The glomerular filtration rate (GFR) is a crucial measure of kidney function, reflecting how well the kidneys filter blood. The estimated GFR (eGFR) is often used in clinical practice to assess kidney health. The CKD-EPI 2021 equation (Chronic Kidney Disease Epidemiology Collaboration), which incorporates both creatinine (CRE) and cystatin C (cysC), provides a more accurate estimation of GFR compared to previous equations.
The CKD-EPI 2021 equation combines serum creatinine and cystatin C levels to estimate GFR. Creatinine is a waste product from muscle metabolism, and its concentration in the blood is influenced by factors such as age, sex, race, and muscle mass. Cystatin C, conversely, is a protein produced by all nucleated cells and less affected by muscle mass and diet, providing an alternative marker for kidney function.
Using both creatinine and cystatin C allows for a more precise GFR estimation, particularly in populations where creatinine alone may be less reliable, such as in the elderly or those with abnormal muscle mass. The CKD-EPI 2021 equation accounts for demographic variables and integrates these two biomarkers to offer a more comprehensive assessment of renal function.
GFR estimation using the CKD-EPI 2021 equation is essential for diagnosing and staging chronic kidney disease (CKD). It helps monitor disease progression, guide treatment decisions, and assess the risk of complications. Regular monitoring of eGFR can detect early kidney damage, enabling timely interventions to slow disease progression and improve outcomes.
In clinical practice, eGFR is used alongside other clinical assessments and laboratory tests to provide a complete picture of kidney health. It is beneficial in adjusting medication dosages, evaluating the need for dialysis, and assessing eligibility for kidney transplantation.
Renal function staging based on eGFR is:
- Category 1: Normal renal function. eGFR ≥ 90 ml/min/1.73m2
- Category 2: Mildly reduced renal function. eGFR 60 – 89 ml/min/1.73m2
- Category 3A: Mildly to moderately decreased renal function. eGFR 40 – 59 ml/min/1.73m2
- Category 3B: Moderately to severely decreased renal function. eGFR 30 – 44 ml/min/1.73m2
- Category 4: Severely decreased renal function. eGFR 15 – 29 ml/min/1.73m2
- Category 5: Very severely decreased or end-stage renal failure. eGFR < 15 ml/min/1.73m2
Despite its advantages, the CKD-EPI 2021 equation has limitations. It may not be as accurate in specific populations, such as those with extreme body sizes, severe malnutrition, or rapidly changing kidney function.
The CKD-EPI 2021 equation for estimating GFR using creatinine and cystatin C is a significant advancement in assessing kidney function. It provides a more accurate and reliable measure of GFR, facilitating better diagnosis, management, and treatment of chronic kidney disease.
