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Geriatric renal function: estimating glomerular filtration in an ambulatory elderly population
D Baracskay1, D Jarjoura, A Cugino
1Cleveland Clinic Foundation, Ohio, USA.
Clinical Nephrology
|April 1, 1997
Summary
Estimating kidney function in older adults is challenging as serum creatinine can be misleading. This study found that common formulas like Cockroft-Gault and 100/SC are inaccurate for estimating glomerular filtration rate (GFR) in the elderly.
Area of Science:
- Geriatric Medicine
- Nephrology
- Pharmacology
Background:
- Serum creatinine levels may not accurately reflect declining glomerular filtration rate (GFR) in elderly individuals.
- Accurate GFR estimation is crucial for drug dosage adjustments and early diagnosis of renal disease in geriatrics.
- Existing simplified GFR estimators have limitations in accuracy compared to gold standards.
Purpose of the Study:
- To critically evaluate three common GFR estimators: creatinine clearance (CC), Cockroft-Gault (CG), and 100 over serum creatinine (100/SC).
- To compare these estimators against iothalamate clearance (IC) in healthy ambulatory geriatric subjects.
- To assess the accuracy and reliability of these GFR estimations in an aging population.
Main Methods:
- A study involving 41 healthy ambulatory geriatric subjects aged 65-85.
- Comparison of GFR estimates from CC, CG, and 100/SC against iothalamate clearance (IC) as the gold standard.
- Analysis of correlation, bias, and error (standard error) of each estimator relative to IC, considering age-related changes.
Main Results:
- Iothalamate clearance (IC) declined by 1 ml/min per year of age.
- Creatinine clearance (CC) showed a similar age-related decline and correlated well with IC (r=0.83), with moderate error (17%).
- 100/SC and CG formulas demonstrated significant inaccuracies, with 100/SC showing large bias and no age correction, while CG also proved unreliable (r=0.5, SE=23.8).
- A novel age-corrected formula showed improvement over CG but still had substantial error (SE=16.4).
Conclusions:
- Serum creatinine-based GFR estimations, including CC, CG, and 100/SC, may not be sufficiently accurate for clinical use in the elderly.
- Age is a critical factor in GFR estimation for geriatric populations.
- Further research is needed to develop reliable GFR estimation methods for older adults to ensure safe and effective medication management and disease detection.