Many supplements affect blood test results, and creatinine supplementation is one of them. I always stop creatine and most other supplements at least three days before a blood test. I want to see what my body is doing without props.
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I like to see what my blood is doing with props, but for my USA blood test, I limit the number of supplements I take vs the ones I do in Hong Kong.
My eGFR is steady at about 108 when calculated with Cystatin C.
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Tim
#19
Few things are as satisfying as a good steak. But chicken, tuna, and salmon are more benign. Make at least one day of the week all fruit and vegetables.
My hemoglobin is low, which may indicate an iron deficiency, which may suggest iron tablets, although an iron infusion would be nice.
@ RobTuck
What is your eGFR when you consume normal amounts of protein. Have you crosschecked with a Cystatin-C measurement?
In my one experiment, I binged on two 1 lb. rib eyes. Tested a few days later, my GFR had dropped from 40 to 32. When my kidneys bounce back, as they usually do, I may celebrate with a lamb shank or some pot roast.
I am faithful to the renal diet, but not rigidly so, and my GFR fluctuates. I don’t think I’ve ever had a Cys-c test. I’m not dissatisfied with current arrangements.
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jnorm
#20
The rest of my diet didn’t change much, the increased beef has been replacing shrimp, chicken, and bacon (permanently removing bacon). Fruit as main fiber source, white rice as main carb source, avocados and avocado oil as main source of unsaturated fats. Zero fast food. I eat a lot of ice cream but overall I’d say my diet is good. No NSAIDs.
amuser
#21
Anyone considering a cystatin-c test should get it at Quest, not Labcorp:
And the posts after.
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Rats. I was relying on LabCorp for my Cystatin and other kidney related bios.
In general, and partially based on Matt Kaeberlein’s remarks (he said about LabCorp “do better”), I’m thinking of getting my bloodwork done all by Quest.
My LabCorp Cystatin C was $75 (via Life Extension).
Question: Is it normal for an eGFR test to be jumping around like that? Mine is Ok for my age, not optimal, but has been very steady over the last 15 years, showing a gradual decline but no jumps.
Beth
#24
Fwiw, Gethealthspan just switched from using Labcorp to Quest.
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Any idea why they switched?
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Beth
#26
I don’t, but am curious. I had reached out to them to find out if I could go to quest instead of labcorp, and their reply was simply they had just made the switch.
I have no idea if the test results of one are better than the other, but in my city Quest is a much better experience. Most results are returned in 24 hrs. The ease of scheduling is much better, and I am usually seen within ten minutes of the scheduled time. Also, they have many more locations.
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I don’t have a way to make a technical assessment but have used LabCorp for two decades and am pleased with their logistics, customer service, and from what I can tell, their state of the art analytical equipment. There is no way to be certain but the results I get appear to be congruent with those of Quest in cases where a healthcare system uses them. Their CapX must be high because they continue to add automated analytic capabilities locally which reduces the need to route specialized test samples around the country as al the labs have done in the past and still do to some extent. My biggest two complaints about LabCorp are that they the morning appointments are booked solid for weeks in advance and some lab results can be slow if your test(s) are not common. Routine tests turnround in a day.
These two companies are locked in head-to-head competition so I suppose we will see more changes.
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Yes, some results are delayed up to three weeks, which is ridiculous. But booked solid? I noticed they’re booked online, but if I just show up without an appointment, they take me immediately within literally 3-5 minutes. So that’s what I’ve been doing the last few times. I need to have this on time, because I’m checking sirolimus levels at specific times post dose, like 50 hours, so I need a test at a timeframe that’s within 15-30 minutes of the dose, no more. I walk in, put down my requisition papers, give name, tell 'em I’m paying out of pocket, and have barely enough time to sit down before I’m called in for the draw. I don’t know if this is typical, but that’s how it works at the location I always go to, in Beverly Hills, CA. At most there are like two people in the waiting room. My visits are just before or after 12 noon weekdays.
My other blood tests are at UCLA with doctor’s visits, and they use all sorts of labs when they outsource, including Quest. Frankly, I never gave much thought about the specific facilities - my bad.
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RobTuck
#30
I have only four isolated examples on which to base the waiting issue. In locations I have visited in Arizona, the line runs out to the sidewalk and you see a line of cars with people waiting in them. They text you when you’re next to be up. I would estimate that each phlebotomist processes one person every five minutes and the largest of the three clinics I have visited in Arizona has six bays. The only clinic I use in Idaho has three phlebotomist bays and the same long lines and processing speed. Both places tell me things die down in the afternoon. In Arizona, Quest Labs has partnered with Banner Health branded as Sonora Quest Diagnostics. Most of their facilities are embedded in a medical center. Both Quest and LabCorp offer a mobile service in which a phlebotomist will take samples at your home or place of work. I believe the cost is $50 for local service.
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amuser
#31
The ‘jumping around’ range for Labcorp has been 50%. For Quest, values have come back between 65-75, so range about 15%.
I had blood drawn at labcorp, then walked to the building next door to quest, and had the blood drawn for the same tests. One of the following numbers is not like the others. (Note that the creatinine egfr’s are creatine-influenced.)
I do lots of testing at labcorp and I don’t intend to change to quest because of this one test. And I hate waiting for results, so I put all the overnight-resulted tests on one order, and those that take longer on another. Works.
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You shouldn’t compare eGFRs. You should compare the underlying serum creatinine and serum cystatin c concentrations. They might use different assumptions in the formulas they use to calculate the estimated GFRs from the underlying concentrations. E.g. the kidney foundation one can incorporate age, height, weight, sex, and maybe a few other things to convert the serum concentration of one or both of creatinine and cystatin c into an eGFR.
NB: OP was aware of this and verified the equations were specified the same way at each lab and posted the eGFRs for simplicity.
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amuser
#33
Please critique this post:
My apologies, sir. Your method is beyond reproach.
Inter-lab of 5-10% in the eGFR product are within lab process error terms. Typically it is less than 5%. However, both labs use enzymatic assays (not Jaffe) and may have slightly different reagent and calibration curves. Even small inter-assay variation (e.g. ±0.05 mg/dL) leads to significant changes when values are <1.0 mg/dL, so there is a nonlinearity in the error component that will be reflected in where the person falls on the scale.
Variance greater than 5-10% with identical samples does not occur in repeated certification tests over years. The same is true for Cystatin C but the precise error terms are different.
All labs I am aware of have eliminated the race variable for eGFR but age is in all of the equations as you can see in the current eGFR model:
1. CKD-EPI 2021 Creatinine Equation (eGFRcr)
Equation:
eGFRcr=142×min(Scrκ,1)α×max(Scrκ,1)−1.200×0.9938Age×[1.012 if female]\text{eGFRcr} = 142 \times \min\left(\frac{\text{Scr}}{\kappa}, 1\right)^\alpha \times \max\left(\frac{\text{Scr}}{\kappa}, 1\right)^{-1.200} \times 0.9938^{\text{Age}} \times [1.012\ \text{if female}]eGFRcr=142×min(κScr,1)α×max(κScr,1)−1.200×0.9938Age×[1.012 if female]
Where:
- Scr = serum creatinine (mg/dL)
- κ (kappa) = 0.7 for females, 0.9 for males
- α (alpha) = –0.241 for females, –0.302 for males
- Age in years
- eGFR in mL/min/1.73 m²
- No race coefficient
Ha! That’s a little hard to read, eh? Try this:
