My eGFR fluctuates between high 30s to low 40s. I had labs last week and it was 39 with the "regular" blood draw. But my neph had also ordered a cystatin c with EGFR and that one was 29.
Can anyone tell me the what the difference is, and which is the more reliable. Yes, I will talk to doctor on Monday but would like to know before I go in.
On a side note, labtestsonline seems to be gone. I know they changed their name to testing something or other but not that too seems to be gone. Anyone know anything about that?
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jodaer
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I can try. Last year the KIDGO guidelines changed the recommended eGFR calculation from using creatine to using cyst ain C. New research has found cystain C is a better biomarker for diagnosis and monitoring but using it to calculate eGFR lowers many of our numbers. Several reasons were given specifically the recommendation to include cystain C as opposed to creatine along with several other labs to manage CKD patients . However, it eliminates the race issue in eGFR calculation. You know when we get out labs and there is the eGFR number that says eGFR and then eGFR African-American, well the new test eliminates that issue. Again, it’s not about reliability but just a different test. If you want to investigate the eGFR test and the several different ways to calculate it (prior to the new recommendation over 40) it’ll blow your mind. It is probably one of the most inaccurate blood test that is calculated maybe 8-10 different ways by different labs giving the wide swings many of us see in our reports. Yet it is the KEY measure to determine when and how quickly we will progress to ERSD. Anyway, eGFR calculated with cystain C is the new standard recommended by the KIDGO guidelines and within the next couple of years ALL physicians and labs will be (or should be) using it. Here is a link that explains it:
I can find some additional articles articulating what the switch from creatine to Cystain C means if you like to know. Just read a couple from the same site. Basically Cystain C is a much better indicator of overall kidney function than creatine. Also, Cystain C levels are not influenced by non-kidney factors like creatine is meaning your creatine lab levels can be incorrect due to lifting weights or dehydration etc…Cystain C cannot. Plus there are several issues with creatine (which I can also provide you a couple of links to sites like the NIH’s NIDDK section or MedLine detailing the shortcomings of creatine as a significant predictor of kidney health) and nephrology has been trying to eliminate creatine as a tool used to asses kidney health for the last 5/6 years thus the new eGFR calculation and other changes. Anyway, I’ll stop now as I’m too long-winded most all of the time. If you’d like any of the above mentioned links let me know I’d be happy to provide them. Finally best of luck with the appointment Monday and I’m sure your nephrologist will provide a much better explanation than I…lol! Take care!
Thanks, but that's not necessary. I read a couple of articles on the link you sent yesterday. Grey's Anatomy (i know, TV, but) had an episode on eGFR in re African americans. It shed a lot oflight on the subject.
Also want to say I don't agree with your statement that you get long winded. Your posts are sometime long however the info is always spot on, and you back up your info. So thanks for that too.
No problem Jodaer. I always try to help and by wanting to do that I often over share information that may be irrelevant. I spend a lot of time reading medical studies and sites about our disease. In the past that may have been fruitless but with the advances and innovation coming due to increased attention and funding in the last 5 or so years for CKD there is an avalanche of new information out there beneficial to us. So I like to share it where possible.
Thanks for the kind words made my day! Oh I’m not spot-on see Kidney Coach’s correction below. I appreciate the corrections as well! But seriously thank you!
I believe the correct words are Cystatin-C, Creatinine, KDOQI, or you're meaning KDIGO. I could be wrong, but from my own research and learning I believe this is accurate spelling. Blessings
no you are correct. I appreciate the corrections, I need that often…lol. That’s why I usually provide or offer to provide links cause my text contains the mistakes. Again I appreciate it.
Just in case you were not aware, both Quest and LabCorp offer online lab test ordering. I've used Quest 3 times for my PSA. It's around $69 dollars but I like that better than having to drive across town to see a urologist then have to go back to discuss results.
I get my labs done at Quest. When i see my doc she gives me the lab script for the next time. I go into lab about 2 weeks before next apt. This works really well. I can't afford to pay for lab work esp since my insurance covers them 100%
Maybe but there is still research needed for Cystatin C:
Study Name:
Study of Serum Cystatin C and Serum Creatinine in Different Stages of Chronic Kidney Disease Patients
Quote:
“Conclusion: We found out that both serum creatinine and serum cystatin C were significantly increased across CKD groups but cystatin C is a better predictor of CKD than creatinine in stages with eGFR≥60 ml/min/1.73 m2 as serum cystatin C was found to be raised contrary to serum creatinine which was within normal limits, although in stages with eGFR<60 ml/min/1.73 m2 there was no significant difference between the two. We found out that normal serum creatinine levels during the stage of kidney disease with eGFR≥60 ml/min/1.73 m2 does not necessarily mean normal renal function. Cystatin C should be encouraged as a screening tool for early renal impairment in the patient as the risk of developing CKD, especially in long-standing hypertensive and diabetic patients as an adjunct to creatinine estimation. It should also be included in the management protocol for these patients.
Another: Study name: Traditions and innovations in assessment of glomerular filtration rate using creatinine to cystatin C
Quote:
“Although current methods of estimating GFR have improved in population measures of reliability, all have significant individual-level inaccuracies that can be an issue when clinical decision-making is contingent on the actual level of GFR. Modern methods of GFR measurements should be made widely available to enhance individualized patient decision-making.”
This, many times the Cystatin C method CAN be a more accurate it is primarily used to remove race and body mass from the eGFR calculation. It has an inaccuracy percentage of up to 30% of mGFR.
Finally: Name of Review: The race coefficient in glomerular filtration rate-estimating equations and its removal
Quote: “The race coefficient in glomerular filtration rate-estimating equations and its removal.”
Thus, the Cystatin C eGFR is still an estimate and still has its inadequacies. The difference between the two methods averages about 5 points in those of us with eGFR of < 29. That can be an issue and is almost spot on with me. My nephrologist still uses the Creatinine based equation and I average about 23 at that lab. The VA uses Cystatin C and I am 17.7 there. So 5.3 points. Remember all of these are estimated and need to be taken as a series of measurements used to evaluate the progression of CKD along with other lab values. All of the current eGFR calculation methods average about a 30% difference from mGFR and that is an important issue for both patients and physicians and SHOULD be addressed.
I am not a doctor only a fellow patient trying to be of help. As always I wish you all my best in your CKD journey!
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