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The estimated glomerular filtration rate (eGFR) provides an assessment of the filtering capacity of the kidney. The eGFR is calculated from a serum creatinine using the CKD EPI equation.2 Aside from the serum creatinine, other variables required for the equation are sex, age, and race. The eGFR has been shown to be more accurate in estimating the glomerular filtration rate than a 24-hour urine collection for creatinine clearance.3 Among patients with chronic kidney disease (CKD), the eGFR is instrumental in determining the stage of disease according to the K/DOQI CKD classification.
Association of Glomerular Filtration Rate (GFR) and Staging of Kidney Disease*
|
GFR (mL/min/1.73 m2) |
With Kidney Damage |
Without Kidney Damage |
|---|---|---|
|
>90 |
Stage one |
Normal |
|
60−89 |
Stage two |
Decreased GFR |
|
30−59 |
Stage three |
Stage three |
|
15−29 |
Stage four |
Stage four |
|
<15 (or dialysis) |
Stage five |
Stage five |
|
*Each stage assumes the associated GFR level has been in effect for at least three months. Stages 1 to 5, with or without kidney disease, indicate chronic kidney disease. Note: Determination of stages one and two (with eGFR >59 mL/minute/1.73 m2) requires estimation of kidney damage for at least three months as defined by structural or functional abnormalities of the kidney, manifested by either: • Pathological abnormalities or • Markers of kidney damage, including abnormalities in the composition of the blood or urine or abnormalities in imaging tests |
||
All estimates of GFR based on serum creatinine will be less accurate for patients at the extremes of muscle mass (including frail elderly, critically ill, or cancer patients), those with unusual diets, and those with conditions associated with reduced secretion or extrarenal elimination of creatinine. Confirmatory tests with exogenous measured GFR or measured creatinine clearance should be performed for people in whom estimates based on serum/plasma/blood creatinine alone may be inaccurate.4
While a normal GFR in young adults is approximately 120−130 mL/minute/1.73 m2, it declines with age, and values <60 mL/minute/1.73 m2 for three months or more is defined as CKD. To determine the presence of proteinuria, low eGFR results may be followed up with albumin:creatinine ratio. An albumin:creatinine ratio >30 mg/g would be indicative of kidney damage.3
1. LabCorp Internal Studies.
2. Levey AS, Stevens LA, Schmid CH, et al, for the CKD-EPI (Chronic Kidney Disease Epidemiology Collaboration). A new equation to estimate glomerular filtration rate. Ann Intern Med. 2009 May 5; 150(9):604-612. Erratum: 2011 Sep 20; 155(6):408. PubMed 19414839
3. National Kidney Foundation. K/DOQI clinical practice guidelines for chronic kidney disease: Evaluation, classification, and stratification. Am J Kidney Dis. 2002 Feb; 39(2 Suppl 1):S1-S266. PubMed 11904577
4. Cockcroft DW, Gault MH. Prediction of creatinine clearance from serum creatinine. Nephron. 1976; 16(1):31-41. PubMed 1244564
