Discrepancies in INR between Coaguchek XS and Lab

[KLS39]

Pellicle is right - if I had an On-X, I would STILL have a target of around 3.0. Even at 4.0, if your INR ever gets this high, living with it is no big deal. You may wind up with more bruises if you bang yourself than you might with a lower INR, but, really, it's not a big deal.

Now - regarding CoaguChek and Coag-Sense -- I find that you need a bigger drop of blood to fill the transfer tube for the Coag-Sense than you will if you just put your finger with the blood drop on the side of a CoaguChek strip and HOLD it there until the strip draws in all the blood. With a little practice, the CoaguChek may be easier than the Coag-Sense.

To get a good drop, I often hold my hand under warm/hot water for a few seconds. I sometimes swing my arm around - like a windmill - it brings the blood to the hand. I also try to not use the same finger all the time - I find that more 'virgin' areas in other fingers are less scarred and more easily yield usable drops.

I also do a thing, similar to Pellicle's rubber band or dental floss: when I'm waiting for the meter to be ready to test, I compress my finger, below the knuckle, and it usually pools enough blood in the front of the finger to give me a good drop for testing.

It's easier to stay within the fifteen second limit when I use the CoaguChek than it is with the Coag-Sense, because it takes a few seconds for the Coag-Sense transfer tube to fill with blood, and then another second or two (depending on how good your aim is) to transfer the blood onto the strip.

Thanks for the reply. I do switch fingers and I am going to work on the rubber band trick. It's frustrating because after I collect in the tube, and I struggle to get that drop, I am then bleeding perfectly well. Unfortunately, I didn't choose which machine to have, my doctor's office or insurance did. I will master it soon!

 

[Warrick]

Hi just another thing I have noticed when testing if I am a bit dehydrated it seems to make getting a good drop harder.
Ive stabbed multiple fingers to get a good drop and yep then they all start bleeding when its too late lol

 

[pellicle]

Again, I appreciate all your input. I actually received information in the mail from On-X that said the target INR range is 1.5 - 2.0.

you're correct, I just checked and its been revised to 1.5
https://www.onxlti.com/wp-content/uploads/2020/12/01012277E.pdf
sorry I'm out of date on that

Lots to discuss at my next appointment with my cardiologist.

agreed ... print this study out

https://jamanetwork.com/journals/jamainternalmedicine/fullarticle/415179
and ask him about this graph (which I have taken from that study and annotated to make it clear)

and ask about long term accumulation of thrombosis materials on the valve surface and how dips low in INR can cause over time growths of that thrombosis material.

I have the ATS valve which is essentially similar to the On-X but without the marketing department going mad on claims which at best are slightly twisted in their claim and at worst ignore some fundamental facts.

A proper critical evaluation of their claims are prudent:

• The only aortic mechanical heart valve FDA and CE approved with less warfarin1,*
• >60% reduction in bleeding2
• No increase in thromboembolism (TE)2

they don't provide a link for 2 so here it is
https://pubmed.ncbi.nlm.nih.gov/29903344/
but the devil is in the details not the abstract.

Best Wishes

 

[pellicle]

Ive stabbed multiple fingers to get a good drop and yep then they all start bleeding when its too late

I know what you mean

 

[KLS39]

Hi just another thing I have noticed when testing if I am a bit dehydrated it seems to make getting a good drop harder.
Ive stabbed multiple fingers to get a good drop and yep then they all start bleeding when its too late lol

Thanks. That is a really good point. When I was using a lab before testing at home my appointments were usually a bit later in the morning so I had usually had a bit of water to drink. I will be sure to hydrate well before my next test.

 

[pellicle]

Thanks. That is a really good point. When I was using a lab before testing at home my appointments

just a point or two, Warrick does outdoor bloody hard work (which would probably kill many members here), not just sitting around in AirCon, so that's a factor in assessment and secondly lab drawers are usually venepuncture and will always get a sample (except when they miss the vein / go deeper then the vein or otherwise just torture you).

 

[tom in MO]

You don't need to check your INR at the lab. Many if not most cardios do not require it. My group of ~20 cardios does not require it. There is no such thing as a "reference" INR outside of someone who is not taking anti-coagulation and should give an INR of 1. The lab may or may not use a reference method to calculate your INR. They could use the same technology you do at home. You just don't know.

