Current Clinical Practice
The most common clinical assay for renal function is a serum creatinine blood test, coupled with theoretical equations to yield an estimated Glomerular Filtration Rate (eGFR). A rise in serum creatinine occurs upon kidney injury/insult; yet this resultant estimated GFR based on an instantaneous measurement of serum creatinine is well-known to be a poor surrogate for the true glomerular filtration rate due to the inherent limitations such as:
- Not a sensitive measurement in that a patient can lose up to half their kidney function before an abnormal level of serum creatinine is observed.
- A 24-72 hour delay in the detection of an abnormal serum creatinine level due to kidney injury/insult.
- The influence of age, hydration, muscle mass, and dietary input on serum creatinine levels not related to GFR.
However, this test is widely used due to the very inexpensive cost and is almost always done within a larger blood panel of tests.