What is the Difference Between GFR and eGFR

The main difference between GFR and eGFR is that GFR or glomerular filtration rate describes the flow rate of the filtered fluid through kidney whereas eGFR or the estimated glomerular filtration rate is a number that estimates GFR. Furthermore, GFR can be measured by plasma or urinary clearance of an ideal filtration marker such as insulin, while eGFR can be calculated from a single blood test result such as serum creatinine. 

GFR and eGFR are two types of measurements of renal function. Moreover, they are important for the characterization of chronic kidney disease. 

Key Areas Covered 

1. What is GFR
     – Definition, Measurement, Importance
2. What is eGFR
     – Definition, Measurement, Importance
3. What are the Similarities Between GFR and eGFR
     – Outline of Common Features
4. What is the Difference Between GFR and eGFR
     – Comparison of Key Differences

Key Terms 

Chronic Kidney Disease, eGFR, GFR, Renal Function, Serum Creatinine

What is GFR

GFR (glomerular filtration rate) is the total filtration rate of a functioning nephron in the kidney. It also reflects kidney function. Therefore, it is an important measurement for the diagnosis, prognosis, and treatment of kidney disease. However, GFR is an indirect measurement. Generally, it is measured in terms of the rate of filtration of an ideal filtration marker by the kidney. Furthemore, some of the Gold standard markers include insulin, iohexol or iothalamate. But, in clinical practice, creatinine is the endogenous marker used for the determination of GFR.

Figure 1: Function of the Nephron

Furthermore, the normal GFR value of most healthy people is 90 mL/min/1.73 m2 or higher. However, it can be lowered up to 60-89 mL/min without kidney damage. The normal GFR value ranges with age, gender, and body size. However, lower GFR values within more than three months, along with another symptom like persisting protein in the urine indicates early kidney disease. Also, a GFR, which is <60 mL/min for more than three months, indicates chronic kidney disease (CKD). 

What is eGFR 

eGFR (estimated glomerular filtration rate) is the calculated value of GFR by means of serum creatinine levels. The main importance of eGFR is that it can be measured by a single blood test result using a formula. On the other hand, the calculation of GFR requires to take cooperate measurements of substances in both blood and urine. However, the values of both GFR and eGFR are similar to each other. Moreover, for adults, the normal GFR value has to be more than 90 mL/min. 

Similarities Between GFR and eGFR 

• GFR and eGFR are two types of measurements of renal function. 
• They measure the excretory function of the kidney and important for diagnosing mainly chronic kidney disease. 
• Moreover, they help to diagnose other diseases, such as albuminuria and kidney diseases.  

Difference Between GFR and eGFR 

Definition

GFR refers to the rate of blood flow through the kidneys, while eGFR refers to the number calculated to estimate GFR. 

Measurement 

The main difference between GFR and eGFR is that GFR can be measured by plasma or urinary clearance of creatinine, while eGFR can be calculated from a single blood test result such as serum creatinine. 

Easiness of the Measurement 

The determination of GFR requires both serum and plasma levels of creatinine, while the calculation of eGFR only requires a single blood test result. Hence, this is another difference between GFR and eGFR.

Importance 

Moreover, GFR is important to evaluate kidney function, while eGFR gives a calculated value of GFR. 

Conclusion 

GFR is the glomerular filtration rate that provides an idea about the filtering function of the kidney. Therefore, an ideal filtration marker can be used to determine GFR. Moreover, GFR is important to diagnose many disease conditions associated with the kidney, including chronic kidney disease. On the other hand, eGFR is the estimated GFR, which represents GFR by means of a calculated value. Also, a single blood test result is required for this calculation. Here, the mainly used parameter is the serum creatinine level. Therefore, the main difference between GFR and eGFR is the method of measurement. 

References:

1. “Renal Function.” Wikipedia, Wikimedia Foundation, 11 June 2019, Available Here.
2. “Estimated Glomerular Filtration Rate (EGFR).” National Kidney Foundation, 15 Jan. 2019, Available Here.

Image Courtesy:

1. “Physiology of Nephron” By Madhero88 – Own workReferenceshere (CC BY 3.0) via Commons Wikimedia