eGFR - different calculations, different results

[Transalp]

I'm sure the old lags here know all about this and doubtless there is data about it kicking around, but it might help some newbies wondering about their variable eGFR results.

The eGFR is predominantly calculated from your blood creatinine, age, sex etc using an equation, but the equation has changed over the years, which gives slightly different results.

We have:

MDRD equation from 1999

CKD-EPI equation from 2009

CKD-EPI equation from 2021

The reason I bring it up is my NHS lab results of today - they are still using the 2009 calculation (per NICE guidelines as apparently Brits are different than Americans), which doesn't compare directly to recent private tests who were using the newer 2021 calculation.

My result today is an eGFR (2009) of 75, however if they had used the older MDRD equation it would have been 70, or if they had used the newer 2021 equation it would have been 80. Quite a spread.

There is also the CKD-EPI 2021 equation that uses Cystatin-C as well as creatinine, which some think of as more accurate or giving earlier detection - a previous result of mine using the 2021 equation and creatinine-only was eGFR 78, but when the cystatin-C number was added to the equation it came back as eGFR 55. Ouch.

Just for people to be aware when comparing results and trends over the last few years, you really need to try and ensure they are all using the same equation - you can plug your creatinine numbers into these links to check.

mdcalc.com/calc/3939/ckd-ep...

mdcalc.com/calc/76/mdrd-gfr...

[orangecity41 NKF Ambassador]

Thanks for pointing this out. You may not be told of this calculation change by your Doctor

[Momwatcher]

seems to me this is a HUGE detail not to be missed or ignored!!!

[Pugsdad]

thank you! I’m going to check them out.

[jflorax]

I'm from Canada, to be honest I don't quite understand the calculations rattling about either.

[Nephrodoc]

Your results are a great example of how inaccurate these formulas are for any given patient.

So none of the formulas are better for any individual. In these ranges of eGFR you may not have CKD if you have no albuminuria

[Transalp in reply to Nephrodoc]

Well my ACR is 2.5 (US units) (0.3 UK units), so that's not bad. That said I have had several lab results with eGFR in the 50's and early 60's.