Comment by cthalupa

I'm not sure what point you're trying to make here. Have I missed somewhere in the discussion where eGFR equation adjustment based on ethnicity has been discussed?

Creatinine is the standard marker used for eGFR. It is also a byproduct of muscle metabolism. People who regularly lift weights or have lifestyles that otherwise result in a higher-than-normal muscularity will almost universally have higher creatinine levels than those who don't, assuming similar baseline kidney function. It's also problematic for people with extremely low muscle mass, for the opposite reason.

It's one of the reasons enhanced bodybuilders can get bit with failing kidney function - they know that their eGFR is going to look worse and worse based on creatinine formulas so they ignore it, when the elevated blood pressure from all the dbol they're popping is killing their kidneys.

Cystatin C is the better option for people with too much (or too little) muscle for creatinine to be accurate.