E. Serum urea – Explanation
eGFR variables – CAGE – Creatinine, Age, Gender, Ethnicity
Chronic kidney disease: eGFR and classification
Serum creatinine may not provide an accurate estimate of renal function due to differences in
muscle. For this reason formulas were develop to help estimate the glomerular filtration rate
(estimated GFR or eGFR). The most commonly used formula is the Modification of Diet in Renal
Disease (MDRD) equation, which uses the following
variables:
- serum creatinine
- age
- gender
- ethnicity
Factors which may affect the result
- pregnancy
- muscle mass (e.g. amputees, body-builders)
- eating red meat 12 hours prior to the sample being taken
CKD may be classified according to GFR:
| CKD stage |
GFR range |
| 1 | Greater than 90 ml/min, with some sign of kidney damage on other tests (if all the kidney tests* are normal, there is no CKD) |
| 2 | 60-90 ml/min with some sign of kidney damage (if kidney tests* are normal, there is no CKD) |
| 3a | 45-59 ml/min, a moderate reduction in kidney function |
| 3b | 30-44 ml/min, a moderate reduction in kidney function |
| 4 | 15-29 ml/min, a severe reduction in kidney function |
| 5 | Less than 15 ml/min, established kidney failure – dialysis or a kidney transplant may be needed |
*i.e. normal U&Es and no proteinuria
