Revised Equations for Estimated GFR From Serum Creatinine in Japan
Received 28 February 2008; accepted 16 December 2008. published online 02 April 2009.
Refers to article:
GFR Estimation in Japan and China: What Accounts for the Difference?
Andrew D. Rule, Boon Wee Teo
American Journal of Kidney Diseases
June 2009 (Vol. 53, Issue 6, Pages 932-935) Full Text |
Full-Text PDF (153 KB)
Background
Estimation of glomerular filtration rate (GFR) is limited by differences in creatinine generation among ethnicities. Our previously reported GFR-estimating equations for Japanese had limitations because all participants had a GFR less than 90 mL/min/1.73 m2 and serum creatinine was assayed in different laboratories.
Study Design
Diagnostic test study using a prospective cross-sectional design. New equations were developed in 413 participants and validated in 350 participants. All samples were assayed in a central laboratory.
Setting & Participants
Hospitalized Japanese patients in 80 medical centers. Patients had not participated in the previous study.
Reference Test
Measured GFR (mGFR) computed from inulin clearance.
Index Test
Estimated GFR (eGFR) by using the modified isotope dilution mass spectrometry (IDMS)-traceable 4-variable Modification of Diet in Renal Disease (MDRD) Study equation using the previous Japanese Society of Nephrology Chronic Kidney Disease Initiative (JSN-CKDI) coefficient of 0.741 (equation 1), the previous JSN-CKDI equation (equation 2), and new equations derived in the development data set: modified MDRD Study using a new Japanese coefficient (equation 3), and a 3-variable Japanese equation (equation 4).
Measurements
Performance of equations was assessed by means of bias (eGFR − mGFR), accuracy (percentage of estimates within 15% or 30% of mGFR), root mean squared error, and correlation coefficient.
Results
In the development data set, the new Japanese coefficient was 0.808 (95% confidence interval, 0.728 to 0.829) for the IDMS–MDRD Study equation (equation 3), and the 3-variable Japanese equation (equation 4) was eGFR (mL/min/1.73 m2) = 194 × Serum creatinine−1.094 × Age−0.287 × 0.739 (if female). In the validation data set, bias was −1.3 ± 19.4 versus −5.9 ± 19.0 mL/min/1.73 m2 (P = 0.002), and accuracy within 30% of mGFR was 73% versus 72% (P = 0.6) for equation 3 versus equation 1 and −2.1 ± 19.0 versus −7.9 ± 18.7 mL/min/1.73 m2 (P < 0.001) and 75% versus 73% (P = 0.06) for equation 4 versus equation 2 (P = 0.06), respectively.
Limitation
Most study participants had chronic kidney disease, and some may have had changing GFRs.
Conclusion
The new Japanese coefficient for the modified IDMS–MDRD Study equation and the new Japanese equation are more accurate for the Japanese population than the previously reported equations.
ABSTRACT