Measured versus Estimated Creatinine Clearance in the Elderly as an Index of Renal Function

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Abstract
Measured endogenous creatinine clearance (requiring 24 h urine collection) was compared to estimated (calculated) creatinine clearance obtained by 2 formulas and a nomogram (without urine collection) in 26 elderly nursing home residents. All were clinically stable and had adequate intakes of food and fluid. Of the 26 subjects, 23 had a normal value for serum creatinine concentration (0.7-1.5 mg/dl) with a mean of 1.1 mg/dl. Measured creatinine clearance (Ccr) was reduced in all patients despite a normal serum creatinine level. The mean Ccr was 47.2 ml/min, with values as low as 21.6 ml/min. Measured Ccr findings compared well with estimated (calculated) findings, the correlation coefficients being highly significant in all instances. If it is difficult or impossible to collect a 24 h urine specimen, a fairly accurate assessment of renal function may be obtained by using a simple formula (or nomogram) for estimating creatinine clearance on the basis of the patient''s age, weight (height) and serum creatinine level.