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.
To develop a new estimating equation for GFR: the Chronic Kidney Disease Epidemiology
Collaboration (CKD-EPI) equation.
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.
Research studies and clinical populations ("studies") with measured GFR and NHANES
(National Health and Nutrition Examination Survey), 1999 to 2006.
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
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.
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%).
The sample contained a limited number of elderly people and racial and ethnic minorities
with measured GFR.
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.
National Institute of Diabetes and Digestive and Kidney Diseases.