What is the Difference Between GFR and eGFR?
🆚 Go to Comparative Table 🆚The main difference between GFR and eGFR lies in the methods used to determine them:
- GFR (Glomerular Filtration Rate): This is a direct measurement of how well the kidneys are filtering blood by removing waste and extra water to make urine. GFR is considered the gold standard for assessing kidney function, but it is a complicated and time-consuming test that requires multiple blood draws over several hours.
- eGFR (estimated Glomerular Filtration Rate): This is a mathematically derived estimate of GFR, calculated using a patient's serum creatinine level, age, sex, and race. eGFR is less expensive, less time-consuming, and more widely available than direct GFR measurement. It is often calculated and reported by the laboratory measuring the creatinine level or can be calculated using an online eGFR calculator.
Several different mathematical formulas, such as CKD MDRD (Modification of Diet in Renal Disease) and CKD EPI (Chronic Kidney Disease Epidemiology), have been developed to calculate eGFR. These formulas compare the amount of creatinine in a person's blood against similar creatinine results for a reference population whose GFR has been measured directly. The formula then uses a conversion factor to determine the rate, which is then used to estimate the GFR.
While eGFR is not as accurate as direct GFR measurement, it is a practical and convenient alternative that provides valuable information about kidney function for diagnosing and managing kidney disease.
Comparative Table: GFR vs eGFR
Glomerular Filtration Rate (GFR) and Estimated Glomerular Filtration Rate (eGFR) are both used to measure kidney function, but they differ in their calculation methods and accuracy. Here is a table highlighting the differences between GFR and eGFR:
| Feature | GFR (Glomerular Filtration Rate) | eGFR (Estimated Glomerular Filtration Rate) |
|---|---|---|
| Definition | GFR is the actual measurement of how well the kidneys are filtering blood, removing waste, and producing urine. | eGFR is a calculated estimate of how well the kidneys are filtering blood, using factors such as serum creatinine, age, race, and gender. |
| Measurement Technique | GFR is measured using plasma or urinary clearance of an exogenous filtration marker, which is a complex procedure and not routinely performed. | eGFR is estimated using mathematical equations, such as the CKD-EPI creatinine equation, which requires only serum creatinine levels, age, and demographic factors like race and gender. |
| Accuracy | GFR is considered the gold standard for measuring kidney function, but it is not practical for routine clinical use. | eGFR is a simpler and more cost-effective method for estimating kidney function, but it may not be as accurate as GFR. Differences between eGFR and GFR can be higher at higher GFR levels and lower at lower GFR levels. |
| Uses | GFR is used to determine kidney function and diagnose chronic kidney disease (CKD). | eGFR is used to estimate kidney function, diagnose CKD, and help healthcare professionals develop clinical action plans based on a patient's CKD classification. |
In summary, GFR is the actual measurement of kidney function, while eGFR is an estimated value calculated using mathematical equations. Although GFR is the gold standard for measuring kidney function, eGFR is more practical and cost-effective for routine clinical use, making it a valuable tool for diagnosing and managing kidney diseases.
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