60 mL/min/1.73 m2, with variable accuracy among subgroups; consequently, estimated GFR (eGFR) ≥60 mL/min/1.73 m2 is not reported by clinical laboratories. Here, performance of a more accurate GFR-estimating equation, the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation, is reported by level of GFR and clinical characteristics.

Study Design

Test of diagnostic accuracy.

Setting & Participants

Pooled data set of 3,896 people from 16 studies with measured GFR (not used for the development of either equation). Subgroups were defined by eGFR, age, sex, race, diabetes, prior solid-organ transplant, and body mass index.

Index Tests

eGFR from the CKD-EPI and MDRD Study equations and standardized serum creatinine.

Reference Test

Measured GFR using urinary or plasma clearance of exogenous filtration markers.

Results

Mean measured GFR was 68 ± 36 (SD) mL/min/1.73 m2. For eGFR <30 mL/min/1.73 m2, both equations have similar bias (median difference compared with measured GFR). For eGFR of 30-59 mL/min/1.73 m2, bias was decreased from 4.9 to 2.1 mL/min/1.73 m2 (57% improvement). For eGFR of 60-89 mL/min/1.73 m2, bias was decreased from 11.9 to 4.2 mL/min/1.73 m2 (61% improvement). For eGFR of 90-119 mL/min/1.73 m2, bias was decreased from 10.0 to 1.9 mL/min/1.73 m2 (75% improvement). Similar or improved performance was noted for most subgroups with eGFR <90 mL/min/1.73 m2, other than body mass index <20 kg/m2, with greater variation noted for some subgroups with eGFR ≥90 mL/min/1.73 m2.

Limitations

Limited number of elderly people and racial and ethnic minorities with measured GFR.

Conclusions

The CKD-EPI equation is more accurate than the MDRD Study equation overall and across most subgroups. In contrast to the MDRD Study equation, eGFR ≥60 mL/min/1.73 m2 can be reported using the CKD-EPI equation.

Section snippets

Sources of Data and Measurements

The CKD-EPI is a research group funded by the National Institute of Diabetes, Digestive and Kidney Diseases to address challenges in the study and care of CKD, including the development and validation of improved GFR-estimating equations by pooling data from research studies and clinical populations (hereafter referred to as “studies”).7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26

The methods for selection and pooling of studies have been described previously5 and

Results

Table 1 lists clinical characteristics of participants in the external validation data set (not used for the development of either equation) according to eGFR computed using the CKD-EPI equation.30 Briefly, approximately 49% of people had eGFR <60 mL/min/1.73 m2, 25% had eGFR of 60-89 mL/min/1.73 m2, and 26% had eGFR >90 mL/min/1.73 m2. Approximately 15% of participants were older than 65 years. Median age of participants older than 65 years was 71 years (25th-75th percentile and 99th

Discussion

There are numerous studies attempting to identify a replacement for serum creatinine as a filtration marker, but no single marker has thus been definitely established.18, 31, 32, 33, 34 Therefore, despite acknowledged weaknesses,35, 36 GFR estimates based on serum creatinine will remain the mainstay of clinical assessment of kidney function for the foreseeable future, and use of equations that improve the accuracy of GFR estimated from serum creatinine is an important goal. A new

Acknowledgements

Aghogho Okparavero, MBBS, MPH provided assistance in communications and manuscript preparation.

Portions of this report were presented at the American Society of Nephrology Annual Conference held November 6-9, 2008, in Philadelphia, PA.

The membership of the CKD-EPI, including investigators, research staff, collaborators, and the Scientific Advisory Committee, has been published previously.5

Support: This study was supported by grants UO1 DK 053869, UO1 DK 067651, UO1 DK 35073, and K23-DK081017.

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    Originally published online as doi:10.1053/j.ajkd.2010.03.026 on June 17, 2010.

    Because an author of this manuscript is an editor for AJKD, the peer-review and decision-making processes were handled entirely by an Associate Editor (Kamyar Kalantar-Zadeh, MD, MPH, PhD, Harbor-UCLA Medical Center) who served as Acting Editor-in-Chief. Details of the journal's procedures for potential editor conflicts are given in the Editorial Policies section of the AJKD website.

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