Difficulties in estimating glomerular filtration rate in the elderly.

Area of Science:

• Nephrology
• Clinical Pharmacology
• Geriatrics

Background:

• Glomerular filtration rate (GFR) estimation is crucial for clinical decisions, often relying on creatinine clearance.
• Accurate GFR assessment can be hindered by difficulties in obtaining reliable urine samples.
• Existing predictive formulas for GFR may have limitations in accuracy.

Purpose of the Study:

• To evaluate the reliability of estimating creatinine clearance from serum creatinine levels using the Cockcroft-Gault equation.
• To assess the feasibility of obtaining satisfactory 24-hour urine collections in elderly outpatients.

Main Methods:

• Comparison of measured 24-hour creatinine clearance with values calculated by the Cockcroft-Gault equation in 50 inpatients.
• Assessment of 24-hour urine collection success rates in 19 healthy elderly outpatients.

Main Results:

• A moderate correlation was observed between measured and calculated creatinine clearance, potentially insufficient for clinical use.
• A significant number of elderly outpatients were unable to provide adequate 24-hour urine collections.

Conclusions:

• Current bedside methods for estimating GFR, including predictive formulas and urine collection, are unreliable, especially in the elderly and renally impaired.
• Direct measurement of drug levels is advised in elderly patients and those with renal insufficiency due to GFR estimation uncertainties.