INR difference between lab and my Coagucheck

[Timmay]

Update. Same exact lab that I used last time. Last time the lab registered 0.4 lower. This time they measured exactly as my XS showed (2.4). What that tells me is that THEY are more variable and less consistent than my meters.

I do think it’s a good idea to have a spare meter on hand … even if just to dismiss any anxiety that you might feel about the reliability of a given meter. They are so cheap that it is so so so so worth the small investment to obtain another meter.

 

[Eva]

I’m not planning to talk to the doctor who ordered the blood work, as I don’t plan to stay with him. He just replaced my wonderful caring doctor who just retired. I feel he is one of those who know everything (since he is the doctor) and the patient has to agree with him!
I’m revisiting my new cardiologist at UCLA Westwood next week and I’ll discuss this with him. I’ll take my machine with me in case he’ll repeat the test then. He’s very caring and smart.

 

[Protimenow]

Update. Same exact lab that I used last time. Last time the lab registered 0.4 lower. This time they measured exactly as my XS showed (2.4). What that tells me is that THEY are more variable and less consistent than my meters.

I do think it’s a good idea to have a spare meter on hand … even if just to dismiss any anxiety that you might feel about the reliability of a given meter. They are so cheap that it is so so so so worth the small investment to obtain another meter.

0.4 lower is insignificant.
There is probably no need for a second meter (although I have more than one of the XS and CoagSense meters).

The XS meters are made for a LOT of use -- clinics use them and probably do thousands or tens of thousands of tests each year. The manufacturer can't afford to have these meters make errors.

The difference made by your lab may relate to changing reagents -- the makers of the reagents make a reasonable guess at the value.

 

[Protimenow]

I’m not planning to talk to the doctor who ordered the blood work, as I don’t plan to stay with him. He just replaced my wonderful caring doctor who just retired. I feel he is one of those who know everything (since he is the doctor) and the patient has to agree with him!
I’m revisiting my new cardiologist at UCLA Westwood next week and I’ll discuss this with him. I’ll take my machine with me in case he’ll repeat the test then. He’s very caring and smart.

Your new cardiologist may be pretty clueless about test accuracy and INR management.

My PCP (or his lab tech) convinced a patient to stop using an XS because it was 'inaccurate.' The doctor probably expected an exact match to blood draw results. The idea of 'accuracy' shouldn't have been applied to INR testing. (I'm assuming that the meter wasn't actually way off lab results).

 

[Timmay]

0.4 lower is insignificant.
There is probably no need for a second meter (although I have more than one of the XS and CoagSense meters).

The XS meters are made for a LOT of use -- clinics use them and probably do thousands or tens of thousands of tests each year. The manufacturer can't afford to have these meters make errors.

The difference made by your lab may relate to changing reagents -- the makers of the reagents make a reasonable guess at the value.

I know that you say 0.4 is insignificant, but I, personally, don’t agree.

What if you’re one of those people following the On-X lower INR recommendation and you’re only using a clinic? Contrary to what we do here on this forum, the majority of people here in the USA use the Coumadin Clinic.

In this case 0.4 is not insignificant. If the lab showed 1.7 (within On-X range) and your INR was really 1.3. That’s horrible. That’s significant in my book.

Same is true in cases where a lab would measure 2.1 but you’re actually 1.7. Over the course of that 1 month (Coumadin Clinic) you’d be out of range and potentially start forming clots.

JMHO.

 

[Protimenow]

I stand corrected. I was thinking more about tests with higher values -- 2.6 vs. 2.2 or 3.0 -- not 1.7 vs. 1.3 or 2.1. Yes, with lower values, 0.4 is DEFINIITELY significant.

One more thing that you mentioned -- if your 'coumadin clinic' only teste monthly, it is putting you at serious risk. If you're comfortable with a 'clinic' that's comfortable with monthly testing, I would insist on weekly testing, find another clinic, or, even better, start self testing and self management (if you're willing to do this).

Pellicle is undoubtedly the best suited to advise you about dosing management.

 

[ATHENS1964]

1

I know that you say 0.4 is insignificant, but I, personally, don’t agree.

What if you’re one of those people following the On-X lower INR recommendation and you’re only using a clinic? Contrary to what we do here on this forum, the majority of people here in the USA use the Coumadin Clinic.

In this case 0.4 is not insignificant. If the lab showed 1.7 (within On-X range) and your INR was really 1.3. That’s horrible. That’s significant in my book.

Same is true in cases where a lab would measure 2.1 but you’re actually 1.7. Over the course of that 1 month (Coumadin Clinic) you’d be out of range and potentially start forming clots.

JMHO.