Many studies have shown that in-home testing is superior in keeping someone from having a clot or a serious bleed. That's the outcome of concern, not the actual number. You better believe if home testing leads to problems, we would see the end of it in the litigious USA.

So Superman is correct when he stated: "I just don’t go to the lab. Problem solved. "

 

[carolinemc]

You don't need to check your INR at the lab. Many if not most cardios do not require it. My group of ~20 cardios does not require it. There is no such thing as a "reference" INR outside of someone who is not taking anti-coagulation and should give an INR of 1. The lab may or may not use a reference method to calculate your INR. They could use the same technology you do at home. You just don't know.

Many studies have shown that in-home testing is superior in keeping someone from having a clot or a serious bleed. That's the outcome of concern, not the actual number. You better believe if home testing leads to problems, we would see the end of it in the litigious USA.

So Superman is correct when he stated: "I just don’t go to the lab. Problem solved. "

My cardio requires that I do protime, and the lab uses the same as the home device. I have no home device, so I go to the lab. Limited income and Medicare does not cover the machine nor the strips. I have no problem in going to the hospital lab, for it is easier for me to go there. I get the results within minutes and we calculate the dosage.

 

[pellicle]

My cardio requires that I do protime

say what?

prothrombin time ... really? Like is your cardio unaware of the reasons we moved away from PT to INR?

 

[Warrick]

I thought it was a bit like grams and kilograms being the same thing just different units errr sorta... um... yea.........
PT of 11 to 13.5 seconds
same as INR of 0.8 to 1.1
I know the XS can give the results in PT if you want, not that I do , the difference between say 1.8 and 2.4 is a bit more obvious to me than um 12 ish seconds +11 seconds (INR 1.8ish) and ah um... calculator...

 

[Jamey T]

This is only my opinion, and I have absolutely ZERO facts to back up my claim. But. My claim is I think there is something about some peoples blood that the Coagucheck doesn't like and makes the meter give high readings. I had the same type of results you did. The higher my venous INR, the higher the error with my home unit. That being said, the closer to 1 my INR was, the more accurate the meter was. I even had my wife check one time, and she tested 1.0, which it should have.

I know it isn't liked, but the most accurate meter I had was the InRatio 2. I now have a Coag-Sense and it is much more accurate than my Coagucheck for me. I have bought all of these out of pocket so I can use whatever I choose.

Something else that has been brought up, is the accuracy of the lab, even with a blood draw. I was testing at my local clinic, and my results were suddenly much higher than my Coag-Sense. Enough where my doctor wanted me to reduce my daily dose of warfarin. I have always checked my meters against a blood draw, usually within a half hour and at this time my meter was staying in line with what I thought it should have been. One day after another very high INR reading from a blood draw at my local clinic, I drove to another clinic that was in the same health network a half hour away and the result there was nearly the same as my meter. I brought this to my doctors attention, and they alerted my local clinic. I don't know what happened to cause the difference, but I did learn that even though a blood draw is the "gold standard" they can be inaccurate as well.

Just for information, when I did that test, my meter said I was 2.4, the clinic a half hour away said I was at 2.5, and my local clinic said I was 4.5.

Another thing to note is that I have recorded every INR test I have ever had since my surgery, so I have a history to look back on for my own piece of mind.

 

[pellicle]

Just for information, when I did that test, my meter said I was 2.4, the clinic a half hour away said I was at 2.5, and my local clinic said I was 4.5.

so are you saying that two clinics showed different results by 2.0 INR units from vein draws?

 

[LondonAndy]

Just to add my experience. Here in the UK, at least in two different parts of it where I have lived, us home testers are required to take our meters to our anticoagulation clinic twice a year, for the machine's results to be checked against theirs. In my early days, over 7 years ago, the clinic would do a blood draw that would go off to a lab, but these days the clinic uses the larger, multi-patient version of the CoaguChek meter. So the first point is that the NHS clearly feels confident that these meters provide a sufficiently accurate means of testing INR. (As I have posted ad nauseum, only the CoaguChek devices are approved for use here - see this report).

