Last Word on GFR Tests

Well, here we are at the last installment of our series on GFR and how it is used to measure kidney function. We've looked at 3 different methods the GFR may be estimated. So to close this series, I would like to explain how I learned about the various methods and their positives and negatives.

In a clinic visit early during after my kidney transplant, my doctor instructed me to have a nuclear GFR because my creatinine was slightly higher than what she had wanted. So I asked why.

She responded saying that “your creatinine is 1.6,” then after scribbling some numbers on a her prescription pad, “this is about 55.” She later explained that she calculated my GFR via my creatinine using a formula.

She then further explained that the value of 55 isn't exact since the formula generalizes people in certain classes like race and age. And from her experience, a creatinine of 1.6 may really mean a GFR of 30 in some people or 80 in others. And a nuclear GFR was her choice of measure. Hmmm... interesting.

So I went and had the nuclear GFR done and returned when I got the results. She was correct, the nuclear GFR showed a result of 71, which was excellent for a transplant, since we only have one kidney. She was satisfied with the outcome.

One other thing I remembered was her mentioning that another very good method was the 24-hour urine collection, but often enough it gets messed up one way or another because you have to be very diligent. She told me we could do that instead, and told me, “but you'd have to collect every drop for 24 hours, or else it will be inaccurate.” Enough said, I opted for the nuclear GFR.

Related Posts :