CKD conflicting numbers

[Train1674]

When I go for a routine blood test through my GP, my egfr is always in the 50's all the other numbers are normal, I, e bun,ACR etc, but when I go to see my nephologist every year for the last two, it's in the 70's. Is this just coincidence? Not sure what to make of it, and with the other numbers being ok, not sure if I have CKD or not?

[orangecity41]

Check with Nephrologist and or lab to see which eGFR formula they use.

[Train1674 in reply to orangecity41]

Hi,

I didn't know there were different formulas? Can you explain please?

[orangecity41 in reply to Train1674]

I do not know of the formulae used in Albania for eGFR. If you check with the labs they will be able to advise you what calculation was used. Here is a link to National Kidney Foundation article explaining changes in US, to give you some idea on questions to ask.

kidney.org/newsletter/chang...

[Train1674 in reply to orangecity41]

Haha, I don't know why it says I'm from Albania, I've only just seen that, I'm in the UK. 😂That's why I'm confused as it's all NHS, thanks for the link.

[Marvin8]

My creatinine eGFR is 56. My cystatin-c eGFR is 103. Studies say that these formulas can be off by as much as 30%. This leaves just about all of us (and most nephrologists) guessing, which is why most nephs simply look at the trend in your creatinine and whether or not you're spilling protein in your urine.

[WYOAnne]

My nephrologist always has me go to the same lab each time I have a lab draw. Even then the results can vary. You should discuss the discrepancy with your nephrologist and see what he thinks.

[Train1674]

The thing is I am only booked in to see my nephologist once a year as he just wants to monitor me at this stage, as he thinks I have iga nephropathy. ( This is where my gfr is usually higher.) I get my bloods done at my local hospital every 3 months by my GP. This is where their alway lower, I won't be seeing my nephologist until June 23, hence why I was curious why they were different.

[RickHow]

Bun can easily be different on 2 different dates. It is highly influenced by your hydration level. At one doctor you get egfr of 50's, at another 70's. This too can be highly influenced by hydration. Forget all the numbers you mentioned. If you are concerned about CKD or not simply look at the measurement of your Creatinine level. EGFR measures you Creatinine level. It takes that number and runs it through basically a chart look up for a person of your age, sex, (and older formulas, hardly used any more consider your race). This reports an EGFR. These formulas do NOT consider your Bun, nor ACR, etc. Creatinine is the key.

Now you are seeing a big difference of egfr between two doctors, and probably two different labs. Each lab report will indicate , for each thing tested, what that lab considers to be a normal range. Look and see what each lab considers to be normal. IF the range is the same, but you are getting such a big difference, consistently, of 50 vs 70, something is not right. One lab may have the wrong age for you for example.

Also one lab may be using the standard egfr formula while the other is measuring based upo your Crystaline c level, But again, don't worry about the egfr. Look at your Creatinine level between the two doctors. It can vary a little (for example 1.3 one time, 1.5 another but this would not eplain a 20 point difference in your egfr.

Here is an excellent simple description of Egfr vs ACR vs Bun, etc.

kidney.org/newsletter/what-...

[Hidden in reply to RickHow]

Agree in particular with your comment, "One lab may have the wrong age for you for example."

If I use kidney.org.au/health-profes... and test with two different ages, there is an increase of 17 in the eGFR.

[Train1674]

I know they both have my correct age as I have to confirm all this before the test. If they both use an egfr calculator then I suppose I can get the numbers myself. Are all gfr estimated? ..I find it all confusing, the only number that is adnormal is my creatinine number 123 . Ace is ok, bun is ok, I don't have cystatin c result for some reason.

[Marvin8 in reply to Train1674]

You would have to ask your doctor specifically for a cystatin c test. Just know that creatinine can be thrown off by muscle mass and cystatin c can be thrown off by thyroid problems.

[Angelikafrog]

My nephrologist says there's now a new way to calculate it and my eGFR has suddenly vastly improved. I'm confused

[RickHow in reply to Angelikafrog]

It can get confusing, but here is a summary. The formula most commonly used (a while ago) was to take your Creatinine blood level, your age, your sex, and your race (it did not break it down for all races but simply said white or not white). Then based upon this information it would give you an EGFR. This was the quick, easy, most common way to determine egfr.

Another way existed at the same time that not only did it consider your Creatinine, age, sex, race, but also asked for your height and weight. This produced an EGFR which usually was a few points better than not considering your height and weight (unless of course the person was quite heavy or quite tall. But not many doctors/labs would bother to input the height and weight and this formula was not as well accepted as the first one I described.

Then (I think about 18 months ago or more) it was decided that asking for the race, on simply a white or not white basis was not the best approach. It was FAR too general, there are far too many races in the world to simply say you are white or not white.

The reason for wanting the race information or the height and weight is because the Creatinine level varies dependent upon your build. A person who is larger, or more muscular, will have a higher Creatinine level. Which for their build is normal. Thus the reason they consider your sex. Men are more muscular, have higher Creatinine levels.

There are also other ways, formulas used to consider what your EGFR level but these are the most common.

What your kidney doctor was likely referring to is the change in formula which considered your race, to the formula that no longer considered race. This change was made in 2021. But not all labs converted to the new formula (without race consideration) but now it has become the new normal.

My own doctors do not even pay attention to the egfr at all. Since the formulas are primarily based upon your Creatinine level, they simply measure and monitor the Creatinine. If it is in normal ranges with only minor fluctuations between tests, over time, then that is the best and easiest way to monitor kidney function.

