title: Using standardized serum creatinine values in the modification of diet in renal disease study equation for estimating glomerular filtration rate.
abstract: 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.
authors.affiliation: Tufts-New England Medical Center, Boston, Massachusetts 02111, USA.
authors.forename: Andrew S
authors.initials: AS
authors.lastname: Levey
authors.forename: Josef
authors.initials: J
authors.lastname: Coresh
authors.forename: Tom
authors.initials: T
authors.lastname: Greene
authors.forename: Lesley A
authors.initials: LA
authors.lastname: Stevens
authors.forename: Yaping Lucy
authors.initials: YL
authors.lastname: Zhang
authors.forename: Stephen
authors.initials: S
authors.lastname: Hendriksen
authors.forename: John W
authors.initials: JW
authors.lastname: Kusek
authors.forename: Frederick
authors.initials: F
authors.lastname: Van Lente
mesh_terms: 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
chemical_list: D015415:Biomarkers; D003404:Creatinine