A new equation to estimate glomerular filtration rate.
BACKGROUND
Equations to estimate glomerular filtration rate (GFR) are routinely used to assess kidney function. Current equations have limited precision and systematically underestimate measured GFR at higher values.


OBJECTIVE
To develop a new estimating equation for GFR: the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation.


METHODS
Cross-sectional analysis with separate pooled data sets for equation development and validation and a representative sample of the U.S. population for prevalence estimates.


METHODS
Research studies and clinical populations ("studies") with measured GFR and NHANES (National Health and Nutrition Examination Survey), 1999 to 2006.


METHODS
8254 participants in 10 studies (equation development data set) and 3896 participants in 16 studies (validation data set). Prevalence estimates were based on 16,032 participants in NHANES.


METHODS
GFR, measured as the clearance of exogenous filtration markers (iothalamate in the development data set; iothalamate and other markers in the validation data set), and linear regression to estimate the logarithm of measured GFR from standardized creatinine levels, sex, race, and age.


RESULTS
In the validation data set, the CKD-EPI equation performed better than the Modification of Diet in Renal Disease Study equation, especially at higher GFR (P < 0.001 for all subsequent comparisons), with less bias (median difference between measured and estimated GFR, 2.5 vs. 5.5 mL/min per 1.73 m(2)), improved precision (interquartile range [IQR] of the differences, 16.6 vs. 18.3 mL/min per 1.73 m(2)), and greater accuracy (percentage of estimated GFR within 30% of measured GFR, 84.1% vs. 80.6%). In NHANES, the median estimated GFR was 94.5 mL/min per 1.73 m(2) (IQR, 79.7 to 108.1) vs. 85.0 (IQR, 72.9 to 98.5) mL/min per 1.73 m(2), and the prevalence of chronic kidney disease was 11.5% (95% CI, 10.6% to 12.4%) versus 13.1% (CI, 12.1% to 14.0%).


CONCLUSIONS
The sample contained a limited number of elderly people and racial and ethnic minorities with measured GFR.


CONCLUSIONS
The CKD-EPI creatinine equation is more accurate than the Modification of Diet in Renal Disease Study equation and could replace it for routine clinical use.


BACKGROUND
National Institute of Diabetes and Digestive and Kidney Diseases.
Levey
Andrew S
AS
Tufts Medical Center, Boston, Massachusetts 02111, USA.
Stevens
Lesley A
LA
Schmid
Christopher H
CH
Zhang
Yaping Lucy
YL
Castro
Alejandro F
AF
Feldman
Harold I
HI
Kusek
John W
JW
Eggers
Paul
P
Van Lente
Frederick
F
Greene
Tom
T
Coresh
Josef
J
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002908:Chronic Disease; D003404:Creatinine / Q000097:blood; D003430:Cross-Sectional Studies; D005260:Female; D005919:Glomerular Filtration Rate; D006801:Humans; D007674:Kidney Diseases / Q000175:diagnosis / Q000453:epidemiology*; D008297:Male; D008875:Middle Aged; D009749:Nutrition Surveys; D015995:Prevalence; D015203:Reproducibility of Results; D014481:United States / Q000453:epidemiology
D003404:Creatinine