INR 1.3 +30% =1.7 difference 0.4 ΙNR 3.1+13% =3.5 difference 0.4
a difference of 0.4 units does not exist at such a low INR, 0.4 exists when the inrrange is 3.5 and the laboratory is 3.1, a difference of 13%. As is known, the higher the value given by the inrrange, the greater is the difference with the laboratory. To be calculated percentages and not numbers

 

[Protimenow]

1

INR 1.3 +30% =1.7 difference 0.4 ΙNR 3.1+13% =3.5 difference 0.4
a difference of 0.4 units does not exist at such a low INR, 0.4 exists when the inrrange is 3.5 and the laboratory is 3.1, a difference of 13%. As is known, the higher the value given by the inrrange, the greater is the difference with the laboratory. To be calculated percentages and not numbers

A difference of less than 20% is considered to be accurate, according to the WHO (or another agency, I'm not sure which). So, a difference of 0.4 doesn't (can't) happen at lower INRs.

At higher INRs loses significance the higher the INR is.

And, yes, it's been well documented that the higher the INR reported, the larger the difference from the lab results becomes.

 

[pellicle]

Hi

Pellicle is undoubtedly the best suited to advise you about dosing management.

that's very kind of you to say, but in my view quite a many mech valvers here have become pretty proficient at managing their own INR. Its something that almost everyone (who wants to) does by simply starting with the fact that they are released from hospital on an established dose. All that one then needs to do is

1. measure INR
2. if not in range adjust
3. repeat 1

we even have an entire sub thread for this and discussions of "what should I do"

https://www.valvereplacement.org/forums/home-anticoagulation-monitoring.25/
The most I add is a system which takes it from "gut feel" (or a personally developed heuristic) into something which advises and provides a dashboard of warnings to guide and inform you.

That, and I think so far I'm the only one here who actually steps up and says to newbies "I'll show you the ropes". Its actually no big deal but I don't see anyone else doing it.

Perhaps that's because everyone only has a heuristic which works for them and I've developed a system which is generalisable.

 

[ATHENS1964]

Hi


that's very kind of you to say, but in my view quite a many mech valvers here have become pretty proficient at managing their own INR. Its something that almost everyone (who wants to) does by simply starting with the fact that they are released from hospital on an established dose. All that one then needs to do is

1. measure INR
2. if not in range adjust
3. repeat 1

we even have an entire sub thread for this and discussions of "what should I do"

https://www.valvereplacement.org/forums/home-anticoagulation-monitoring.25/
The most I add is a system which takes it from "gut feel" (or a personally developed heuristic) into something which advises and provides a dashboard of warnings to guide and inform you.

That, and I think so far I'm the only one here who actually steps up and says to newbies "I'll show you the ropes". Its actually no big deal but I don't see anyone else doing it.

Perhaps that's because everyone only has a heuristic which works for them and I've developed a system which is generalisable.

The most important is 2 if not in range adjust. Someone needs to know if and how much he will adjust the dosage or the food, then when he will repeat the test.

 

[Protimenow]

Yes, managing INR is fairly easy for those of us who know how to do it. Some newbies don't realize that small changes are needed to hit the desired INR -- I can imagine some newbies making large changes, then wondering why the INR got farther off target. I can expect other newbies to be afraid of starting self management -- this is where a resource like Pellicle can ease their fears.

I'm not sure if all members considering self management will look for the thread(s) that help people to self manage.

FWIW - I would be happy to also assist users to manage their INR.

 

[pellicle]

Good morning

The most important is 2 if not in range adjust.

well no, I think the most important is 1; test. If you aren't testing you have no idea.

However when describing a system with any level of complexity you start with overviews.
Eg that's a car, you drive it with the steering wheel (more details added as needed)

So I started with a simple overview, this one makes more detail about how

the exact specifics of increase and decrease will be largely depenent on you and your specific. Indeed the exact specifics of "trends" in changes are not discussed in this simplification.

This is part of the heuristic I spoke of. To be clear, a heuristic:

I mean both.

1. I have a method that enables someone to discover
2. my method is computational based and uses accumulated data to produce a quantitative assessment of what that adjustment should be. Of course its not accurate to high levels of precision because nothing in INR is or can be "high levels of precision

Someone needs to know if and how much he will adjust the dosage or the food, then when he will repeat the test.

personally I have never once seen anyone demonstrate in a proper repeatable manner the influence of foods over INR other than for toxins such as found in Grapefruit.

Even cases where someone says "its the fish oil" I don't think it was systematically tested.

I've spent months doing this to myself and while at first I suspected things found that did not bear repeated testing scrutiny.

Even if you did find that (say) spinach caused a shift in INR by X I've never seen anyone (else) present a method to or in any way work out in a quantitative manner how much to adjust by.

