Compare home test with lab

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DachsieMom

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On Saturday, I went to lab around 1030 am to check my INR via a blood test in conjunction with my annual physical labs. I do this about once a year to compare the lab results with my coaguchek. I should have done the home test immediately prior....but it ended up being about 4 hours later. In any event, my lab result was 2.5 and home test was 3.0. I did eat lunch and have a giant coffee drink in between, but I’m concerned they were .5 apart. I’m good with .2 or so but .5 seems like a lot, given my range is 2.3-2.8. The only other thing that could account for the discrepancy is that the prior night, I had wine around 10 pm. I very rarely drink...maybe a few times a year. However, that would increase my inr, so would have made my earlier lab test higher.
I am going to try testing at the lab again in 2 weeks and this time will home test immediately before or after. I will report back 😀.
 

Protimenow

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A four hour gap between one test and the next - even with lunch in between tests - shouldn't make much of a difference. In my experience, CoaguChek XS results are often higher than lab results. In my experience, labs sometimes get it wrong.

However, testing isn't an exact science, and the World Health Organization says that a 20% (and I think up to 30%) variance is acceptable. In this case, although the difference between the two results may look troublesome, if you account for this 20% variance, you shouldn't worry about the difference.

I personally would worry more if either test showed INR at 2.0 or lower.

A retest in a few weeks wouldn't hurt, but you may get a similar difference between meter and lab. (Maybe you should test before you go to the doctor's office this time).
 

pellicle

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On Saturday, I went to lab around 1030 am to check my INR via a blood test in conjunction with my annual physical labs. I do this about once a year to compare the lab results with my coaguchek. I should have done the home test immediately prior....but it ended up being about 4 hours later.
I agree that such a delay shouldn't account for much (even if you were to have IV Vitamin K it takes hours to re-establish normal coagulation.

It could simply be that the lab is using a different reagent to your coaguchek (and are you using any of the strips which are stated to be using the new WHO standards (and is the lab?)

Its vexing, but not really a significant issue (but one would like to know which is closer to correct), as 3.0 isn't much out of range.

Just to ask (not to suggest anything) how did you feel about your own coaguchek sample? Did you feel you got it all in a row, good amount of blood, applied within the 15 seconds of lancing, good location?

If you were interested ask the Lab what standard for INR they use (and which reagents).

Just check your strips against the known recall batches
https://diagnostics.roche.com/us/en/news-listing/2018/roche-diagnostics-to-replace-coaguchek-xs-pt-test-strips.html

additional readings

https://www.medpagetoday.com/cardiology/prevention/76087

https://www.medpagetoday.com/cardiology/prevention/76087
 

jlcsn2015

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On Saturday, I went to lab around 1030 am to check my INR via a blood test in conjunction with my annual physical labs. I do this about once a year to compare the lab results with my coaguchek. I should have done the home test immediately prior....but it ended up being

Hi!, we are all different, but, in my personal experience with Coagucheck and LABS, there is always going to be a little difference as you know, but to make sure "my" machine was OK a couple of years ago when i first encountered something similar to what you experienced i did the following:

1- Phoned Coagucheck Support ( they are VERY good )
2- Told them what had happened
3- They sent me a control kit and asked me to call them when received ( free of charge)
4- Got the kit few days later, they walked me through what to do on the phone and did the test together with me'
5- Result, machine was in order

I have talked to the doctors in my family , 2 sisters, and my family doctor, and they tell me that , yes, INR fluctuates some times but
really really they dont know why....

From what all the doctors mean when they say "not to know", i have come up with a "personal" explanation, could be right could be wrong, and is as follows : "since the liver function is related to mood and emotions" is possible that this factor makes the liver process
warfarin in a different way..." just a thought

I had a AVR with Onx back in 2015 and try to keep my INR at 2, but most of the time is around 2.4,

I was 62 at the time, and sometimes i would like to have made a different choice, but the truth for me remains the fact i dit not want
another OPS in my life, and TAVI yes, is a technique, but i know at least 2 people that when they tried to do TAVI it was not possible and got a second OPS anyways.....

Just a thought, and just sharing my personal experience, there is nothing 100% as we all know

Take care and give them a call, you will be happy to know your test machine is working as it is supposed to

Regards,

J
 

tom in MO

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...The only other thing that could account for the discrepancy is that the prior night, I had wine around 10 pm. I very rarely drink...maybe a few times a year. However, that would increase my inr, so would have made my earlier lab test higher...
Rest easy with your wine, warfarin and alcohol have no known interaction, unless you drink so much you throw-up your warfarin. That comes from my cardiologist and hospital pharmacist.
 