[Train1674]

Hi Rich,

Thanks for that information, that kind of makes sense to me , I'm 90kg and 5,10 and would say I'm quite muscular- 18% body fat. So hence why maybe my creatinine is higher than most,I train most days. My other numbers seem quite normal, but I've heard it's cyststatin c is the true reflection on kidney function for muscular guys but unfortunately it's difficult to get this on the nhs for some reason.

[RickHow in reply to Train1674]

Try the following:

--go to this website, kidney.org/professionals/kd...

--Complete the simple form by entering your Creatinine level (be sure to select if it is mg/dl or umol.

--fill in age

--fill in gender

--Leave the field "standard assays" at the default of "yes"

--FOR THE FIELD MARKED "ADJUST FOR BODY SURFACE", be sure to change it from "no" to "yes". Then it will need you to put in your height and weight.

--Select Calculate and you will get your egfr but this time it will be include being based upon your particular body type.

[Blackknight1989 in reply to Train1674]

You most likely nailed it in your OP just happenstance. Here is why:

This:

How do we measure the performance of a GFR estimating equation?

Estimating equations reflect the best estimate for the population in which they were developed.

However, there can be significant IMPRECISION when using the equation when assessing an individual. The conventional measure of PRECISION has been the P30, which describes the percent of GFR estimates that are within 30% of the measured GFR. Measures of P30 using the same equations vary in different studies depending on the age, muscle mass, and amount of kidney disease prevalent in different population groups that have been investigated.

(Highlights are my addition as is the text below.)

Key to the answer to your question is the “e” = estimated in the lab result of eGFR. The P30 means the measurement is inaccurate by as much as (plus/minus 30%) vis-à-vis mGFR ( measured or the actual value that is too difficult for use as a diagnostic tool because

[Serum creatinine standardization.l Group]

 The group was initially created to review and address the problems related to serum creatinine measurement for estimating GFR, and to prepare recommendations to standardize and improve creatinine measurement. Its work was published in Clinical Chemistry, and updated recommendations can be found on the Creatinine Standardization Program page. The Laboratory Working Group's creatinine standardization work also involved providing information to ensure appropriate dosing for medications that impact kidney function.]

(This, in your case this would need to happen before a result for mGFR. it’s about a 3/4 hour lab work up to calculate mGFR to calculate mGFR. AND since even using this creatinine standardization tool as a value it’s even less accurate versus eGFR. Thus, eGFR can vary as much as plus/minus 30% of an 80% [creatine inaccurate factor] of true mGFR)

(Because of the “e” we should NEVER USE eGFR as a single measure of indication of either worsening or a validation of the benefits of diet modification BECAUSE it is so imprecise and is to be used only as a trend to determine either worsening or stabilizing of kidney function. However, VLPD “believers” are cult-like devote. The unnamed YouTuber ,their televangelist, hocks a modern brand of sneak oil that is a just a protein probiotic unavailable in the West but all over the internet from India for as much as 80% less than his “miracle healing supplement” Yet he is hailed a visionary by his devote when he instead is exploiting those he masquerades as offering his humble help to “cure” [THERE IS NO CURE] their CKD as he did his….disgusting IMHO but he’s an entrepreneur and the worship of his subjects is real!) {But I digress}

(AND THIS)

Why is there more than one GFR estimating equation?

There are several possible (OVER 70) GFR estimating equations currently used to assess kidney function, and each equation has been developed in different study populations. Estimating equations change over time; as new equations are developed and validated in larger populations, older ones become obsolete. For example, the MDRD Study equation has been validated in CKD patients with lower levels of GFR who were predominantly Caucasian, non-diabetic, and did not have a kidney transplant. The MDRD equation has not been validated in children less than 18 years of age, pregnant women, the elderly above the age of 85, or in some racial or ethnic subgroups such as Hispanics. The CKD-EPI equation has been validated in a broader group of persons consisting of predominately Caucasians and Blacks with and without kidney diseases, diabetes, and solid organ transplants who had a wide range of GFR and ages. As a result, CKD-EPI appears to offer some improvement for eGFR between 60 and 120 mL/min/1.73m.

Finally this:

Recommended eGFR equations will be changing. Once guidance is adopted, we will update this content accordingly.

(Clear as mud?!? Lol!)

OH source is niddk.gov and I usually only post the link but this info is on about 10 pages so my typical novel but not a slew of links to unneeded information. Nonetheless here is the link:

niddk.nih.gov/research-fund...

[Train1674]

That was a bit overwhelming , but I got your drift. I suppose the main things is just keep on track with it all.cheers

[Blackknight1989]

Yea I do that sometimes so I apologize. It starts out so well in my head but goes to sh^+ in the execution. My entire point to you was so simple in the point I could have just not bothered you with it. I went back and read that long-winded crap answer to your simple question I posted, maybe my emotional support dog slipped me some new-fangled, mind-altering drugs cause I wrote that crap post and it makes no sense to me. What I wanted to just agree with you on, always remember your labs are a spot in time “snapshot” of your various organ functions and other life sustaining interactions within your body. As we age labs can vary sometimes greatly and certainly much more than when we were younger and healthier. I with the limited amount of information you shared and remembering we don’t and really should never offer a diagnosis, I don’t think you need to worry about anything. In fact I bet you are healthy at least regards CKD. No need to add worry to your life especially regards CKD. Unless labs indicate a worsening of the CKD specific labs I’d run away from this section of the forum and me…lol! I have no idea what I meant in my previous post. My apologies, it was morning 5 with no sleep. Happens to me sometimes now that I’m an old man! My best in your continued good health!

[Train1674]

No worries my friend a reply is better than no reply at all, everyone here is on the same boat. Good work