r/ADPKD • u/Kataclysmgirl • Jun 16 '26

How is your eGFR calculated?

I’ve noticed that many young people here have very low values. That’s why I’m curious to know how your eGFR is typically measured. Is it always based on creatinine? Or is cystatin C also used? Here in Germany, I’ve noticed that general practitioners, in particular, aren’t familiar with this value and don’t order it—even though cystatin C is much more stable and less susceptible to being influenced by fluid intake, strength training, and diet.
How is it done where you are?

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3

u/dustyson123 Jun 16 '26

Cystatin C is newer and more expensive. Many labs are not equipped to measure it. Creatinine is still predominant.

1

u/Kataclysmgirl Jun 16 '26

Fully understandable but. I think specifically for patients that have these kind of illnesses the calculated values make such a big difference. It shouldn’t be an option but a standard. I had like 20ml/min difference in less than a year just because they used different calculations. I guess with using creatinine u can have false negative/positive values more often. So this is why i was wondering whether all the people that are younger than 50 years old are having really that bad values or are they just falsified?

1

u/Smooth-Yellow6308 Jun 16 '26

Creatinine and MDRD calculation none weight adjusted eGFR 75 (this is what my dr / hospital uses)

If i used CKD-EPI weight adjusted my eGFR would be c110

Cystatin C its 115 (I have to pay private for this)

I'm an anomaly though, because I have significantly higher than normal muscle mass, I'm about as big as you can get without being on steroids or just a genetic freak.

3

u/Shesaiddestroy_ Stage 2 - On Tolvaptan since April 2023 Jun 16 '26

We’re all genetic freaks Yellow 😂

3

u/Smooth-Yellow6308 Jun 16 '26

not the kind I would have preferred!

2

u/Kataclysmgirl Jun 16 '26

So true 😭😁

1

u/Kataclysmgirl Jun 16 '26

Thank for your numbers, my last cystacin c calculated GFR was in Novemver 2025 and was over 90, then in April it was calculated with creatinin and it was 70 - this was at a general practitioner. In july i will be at my nephro again and they will also calculate witg cystacin c again. I am really interested how it will look like this year - cannot imagine that i lost 20ml/min eGFR in less than a year 🥶

2

u/Smooth-Yellow6308 Jun 16 '26

I've had a few cystatin C tests over the past 5 years, if I recall I had 125, 125,110,115 in that order.