Estimating glomerular filtration rate: Cockcroft-Gault and Modification of Diet in Renal Disease formulas compared to renal inulin clearance.
OBJECTIVE
Evaluation of renal function by estimation of the glomerular filtration rate (GFR) is very important for the diagnosis and treatment of patients with chronic kidney disease (CKD). The Cockcroft-Gault (CG) and Modification of Diet in Renal Disease (MDRD) formulas are the most commonly used estimations.


METHODS
Estimated GFR values by each formula were compared with measured GFR (mGFR) by renal inulin clearance in 2208 European adults (46% women, 1.4% Caribbean blacks), with and without CKD, and mean mGFR 72.4 +/- 39.0 (range 2.2 to 177.2) ml/min/1.73 m(2).


RESULTS
Overall, the CG and MDRD formulas showed bias (mean difference) -3.5 ml/min/1.73 m(2) (5.3%), P < 0.001, and -9.8 ml/min/1.73 m(2) (-6.4%), P < 0.001; precision (SD of bias) 21.5 ml/min/1.73 m(2) (43.1%) and 20.0 ml/min/1.73 m(2) (33.0%); limits of agreement (2 SD by Bland-Altman method) 39.5 to -46.5 (range 86.0) ml/min/1.73 m(2) and 30.2 to -49.8 (range 80.0) ml/min/1.73 m(2); and accuracy within +/-30% of mGFR 70.8 and 69.0%, respectively. Both formulas showed a trend for decreasing accuracy with lower mGFR levels. According to the Kidney Disease Outcomes Quality Initiative (K/DOQI)-CKD classification's five GFR groups, the CG and MDRD formulas properly assigned 61.6 and 57.1% of the entire population and had a range of positive predictive values 42.6 to 81.8% and 39.6 to 85.2% and of negative predictive values 81.7 to 96.6% and 76.4 to 97.5%, respectively.


CONCLUSIONS
The CG and MDRD formulas had some limitations for proper GFR estimation and K/DOQI-CKD classification by GFR levels alone.
Botev
Rossini
R
Hawaii Permanente Medical Group, 3288 Moanalua Road, Honolulu, Hawaii 96819, USA. rossini.c.botev@kp.org
Mallié
Jean-Pierre
JP
Couchoud
Cecilé
C
Schück
Otto
O
Fauvel
Jean-Pierre
JP
Wetzels
Jack F M
JF
Lee
Nelson
N
De Santo
Natale G
NG
Cirillo
Massimo
M
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015331:Cohort Studies; D003404:Creatinine / Q000097:blood; D004032:Diet; D005260:Female; D005919:Glomerular Filtration Rate; D006801:Humans; D007444:Inulin; D007677:Kidney Function Tests / Q000379:methods* / Q000592:standards*; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D012042:Registries; D051436:Renal Insufficiency, Chronic / Q000175:diagnosis* / Q000178:diet therapy / Q000503:physiopathology; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D055815:Young Adult
D007444:Inulin; D003404:Creatinine