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Clinical significance of GFR
The GFR is the generally accepted, best index of kidney function. Chronic kidney disease (CKD) is defined as GFR less than 60 mL/min per 1.73 m 2 as well as markers of kidney damage.
In the United States the most common marker of kidney damage is urine albumin.
Other markers are kidney cysts or pathologic changes in the kidney, for example.
The severity of CKD is also determined by the level of GFR.
The Six Stages of Chronic Kidney Disease Use GFR to Define Severity
CKD Stage | Definition | Description |
---|---|---|
1 | GFR ≥ 90 mL/min per 1.73 m 2 with other signs of kidney disease (usually an abnormal ultrasound or urinalysis) | Normal or high GFR |
2 | Slightly decreased GFR (60–89 mL/min per 1.73 m 2 with other signs of kidney disease | Mildly decreased GFR |
3a | GFR of 45–59 mL/min per 1.73 m 2 | Mildly to moderately decreased GFR |
3b | GFR of 30–44 mL/min per 1.73 m 2 | Moderately to severely decreased GFR |
4 | GFR 15–29 mL/min per 1.73 m 2 | Severely decreased GFR |
5 | GFR < 15 mL/min per 1.73 m 2 | Kidney failure |
CKD , Chronic kidney disease; GFR , glomerular filtration rate
a Once the GFR falls below 60 mL/min the GFR alone is enough to define CKD. in the most recent KDIGO guidelines, CKD stages have been replaced with GFR categories, albuminuria categories, and assessment of the etiology of CKD.
Decreases in GFR are associated with increasing symptoms and metabolic abnormalities. These abnormalities include anemia, acidosis, malnutrition, and bone and mineral disorders.
In addition, medications that are metabolized or excreted by the kidney need to be dose adjusted (or avoided completely) in patients with decreased GFR. Even drugs that are not excreted by the kidneys can have altered pharmacodynamics and pharmacokinetics in the presence of decreased GFR.
Most importantly, a GFR less than 60 mL/min per 1.73 m 2 is associated with complications of CKD, including risk for kidney failure and increased total and cardiovascular disease mortality. For these reasons the GFR is the single number that best expresses kidney function.