A quick and simple estimate of creatinine clearance

Area of Science:

• Nephrology
• Clinical Chemistry
• Biostatistics

Background:

• Established methods for estimating glomerular filtration rate (GFR), such as the Cockcroft-Gault (C-G) and MDRD study equations, require complex calculations and multiple parameters.
• There is a need for a simpler, rapid method to estimate renal function at the bedside.

Purpose of the Study:

• To derive and validate a new, simplified equation for estimating creatinine clearance (eCCr).
• To compare the accuracy of the new eCCr formula against the MDRD and C-G equations.

Main Methods:

• A cohort of 61 patients was studied.
• A novel formula for eCCr was developed: eCCr (male) = weight/creatinine; eCCr (female) = weight x 0.84/creatinine (weight in kg).
• The eCCr was compared to the MDRD (long and short) and C-G equations using intraclass correlation (ICC) and kappa coefficients for patient staging.

Main Results:

• Intraclass correlation coefficients (ICCs) indicated good overall agreement between eCCr and other formulae (ICC=0.84).
• For estimating GFR <60, the MDRD short equation showed the best agreement (kappa=0.88), followed by eCCr (kappa=0.69, 'fair' agreement), and C-G (kappa=0.56).
• ROC curve analysis demonstrated strong performance for eCCr as an estimate of MDRD long (AUC=0.90) and C-G (AUC=0.94).

Conclusions:

• The eCCr formula provides a simple, rapid bedside estimation of GFR.
• eCCr demonstrates reasonable mathematical agreement with established MDRD and C-G equations.
• This simplified estimation can assist physicians in adjusting drug dosages or determining the need for formal GFR assessment.