Yes, I agree that eGFR is not really different from the s creatinine. "eGFR" has the patina of units that imply a rate (ml/min) whereas the simple s creatinine has the units of a concentration (mg/dl). And rates would seem more useful than mere concentrations.
But eGFR is not a rate, it is a number derived from the s creatinine.
As clinicians attempt to bridge the communication gap with patients, labs could help by listing the value with a confidence interval or at least a +/- 30%. Like, when my wife says that I didn't clean the dishes well, I point out that 90% of the dishes were quite clean and yes, a chunk of oatmeal may have been left on one plate and one of the plates still smells like egg. This makes her assessment incorrect. Though I've never managed to convince her of this. I hope I have better luck with my online friends, here.
I see this as a semantic issue. eGFR is the same thing as Creatinine. It is simply a formula that tries to normalize creatininr for “the individual”. They could just change the name from eGFR to “normalized creatinine”.
Thx for your comment. At least we (all of us) should remember that the "e" stands for estimate. Note the statistics, and the P30 metric. We are accepting an estimate that is as much as 30% inaccurate. It's an estimate.
I think the EGF should be completely abolished. I was the practicing the nephrologist for 40 years and saw the implementation of this to mine for chronic renal insufficiency.,which increased the payments from Medicare with a classification of renal disease according to severity. Also causes terrible anxiety amongst patients and physicians who do not understand. The start of the avarice of data mininb.
Yes, I agree with your statement. To which I add that a recent meat meal will temporarily elevate one's serum creatinine level. Regarding cystatin C, it could be a better marker of renal function but might be affected by inflammatory states and also states of high cortisol.
My main point is that the "e" in eGFR stands for estimate.
Thanks for this, Dr. Cohen. My understanding is that eGFR is also typically calculated from creatine levels which vary according to muscle mass. If you have a high muscle mass for your BSA creatine estimated eGFR will be underestimated. Vice versa, low muscle mass for BSA and eGFR overestimated.
Supplementing with creatine also effects the eGFR and kidney function better estimated by Cystatin-C eGFR for these two circumstances
And the use of the 1.73m^2 to index the eGFR to body surface area creates a further drop in the reported eGFR. Last week, a patient was worried about his eGFR of 58 ml/min. De-indexing to his actual BSA yielded an eGFR of 75 ml/min.
Removing the race coefficient (because “race is a social construct”) is a denial of physiologic differences, and may have unintended consequences. Same with M/F “normals” for Hgb/Hct.
another article about pk around creatinine - lots of variables ~ I am a nerdy PharmD who loves kinetics and when I worked in the hospital this was always an issue!
discussion on new fda guidance linked here does a good job of talking about issues with GFR and the fda is recommending the Non race based older version fyi .
Or at least have a comment explaining creatinine has a half life like any substance which changes in acute renal failure and makes the formula basically irrelevant At 30ml/min 1/2 life is 16 hrs so it would take 80 hrs to get to an accurate creatinine with any change that represented CrCl ( and thats if it was not still changing and/or increasing its metabolism pathways)
I joke with my colleagues that eGFR was invented to get more business for Nephrologists. I can’t tell you how many elderly patients I see that are now followed by a Nephrologist because of a mildly abnormal eGFR. I have to reassure them that it’s extremely unlikely they will ever end up on dialysis.
Thank you for this article. My eGFR is 79, a "mild decrease" according to the interpretation in the lab work. When I asked both the cardiologist and my internist if I should be worried, they said "no". I am a smaller woman - maybe this value is incorrect. However, it is included in one of the Cardiac Risk Score measurements, and it increases my risk. If this is not being reported correctly, why even include it?
Also, is there no way to include the patient's BSA with the lab work, so a more accurate eGFR can be calculated?
Yes, I agree that eGFR is not really different from the s creatinine. "eGFR" has the patina of units that imply a rate (ml/min) whereas the simple s creatinine has the units of a concentration (mg/dl). And rates would seem more useful than mere concentrations.
