Estimating Glomerular Filtration Rates by Use of Both Cystatin C and Standardized Serum Creatinine Avoids Ethnicity Coefficients in Asian Patients with Chronic Kidney Disease

• Published in: Clinical chemistry (Baltimore, Md.) Md.), 2012-02, Vol.58 (2), p.450-457
• Main Authors: BOON WEE TEO, HUI XU, DANHUA WANG, JIALIANG LI, ARVIND KUMAR SINHA, SHUTER, Borys, SETHI, Sunil, LEE, Evan J. C
• Format: Article
• Language: English
• Subjects: Accuracy; Aged; Analytical, structural and metabolic biochemistry; Asian Continental Ancestry Group; Awards & honors; Bias; Biological and medical sciences; Chronic Disease; Creatinine - blood; Cross-Sectional Studies; Cystatin C - blood; Disease; Epidemiology; Ethnicity; European Continental Ancestry Group; Female; Fundamental and applied biological sciences. Psychology; Glomerular Filtration Rate; Humans; Investigative techniques, diagnostic techniques (general aspects); Kidney diseases; Kidney Diseases - ethnology; Kidney Diseases - physiopathology; Kidneys; Male; Mean square errors; Measurement techniques; Medical sciences; Middle Aged; Molecular biophysics; Reference Standards
• ISSN: 0009-9147; 1530-8561
• DOI: 10.1373/clinchem.2011.172346

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). 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. 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. 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.