YMMV

HTH

 

[Madeleine]

I have had the same experience recently.
My home INR kit is an 11 year old CoaguChek XS and I have twice got a 0.6 difference, last one was 3.8 on my machine and 3.2 on the lab. I was told its either the machine or the strips, but being impatient and deciding that perhaps my 11 year old machine might need replacing, I bought a CoaguChek INRange. My new machine is 0.2 higher than my old machine, and the strips they provided are reading the same as my old strips.
Do you think it is worth downloading new firmware?

My problem is that my hospital are now insisting that I go in for blood tests because my INR readings are more than 0.5 than the lab. Which is not why I have a CoaguChek (or two).

 

[LondonAndy]

I have had the same experience recently.
My home INR kit is an 11 year old CoaguChek XS and I have twice got a 0.6 difference, last one was 3.8 on my machine and 3.2 on the lab. I was told its either the machine or the strips, but being impatient and deciding that perhaps my 11 year old machine might need replacing, I bought a CoaguChek INRange. My new machine is 0.2 higher than my old machine, and the strips they provided are reading the same as my old strips.
Do you think it is worth downloading new firmware?

My problem is that my hospital are now insisting that I go in for blood tests because my INR readings are more than 0.5 than the lab. Which is not why I have a CoaguChek (or two).

If it was me, I would take both my machines into the hospital clinic and do a test on each machine (getting a fresh drop of blood from a different finger for each) in front of them, so that you can show (a) your technique and (b) their results, and then they can compare those with the lab when they get them back. (Or do they do their test on the multi-patient version of the CoaguChek? If so, better still: it's all instant!).

If your two machines are similar to each other, and their lab result is still different, then I think you have a strong argument for getting their lab to do an audit and check there are no out-of-date reagents etc in their system. If your two machines are within 0.2 of each other then I think you have a strong argument that you have sufficiently accurate results to rely on them.

 

[tom in MO]

If it was me, I would take both my machines into the hospital clinic and do a test on each machine (getting a fresh drop of blood from a different finger for each) in front of them, so that you can show (a) your technique and (b) their results, and then they can compare those with the lab when they get them back. (Or do they do their test on the multi-patient version of the CoaguChek? If so, better still: it's all instant!).

If your two machines are similar to each other, and their lab result is still different, then I think you have a strong argument for getting their lab to do an audit and check there are no out-of-date reagents etc in their system. If your two machines are within 0.2 of each other then I think you have a strong argument that you have sufficiently accurate results to rely on them.

I work in measurement and testing. I've had experiences where two measurement devices agree but not with a third. Sometimes it turns out the two that agree are wrong. I believe for INR testing the "gold reference standard" is a blood draw and laboratory test.

 

[LondonAndy]

I work in measurement and testing. I've had experiences where two measurement devices agree but not with a third. Sometimes it turns out the two that agree are wrong. I believe for INR testing the "gold reference standard" is a blood draw and laboratory test.

In the UK, our National Institute of Clinical Excellence recommends the use of the CoaguChek device because of its reliability and sufficient accuracy. Indeed, many clinical settings now use the multi-patient version of the device, as I alluded to in my previous reply. If two such machines are giving similar results it is clearly worth (a) ensuring the patient is using them properly and (b) the lab's processes are validated.

 

[pellicle]

Do you think it is worth downloading new firmware?

no, but then its not expensive.

if it bricks your INRange you still have your Coaguchek XS there as a backup while Roche is dealing with warranty

FWIW I am of the view that its likely that the error lies with the lab

Best Wishes

 

[pellicle]

I believe for INR testing the "gold reference standard" is a blood draw and laboratory test.

I believe that the gold reference standard requires a lab that takes reference standards to heart ... such a lab would be typical of a research facility, but not a commercial lab that churns it out. They may even use a machine like an iStat or a Stago

https://fritsmafactor.com/ptinr-i-stat/
his expressed opinion flies in the face of many detailed studies on it which would not substantiate his opinion.

 

[Timmay]

I work in measurement and testing. I've had experiences where two measurement devices agree but not with a third. Sometimes it turns out the two that agree are wrong. I believe for INR testing the "gold reference standard" is a blood draw and laboratory test.

I have 3 machines. Three (3). I highly doubt they’re all wrong and the lab is right. Wait. There is no “doubt” anymore. I’ve had another test and this time the lab agreed with my machines. Next time the lab might not. Or it may. Who knows. Just depends on what’s happening at the lab that day and how fresh their stuff is.

 

[pellicle]

I’ve had another test and this time the lab agreed with my machines.

but you need to have used the same strip ... I'll lend you my time machine, but you have to promise not to use is for anything nefarious...