Protimenow

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There's been a bit of conjecture about wine and INR - but you have to drink a LOT of Red Wine (it's apparently the tannins from the skin of the dark grapes), to possibly get a minor effect on your INR.
Consistency, as most of us are aware, is important -- if you drink red wine, drink similar amounts every day (or night), and adjust your dose of warfarin to accommodate any minimal effects from the wine. (What a great argument for drinking wine daily)
 

DachsieMom

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Thanks, all.
It wasn’t a recalled strip. I use coaguchek patient services (for which I pay $101 per month so it better not be a dud strip!). I have been testing for over four years, so don’t think it’s a problem with the sample, either. I have it down by now.... anyway, I will try again. My concern is all of the times when my meter puts me at 2.0-2.5....could be 1.5 to 2 in the lab. Or, the lab could be wrong.
 

pellicle

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Thanks, all.
It wasn’t a recalled strip. I use coaguchek patient services (for which I pay $101 per month so it better not be a dud strip!).
trust, but verify

I have been testing for over four years, so.... My concern is all of the times when my meter puts me at 2.0-2.5....could be 1.5 to 2 in the lab.
so by this what ever your doing is not resulting in problems, so ... no problem right?

Or, the lab could be wrong.
as I say many times this INR stuff is rubbery, it is NOT like measuring the thickness of a piece of steel (well let not get in NASA levels of precision). So that's why its always better than target the middle of the range (and really, don't think about ranges, thin about target INR which for aortic position mechanical is 2.5

Also keep this in mind from a roche publication:
 

DachsieMom

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Update - I took another test. This time, I took the home test 20 minutes prior to the blood draw. Home test was 2.5, blood draw was 2.1. That’s still a big difference (I would expect .2) and I have no clue which is correct.
 

Protimenow

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Whether the lab or the meter were correct, even a 2.1 is safe, although slightly below your desired range. Plus, if you were using a CoaguChek XS, it's not uncommon that their results are a bit higher than the lab results. Also - the difference between the two tests was well within an acceptable margin of error.
 

Jamey T

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I agree that the difference is not that big.
I have recently run into an issue with my closest lab. I had gotten two very high test results in a row, when I had nearly a year of very consistent results comparing my meter to the lab result. When I did the next test, I had done a test at home, immediately went to the closest lab, and then drove 25 minutes to the next closest lab. My test and the farther lab results were in line, and the closest lab I had been using for over 7 years was nearly 1.5 higher than the other two. My doctor agreed with me that the first lab was wrong, and he let them know. I haven't been back to the close lab to see what had happened.
So yes, blood draws are the gold standard, but they can be wrong also.
 

Protimenow

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Hey, Jamey -- you should see the thread that I started - You can't always trust the labs. In it, I mentioned some history of getting bad results, and mentioned a situation a few months ago when a lab gave me a 5.2 - which I suspected was wrong - because my meter gave me 2.9. After getting that wrong result, I did what you did -- I went to two labs to have my INR tested, and I used two meters to get results. My results on the meters were 2.8 and 3.0. Labs provided a somewhat surprising 3.5 and 3.6.

I told my doctor about the erroneous result and he thanked me - another patient's INR was reported to be 7.1. This patient didn't change diet or activity and had a stable INR. My results -and efforts to verify the INR showed that the lab had screwed up - and probably spared that other patient a fair amount of worry.

I'm glad to see that I'm not the only one here who will go out of the way to find an accurate value. (I continue gaining confidence in my meters, versus the frequent errors that I've been getting from labs. I realize that the meter makers have a lot more to lose if the accuracy of their meters or strips is questioned than a lab that does a few INR tests wrong will ever experience.)

One other thing: it shouldn't matter much (if at all) whether you test your blood with a meter 30 minutes, or an hour, or even more before or after a blood draw. INRs don't change that quickly - unless you have a Vitamin K heavy meal quite a while before your other test, or are taking antibiotics and the effects kick in.

It's good to see comparisons with lab results -- mine go back 6 years or more.
 

Protimenow

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Thanks, all.
It wasn’t a recalled strip. I use coaguchek patient services (for which I pay $101 per month so it better not be a dud strip!). I have been testing for over four years, so don’t think it’s a problem with the sample, either. I have it down by now.... anyway, I will try again. My concern is all of the times when my meter puts me at 2.0-2.5....could be 1.5 to 2 in the lab. Or, the lab could be wrong.
$101 a month?!!!
By now, it's clear that you know what you're doing.

For what you're paying, you can own your own meter, buy your own strips, and be ahead of the game in just a few months.

You probably know how to self-manage your INR, based on what you see at this forum, and what modifications the service prescribed. There are people here who can help your with dosing.

I own my meters. The strips cost about $20 a month for weekly testing. The lancing devices are about 25 cents each. DachsieMom - please consider getting your own meter and strips - and saving a LOT of money as time goes on.
 

Protimenow

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In the past, I bought mine on eBay, with the conditions Pellicle listed above. Also, it is also good (usually) to check the seller's rating. One exception - if it was found in stuff from a relative who died, has a long enough expiration date, and the seller will allow you to return it if you're not satisfied (or if the price is so low you want to take a chance), you can also get them from this seller.

For me, so far, the purchase of meters or strips on eBay has been a good one.
 

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