Table 3.

Bias, precision, and accuracy of the MDRD and CG formulasa

NBland and Altman (ml/min per 1.73 m2)Accuracy within (% of Subjects)CRMSE (ml/min per 1.73 m2)
BiasPrecision15%30%50%
MDRD formula
    high GFRb1044−3.317.261.392.498.817.5
    low GFRc10511.38.554.882.993.38.6
    overall2095−1.013.758.087.296.013.8
CG formula
    high GFRb10440.419.456.188.097.419.4
    low GFRc10513.59.741.269.085.210.3
    overall20951.915.448.778.591.315.5
  • a Results obtained with these formulas were compared with GFR values obtained by measuring the renal clearance of 51Cr EDTA. Bias is defined as the mean difference between estimated and measured GFR. Precision is 1 SD of bias. Accuracy was assessed by determining the percentage of subjects who did not deviate >15, 30, and 50% from measured GFR and by calculating the combined root mean square error (CRMSE).

  • b Measured GFR ≥60 ml/min per 1.73 m2.

  • c Measured GFR <60 ml/min per 1.73 m2.