Estimating glomerular filtration rates by use of both cystatin C and standardized serum creatinine avoids ethnicity coefficients in Asian patients with chronic kidney disease.
BACKGROUND
The Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation is most accurate for estimating glomerular filtration rate (GFR) but requires an adjustment for African-American patients. Estimation equations are also improved with the use of serum cystatin C combined with standardized creatinine. Combination equations have been derived by the CKD-EPI and Chinese investigators. We investigated whether these cystatin C-based equations improve estimation adequately, so that adjustments for ethnicity are not required in a multiethnic Asian population with chronic kidney disease (CKD).


METHODS
This was a cross-sectional study of 232 stable CKD patients who underwent GFR measurements using 3-sample plasma clearances of (99m)Tc-DTPA, and for whom serum cystatin C and creatinine were quantified.


RESULTS
For all patients, the median biases with cystatin C equations were generally greater than with the CKD-EPI equation, and precision and root mean square error (RMSE) were not significantly better. However, the combination serum creatinine and cystatin C equation improved the precision, RMSE, and percentage of estimated GFR to within 15% and 30% of the measured GFR (57.3% vs 50.0%, 88.4% vs 82.8%, respectively). The derived ethnicity coefficients for the combination equation were all >1 (1.009-1.082) but small, suggesting that coefficients are not required. The Chinese-specific equations were more biased and performed more poorly than the CKD-EPI equation.


CONCLUSIONS
The use of a cystatin C and creatinine combination equation for estimating GFR in a multiethnic Asian population with CKD does not require ethnicity coefficients because the derived coefficients are very close to each other.
Division of Nephrology, Department of Medicine, Yong Loo Lin School of Medicine, National University of Singapore, Singapore. mdctbw@nus.edu.sg
Boon Wee
BW
Teo
Hui
H
Xu
Danhua
D
Wang
Jialiang
J
Li
Arvind Kumar
AK
Sinha
Borys
B
Shuter
Sunil
S
Sethi
Evan J C
EJ
Lee
D000368:Aged; D044466:Asian People; D002908:Chronic Disease; D003404:Creatinine / Q000097:blood*; D003430:Cross-Sectional Studies; D055316:Cystatin C / Q000097:blood*; D005260:Female; D005919:Glomerular Filtration Rate; D006801:Humans; D007674:Kidney Diseases / Q000208:ethnology / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D012015:Reference Standards; D044465:White People
D055316:Cystatin C; D003404:Creatinine