@windyshores What nephrologists and their associates look for is consistency. In an ideal world, the 2 tests should come close, but that is not always the case. If you are a Mayo patient, they have a pamphlet on the procedure and Iothalamate dye. The nuclear kidney test is not complicated but it involves drinking water, inserting the dye, and emptying your bladder. If you want accuracy of kidney function, this is the best and safe test for most. It also allows the nephrologist to prepare a patient for dialysis or transplant.

Again, you are correct. There are a lot of variables that go into the Creatinine eGFR test, and for that matter, changes may be inconsistent for quarterly testing. Cystatin C is more stable as you suggest, but stability does not equate to accuracy as this nuclear test does.

Last thing about Nsaids, over time you can expect gastric issues including Crohn's disease. Glad you are off that.