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Creatinine Clearance and Estimated Glomerular Filtration Rate--When are they Interchangeable
Insights
This study compared glomerular filtration rate equations for predicting creatinine clearance in 500 patients. The Modification of Diet in Renal Disease (MDRD) and CKD-EPI equations showed high accuracy, especially in advanced kidney disease stages.
Area of Science:
- Nephrology
- Clinical Chemistry
- Biostatistics
Background:
- Accurate estimation of glomerular filtration rate (GFR) is crucial for managing chronic kidney disease (CKD).
- Several equations exist to estimate GFR, but their suitability for predicting creatinine clearance (CrCl) across different patient demographics and CKD stages requires evaluation.
- The Cockcroft-Gault (C-G), Modification of Diet in Renal Disease (MDRD), and CKD-EPI equations are commonly used but may have varying performance.
Purpose of the Study:
- To determine the most suitable glomerular rate equation for predicting creatinine clearance (CrCl).
- To assess the impact of CKD stage, body-mass index (BMI), diabetes, and age on the predictive accuracy of these equations.
- To propose potential adjustments for equations in specific patient populations, such as overweight individuals.
Main Methods:
- Retrospective analysis of data from 500 hospital patients.
- Calculation of GFR using the Cockcroft-Gault (C-G), MDRD, and CKD-EPI equations.
- Comparison of equation-derived GFR with measured CrCl, including analysis of diagnostic accuracy using ROC plots and Passing-Bablok regression, stratified by patient characteristics and CKD stage.
Main Results:
- All equations demonstrated high correlations with CrCl across various patient groups (diabetes, overweight, elderly).
- No significant difference in diagnostic accuracy between MDRD and CKD-EPI was observed at common CrCl cutoffs (60 and 90 ml/min/1.73 m2).
- Overweight patients showed a higher prevalence of normal CrCl with decreased GFR using MDRD and CKD-EPI, suggesting potential overestimation by CrCl in this group. Agreement between CrCl and MDRD/CKD-EPI was limited to advanced CKD stages (G4 and G5).
Conclusions:
- The MDRD and CKD-EPI equations are highly correlated with CrCl and suitable for predicting renal function across diverse patient populations.
- CrCl may overestimate GFR in overweight individuals, indicating a need for potential correction.
- Simultaneous use of CrCl with MDRD or CKD-EPI is validated only in patients with severely decreased GFR (stages G4 and G5).
Abstract:
Study goal was to examine which of glomerular rate equations is most suitable for prediction of creatinine clearance (CrCl). Using a retrospective review of data from 500 hospital patients we calculated glomerular filtration rate according to Cockcroft-Gault equation (C-G), Modification of Diet in Renal Disease Study equation (MDRD) and Chronic Kidney Disease Epidemiology Collaboration equation (CKD-EPI). We determined if results of these equations were compatible with CrCl, and does stage of kidney disease, body-mass index (BMI), diabetes or old age have an impact on their ability to predict creatinine clearance. All of the equations showed high correlations with CrCl, regardless of diabetes, overweight or old age. There was no significant difference (p<0.05) between diagnostic accuracy when comparing ROC plots for MDRD and CKD-EPIat CrCl cut offs of 60 ml/min/1.73 m2 and 90 ml/min/1.73 m2 when analyzing data for all patients, older patients (>65 years) and diabetics. The percentage of overweight patients (BMI > or = 25) in patients with normal CrCl and decreased GFR was 64.81% for C-G, 92.04% for MDRD and 91.36% for CKD-EPI. Large number of overweight patients with normal CrCl and decreased GFR would indicate that CrCl overestimates GFR in overweight patients. The simple correction in CrCl for obese subjects is purposed. Passing-Bablok regression showed agreement between CrCl and MDRD and CrCl and CKD-EPI only in cases of severely decreased GFR (G4 and G5 stage of chronic kidney disease). Only in these stages of chronic kidney disease can CrCl and MDRD or CrCl and CKD-EPI be used simultaneously.
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