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Kidney Diseases

GFR Calc Shows Stage 3- Nephrologist Says No

09/08/2009

Question:

Last year my GFR was 50, a few months ago 53 and 24 hour urine CC test says 59. Creatinine was 1.1 and then upped to 1.2 on CC test. All other Labs look good, no hypertension, diabetes or symptoms. Waited 6 weeks ( a nervous wreck) for Nephrologist appointment via referral. He took about 10 minutes with me and said ....he didn`t think I had CKD. I was shocked. Said he didn`t believe in GFR. He seemed to only care about protein in my urine and had a spot check in the office. I had NO protein...then no CKD he said. Yikes! I`m 60 yrs. I know GFR is an estimate. But, I am puzzled. When I put 1.2 creatinine in the MDRD calc I get 47 GFR. What do you make of this? Have you heard of this happening before? Is the GFR formula that unreliable? That`s scary. Thank you for listening. This has been such an emotional time.

Answer:

The GFR calculator, as you might have noticed, is very sensitive to small changes in serum creatinine and to the methodology used. I don't know what other data that your doctor may have available that would lead him to his conclusion. Perhaps he had other creatinine results that were lower. Perhaps he felt that the other estimates were not done under stable clinical conditions. Remember that if your GFR>60cc/min and there are no renal abnormalities (normal urine analysis) you do not have CKD.

However, if there is certainty that repeated GFR testing yields a GFR<60cc/min, then yes, you have CKD. Remember, your doctor may have wanted to convey a message that you have nothing to worry about. Because you have a normal urine and no hypertension or diabetes then you are not likely to progress to needing dialysis, nor in fact, are you necessarily going to have worsening renal function. If you need more reassurance, then you can ask for repeat studies to be done yearly or switch doctors.

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Response by:

Thomas   Zipp, MD Thomas Zipp, MD
Assistant Professor of Medicine
School of Medicine
Case Western Reserve University