Sobh formula: a new formula for estimation of creatinine clearance in healthy subjects and patients with chronic renal disease

Abstract

Background: Cockcroft-Gault formula overestimates creatinine clearance (Ccr) in obese or edematous patients. This limitation urged us to develop a new formula that can overcome the limitation of Cockcroft-Gault formula.

Methods: We developed a new formula suitable for rapid bedside estimation of creatinine clearance in healthy adults and elderly persons and patients with chronic renal disease considering the surface area as a reliable factor for estimation of creatinine clearance. This cross sectional study included 182 individuals (healthy persons and patients with chronic kidney disease). Ccr was estimated by different methods including 24 hours urine collection, Cockcroft-Gault equation, and our new formula, and 99mTc-DTPA isotope clearance which was considered as a standard method for comparison between the other methods.

Results: Our new formula had a statistically significant higher correlation coefficient with the standard 99mTc-DTPA isotope clearance for all groups included in this study (r=0.97) than either Cockcroft-Gault formula (r=0.90) or 24 hours urine collection method (r=0.88).

Conclusion: Our formula is a step forward for a better bedside assessment of kidney function in both healthy individuals and patients with chronic kidney disease.