Glomeruli are the tiny filters in the kidneys that filter waste from the blood. Glomerular Filtration Rate (GFR) is a test which estimates how much blood passes through the glomeruli each minute.
The commonly used equations to estimate eGFR include Cockraft and Gault (1976), Modification of Diet in Renal Disease (MDRD) (1999) and Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) (2009). It is the implementation of these equations particularly the MDRD that has raised the medical awareness in the diagnosis and management of CKD and its adoption by many guidelines in North America and Europe.
GFR indicates the stage of Chronic Kidney Disease (CKD) of a patient. The lower the eGFR, higher the damage suffered by kidney. Stages of Chronic Kidney Disease based on e GFR is given in the table below:
| Stage | eGFR | Description |
| 1 | More than 90 | Normal GFR w/proteinuria |
| 2 | 60-89 | Age-related decline in GFR w/proteinuria |
| 3A | 45-59 | Low risk of progression to kidney failure |
| 3B | 30-44 | Medium risk of progression to kidney failure |
| 4 | 15-29 | High risk of progression to kidney failure |
| 5 | Less than 15 | Kidney failure |
| 5D/5T | Less than 10 | Dialysis or Transplant |
*Because of greater cardiovascular disease risk and risk of disease progression at lower eGFRs, CKD Stage 3, is sub-divided into Stages 3A (45–59 mL/min/1.73 m2) and 3B (30–44 mL/min/1.73 m2
. CKD Stage 5 includes patients that may require or are undergoing kidney replacement therapy. Designations 5D and 5T indicate end-stage renal disease patients who undergo chronic dialysis (5D) treatment or have undergone kidney transplantation (5T).
Note: Glomerular filtration rate (GFR) is the total amount of plasma that is ultrafiltered across all the
glomeruli of both the kidneys in unit time. Estimated glomerular filtration rate (eGFR) is a calculated
estimate of the glomerular filtration rate and is therefore also referred to as the calculated GFR.