Using standardized serum creatinine values in the modification of diet in renal disease study equation for estimating glomerular filtration rate.
BACKGROUND
Glomerular filtration rate (GFR) estimates facilitate detection of chronic kidney disease but require calibration of the serum creatinine assay to the laboratory that developed the equation. The 4-variable equation from the Modification of Diet in Renal Disease (MDRD) Study has been reexpressed for use with a standardized assay.


OBJECTIVE
To describe the performance of the revised 4-variable MDRD Study equation and compare it with the performance of the 6-variable MDRD Study and Cockcroft-Gault equations.


METHODS
Comparison of estimated and measured GFR.


METHODS
15 clinical centers participating in a randomized, controlled trial.


METHODS
1628 patients with chronic kidney disease participating in the MDRD Study.


METHODS
Serum creatinine levels were calibrated to an assay traceable to isotope-dilution mass spectrometry. Glomerular filtration rate was measured as urinary clearance of 125I-iothalamate.


RESULTS
Mean measured GFR was 39.8 mL/min per 1.73 m2 (SD, 21.2). Accuracy and precision of the revised 4-variable equation were similar to those of the original 6-variable equation and better than in the Cockcroft-Gault equation, even when the latter was corrected for bias, with 90%, 91%, 60%, and 83% of estimates within 30% of measured GFR, respectively. Differences between measured and estimated GFR were greater for all equations when the estimated GFR was 60 mL/min per 1.73 m2 or greater.


CONCLUSIONS
The MDRD Study included few patients with a GFR greater than 90 mL/min per 1.73 m2. Equations were not compared in a separate study sample.


CONCLUSIONS
The 4-variable MDRD Study equation provides reasonably accurate GFR estimates in patients with chronic kidney disease and a measured GFR of less than 90 mL/min per 1.73 m2. By using the reexpressed MDRD Study equation with the standardized serum creatinine assay, clinical laboratories can report more accurate GFR estimates.
Levey
Andrew S
AS
Tufts-New England Medical Center, Boston, Massachusetts 02111, USA.
Coresh
Josef
J
Greene
Tom
T
Stevens
Lesley A
LA
Zhang
Yaping Lucy
YL
Hendriksen
Stephen
S
Kusek
John W
JW
Van Lente
Frederick
F
D000328:Adult; D015415:Biomarkers / Q000097:blood; D003404:Creatinine / Q000097:blood*; D005260:Female; D005919:Glomerular Filtration Rate; D006801:Humans; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D016032:Randomized Controlled Trials as Topic; D051436:Renal Insufficiency, Chronic / Q000097:blood* / Q000178:diet therapy / Q000503:physiopathology
D015415:Biomarkers; D003404:Creatinine