But eGFR is not a rate, it is a number derived from the s creatinine.
As clinicians attempt to bridge the communication gap with patients, labs could help by listing the value with a confidence interval or at least a +/- 30%. Like, when my wife says that I didn't clean the dishes well, I point out that 90% of the dishes were quite clean and yes, a chunk of oatmeal may have been left on one plate and one of the plates still smells like egg. This makes her assessment incorrect. Though I've never managed to convince her of this. I hope I have better luck with my online friends, here.
I see this as a semantic issue. eGFR is the same thing as Creatinine. It is simply a formula that tries to normalize creatininr for “the individual”. They could just change the name from eGFR to “normalized creatinine”.
Thx for your comment. At least we (all of us) should remember that the "e" stands for estimate. Note the statistics, and the P30 metric. We are accepting an estimate that is as much as 30% inaccurate. It's an estimate.
I think the EGF should be completely abolished. I was the practicing the nephrologist for 40 years and saw the implementation of this to mine for chronic renal insufficiency.,which increased the payments from Medicare with a classification of renal disease according to severity. Also causes terrible anxiety amongst patients and physicians who do not understand. The start of the avarice of data mininb.
Yes, I agree with your statement. To which I add that a recent meat meal will temporarily elevate one's serum creatinine level. Regarding cystatin C, it could be a better marker of renal function but might be affected by inflammatory states and also states of high cortisol.
My main point is that the "e" in eGFR stands for estimate.
Thanks for this, Dr. Cohen. My understanding is that eGFR is also typically calculated from creatine levels which vary according to muscle mass. If you have a high muscle mass for your BSA creatine estimated eGFR will be underestimated. Vice versa, low muscle mass for BSA and eGFR overestimated.
Supplementing with creatine also effects the eGFR and kidney function better estimated by Cystatin-C eGFR for these two circumstances
Do you agree?
I have found most patients and even some/many clinicians also forget eGFR is measured in ml/min, and not as a %.
And the use of the 1.73m^2 to index the eGFR to body surface area creates a further drop in the reported eGFR. Last week, a patient was worried about his eGFR of 58 ml/min. De-indexing to his actual BSA yielded an eGFR of 75 ml/min.
I agree. But I wanted to be brief and cover the essential point that "e" stands for estimate.
Removing the race coefficient (because “race is a social construct”) is a denial of physiologic differences, and may have unintended consequences. Same with M/F “normals” for Hgb/Hct.
https://pmc.ncbi.nlm.nih.gov/articles/PMC11970497/pdf/apb-14-745.pdf
another article about pk around creatinine - lots of variables ~ I am a nerdy PharmD who loves kinetics and when I worked in the hospital this was always an issue!
https://substack.com/@andrea347517/note/c-212549918?r=7wjbv&utm_medium=ios&utm_source=notes-share-action
discussion on new fda guidance linked here does a good job of talking about issues with GFR and the fda is recommending the Non race based older version fyi .
Or at least have a comment explaining creatinine has a half life like any substance which changes in acute renal failure and makes the formula basically irrelevant At 30ml/min 1/2 life is 16 hrs so it would take 80 hrs to get to an accurate creatinine with any change that represented CrCl ( and thats if it was not still changing and/or increasing its metabolism pathways)
I joke with my colleagues that eGFR was invented to get more business for Nephrologists. I can’t tell you how many elderly patients I see that are now followed by a Nephrologist because of a mildly abnormal eGFR. I have to reassure them that it’s extremely unlikely they will ever end up on dialysis.
Thank you for this article. My eGFR is 79, a "mild decrease" according to the interpretation in the lab work. When I asked both the cardiologist and my internist if I should be worried, they said "no". I am a smaller woman - maybe this value is incorrect. However, it is included in one of the Cardiac Risk Score measurements, and it increases my risk. If this is not being reported correctly, why even include it?
Also, is there no way to include the patient's BSA with the lab work, so a more accurate eGFR can be calculated?