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GFR vs. eGFR

Would someone be so kind as to explain the difference between GFR and eGFR? Also, what is the purpose of Creatinine clearance tests if a GFR has already been established?

Thanks in advance!

GFR is not currently a measurable value, so it's estimated, hence the "e" in eGFR. This is most often done using creatinine clearance because the majority of research into GFR was done using this measurement. MDRD is actually a more accurate means of measuring GFR, but has little research relative to creatinine so fewer drug recommendations are using it, hence it is less often seen. If you ever see "GFR" on a lab slip, read the fine print and it'll say "as estimated by creatinine clearance (or sometimes MDRD)."

I appreciate your speedy reply! Would there be any reason to do a repeat creatinine clearance test after the eGFR results came through a couple days prior?

Glad to help! If you're worried about worsening acute renal failure, or want to establish a trend in renal function, then I'd say repeating a creatinine clearance often is reasonable, hard to say without info on the patient in question

Chronic kidney disease, abscess on leg, hx of DVT. Cr & BUN are high, urine protein is very high, as well as glucose, bacteria, and coarse granular casts

Sounds like the pt has a lot going on kidney-wise. Could be on a nephrotoxic antibiotic? could be a lot of reasons

SierraBravo

Has 3 years experience.

In a hospital setting you will often see daily labs which include a SCr and UN. Looking at the trend will allow you to determine if there is AKI developing or if it already exists, if it is improving. Looking at the SCr/UN is also important for providers because if there is AKI then the patients medications should be renally dosed (if appropriate) to prevent further injury to the kidneys.

Thank you!! That makes a lot of sense.

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