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. Author manuscript; available in PMC: 2019 Mar 1.
Published in final edited form as: Dig Dis Sci. 2018 Feb 1;63(3):665–675. doi: 10.1007/s10620-017-4897-z

Table 5.

Bias, Precision and Accuracy of Measured and Estimated Cr Clearance in 91 Subjects with Cirrhosis

Measured Cr Clearance Estimated Cr Clearance1 P Value3
Bias2 1.13 −23.15 <0.0001
Precision2 34.43 26.72 0.066
Accuracy (1-P30)2 42.86 56.04 0.073
Accuracy (1-P20)2 57.14 71.43 0.060
Accuracy (RMSE)2 34.45 35.36 0.829
1

Estimated Cr clearance in ml/min/1.73m2= (Estimated Cr production rate in mg/kg/day using Mitch and Walser equation38)*(weight in kg*100 ml)*(1.73 m2)/(serum Cr in mg/dl)*(1440 min)*(body surface area in m2).

2

Bias=Mean of the difference scores (difference score=measured GFR-measured Cr clearance or estimated Cr clearance for each subject); a positive bias indicates that estimated Cr clearance on average underestimates measured GFR. Precision=Standard deviation of difference score. Accuracy (1-P30)=Percentage of measured or estimated Cr clearance values that differ by greater than 30%. Accuracy (1-P20)= Percentage of measured or estimated Cr clearance values that differ by greater than 20% of measured GFR. Accuracy (RMSE)=Root mean squared error (RMSE). Lower values for precision and accuracy (1- P30), (1-P20) and RMSE indicate higher precision and accuracy for measured and estimated Cr clearance.

3

P values compare the performance of estimated Cr clearance to measured Cr clearance. P values for bias indicate difference in the location of bias, not the difference in the magnitude.