Is the new Mayo Clinic Quadratic equation useful for the estimation of glomerular filtration rate in type 2 diabetic patients?
OBJECTIVE
To test the Mayo Clinic Quadratic (MCQ) equation against isotopic glomerular filtration rate, compared with the Modification of Diet in Renal Disease (MDRD) and the Cockcroft-Gault formulas, in type 2 diabetes.


METHODS
Based on values obtained with iothalamate, 118 type 2 diabetic patients were divided into three groups according to renal function: hyperfiltration (26), normal function (56), or chronic kidney disease (CKD) stages 3-4 (36). ANOVA, the Bland-Altman procedure, and Lins coefficient (Rc) were performed to study accuracy.


RESULTS
In the hyperfiltration and normal function groups, all prediction equations significantly underestimated the value obtained with isotopic glomerular filtration rate (P < 0.05). In the CKD group, all equations also presented significant differences with the isotopic method. However, MDRD had a bias of -5.3 (Rc 0.452), Cockcroft-Gault formula -0.2 (Rc 0.471), and the MCQ -4.5 (Rc 0.526).


CONCLUSIONS
The MCQ and prediction equations proved inaccurate (excessive underestimation) in type 2 diabetic patients with hyperfiltration or normal renal function. With regard to CKD, the results obtained provided no evidence of superiority of the MCQ over the MDRD or the Cockcroft-Gault formula.
Department of Nephrology, Hospital de Terrassa, Barcelona, Spain. 34989nfb@comb.es
Néstor
N
Fontseré
Jordi
J
Bonal
Isabel
I
Salinas
Manel Ramírez
MR
de Arellano
Jose
J
Rios
Ferran
F
Torres
Anna
A
Sanmartí
Ramón
R
Romero
D000368:Aged; D000704:Analysis of Variance; D003287:Contrast Media; D003924:Diabetes Mellitus, Type 2 / Q000503:physiopathology*; D005260:Female; D005919:Glomerular Filtration Rate; D006801:Humans; D007483:Iothalamic Acid; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results
D003287:Contrast Media; D007483:Iothalamic Acid