Original Investigation
Pathogenesis and Treatment of Kidney Disease
Modification of the CKD Epidemiology Collaboration (CKD-EPI) Equation for Japanese: Accuracy and Use for Population Estimates

https://doi.org/10.1053/j.ajkd.2010.02.344Get rights and content

Introduction

We previously reported a modification to the Modification of Diet in Renal Disease (MDRD) Study equation for use in Japan. Recently, the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) developed a new equation that is more accurate and yields a lower CKD prevalence estimate in the United States than the MDRD Study equation. We modified the CKD-EPI equation for use in Japan, compared its accuracy with the Japanese modification of the MDRD Study equation, and compared the prevalence of CKD in Japan using both equations.

Design

A diagnostic test study comparing the Japanese coefficient–modified CKD-EPI equation and Japanese coefficient–modified MDRD Study equation and a cross-sectional study comparing distribution of estimated glomerular filtration rate and prevalence of CKD in participants in a Japanese annual health check program.

Setting & Participants

763 Japanese patients (413 for development and 350 for validation) were included. Prevalence estimates were based on 574,024 participants from the annual health check program.

Index Test

Japanese modification of the MDRD Study and CKD-EPI equations.

Reference Test

Inulin clearance.

Results

The Japanese coefficient of the modified CKD-EPI equation was 0.813 (95% CI, 0.794-0.833). In the validation data set, the modified CKD-EPI equation performed better than the modified MDRD Study equation. Bias (measured GFR [mGFR] − eGFR) was 0.4 ± 17.8 (SD) versus 1.3 ± 19.8 mL/min/1.73 m2 overall, respectively (P = 0.02); 7.3 ± 20.6 versus 7.8 ± 22.2 mL/min/1.73 m2 for participants with mGFR ≥60 mL/min/1.73 m2, respectively (P < 0.001); and −4.4 ± 13.8 versus −3.3 ± 15.6 mL/min/1.73 m2 for participants with mGFR <60 mL/min/1.73 m2, respectively (P = 0.5). The modified CKD-EPI equation yields a lower estimated prevalence of CKD than the modified MDRD Study equation (7.9% vs 10.0%), primarily because of a lower estimated prevalence of stage 3 (5.2% vs 7.5%).

Limitation

Most study participants had CKD. The study population contained a limited number of participants with mGFR ≥90 mL/min/1.73 m2.

Conclusion

The Japanese coefficient–modified CKD-EPI equation is more accurate than the Japanese coefficient–modified MDRD Study equation and leads to a lower estimated prevalence of CKD in Japan.

Section snippets

Participants

To perform a diagnostic test study to compare the modified CKD-EPI and modified MDRD Study equations, we used same data sets from which the Japanese coefficient of the MDRD Study equation was developed and validated. Details of participants were reported previously.3 Briefly, 763 Japanese patients in 80 medical centers were included. They were divided into a development data set (413 participants) and a validation data set (350 participants). GFR was measured using inulin renal clearance. Serum

Modifying the CKD-EPI Equation for a Japanese Population

The coefficient to modify the CKD-EPI equation for Japanese, calculated from the development data set of 413 participants (for whom clinical characteristics are listed in Table 1), was found to be 0.813 (95% confidence interval, 0.794-0.833).

Diagnostic Test Study

We used a diagnostic test design to compare the Japanese coefficient–modified CKD-EPI and MDRD Study equations, which are listed in Table 2.

Discussion

We previously reported a Japanese coefficient of 0.808 for the MDRD Study equation.3 In the present study, we obtained the Japanese coefficient of 0.813 (95% confidence interval, 0.794-0.833) for the CKD-EPI equation. The values are similar in both equations. The observation that correction coefficients are less than 1.0 indicates lower serum creatinine levels in Japanese than in whites with equivalent GFRs, probably because of the lower skeletal muscle mass found in Japanese compared with

Acknowledgements

Support: This study was supported by a grant from the Japanese Society of Nephrology.

Financial Disclosure: The authors declare that they have no relevant financial interests.

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Originally published online as doi:10.1053/j.ajkd.2010.02.344 on April 23, 2010.

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