In all my comparison tests, my CoaguChek result has been between 0.0 and 0.2 different from the lab or their machine, with my machine usually giving the higher reading if there is a difference. By coincidence, today was one of these days to do this check, and results were: my machine 3.0, clinic machine 2.9. I do a test in the clinic at the same time as they do theirs, so there are no time difference issues.

As Pellicle and others have already said: technique is important, particularly that the finger to be pricked is clean and dry, and the drop of blood is applied to the test strip within 15 seconds.

 

[KLS39]

You don't need to check your INR at the lab. Many if not most cardios do not require it. My group of ~20 cardios does not require it. There is no such thing as a "reference" INR outside of someone who is not taking anti-coagulation and should give an INR of 1. The lab may or may not use a reference method to calculate your INR. They could use the same technology you do at home. You just don't know.

My cardiologist requires a lab draw every three months. I went early because I wasn't confident in my technique testing at home. This week I followed all Pellicle's suggestions and was confident in my testing. 1.6 at home and 1.8 at the lab I used for first eight months after surgery. Still working with cardiologist in raising my INR to the top of my goal range.

 

[RAS]

prothrombin time ... really? Like is your cardio unaware of the reasons we moved away from PT to INR?

My cardio requires that I do protime, and the lab uses the same as the home device.

Your cardio means INR. Healthcare providers sometimes use the term "protime" or "PT" when discussing my INR with me even though we are both clearly talking about INR. PT and INR are used interchangeably. PT is the number of seconds to clot and is used to calculate INR. The INR includes calculations to account for variations in devices and test strips such as the type of reagent used or variations in the particular lot that might affect clotting.

In theory two devices that use different reagents should result in the same INR even though they may measure different protimes. Here is a real example showing identical protime and different INRs from my log.

6/28/2010 Device: Hemosense INRatio Protime 30.7 INR 3.1
5/26/2019 Device: Coaguchek XS PT Protime 30.7 INR 2.6

Medicare does not cover the machine nor the strips.

This is not correct. Medicare has covered home INR testing for many years, starting in 2002 for mechanical valves and later expanded to other conditions. See this CMS web page.
Medicare will cover 80% of the cost. If you have a supplemental plan or Medicare Advantage plan, the plan may cover most of the remaining cost. In the US, you would obtain the device and supplies via an INR service that bundles everything into one charge. In other words, you don't pay any upfront cost for the device.
I am not yet on Medicare, but I have seen posts on this forum from members who are on Medicare and paying less than $15/month for weekly testing.

There may be good reasons you don't want to do home testing, but lack of Medicare coverage is not one of them. Someday if you are interested in home testing, I encourage you to look into it. You may have a cost savings as well as more convenience and flexibility.

 

[pellicle]

Your cardio means INR. Healthcare providers sometimes use the term "protime" or "PT" when discussing my INR with me even

with all due respect they may be older and 'out of date' as this has never once happed to me.

Clearly not only YMMV but it appears that it did

Happy New Year

 

[Protimenow]

A few comments:

A few years ago, my rheumatologist took my blood to test my INR. I also tested on the same day. The doctor's lab said my INR was 5.1. I didn't believe it. The doctor said that the lab repeated the test, and got the same result.

I wasn't satisfied with this. I went to two other labs, and got results that were closer to my meter's results.

I told the doctor that the lab was wrong. He thanked me. He told me that he had another patient whose INR has always been in range, and who ALSO had a 5.1 INR reported by the lab. He realized that, on this day, at least, the lab WAS wrong.

I think that he sent the blood for INRs to a different lab.


===

The CoaguChek XS won't give accurate results if, I think, a person's hematocrit is too high (it may be a different blood factor). This is mentioned in the Roche documentation, and the information is available in a variety of places.

When my XS started returning results that I thought were much too high - and were much higher than my Coag-Sense, I asked my doctor to order a panel that confirmed that I didn't have high hematocrit.

About 8 or 9 years ago, I did a lot of testing of the many meters that were available at the time - CoaguChek S and XS, Protime Classic and Protime 3, InRatio (which contributed to a stroke), and Coag-Sys. I also compared these to labs, and to Hemochron - a meter used by my anticoagulation clinic (and that was also used in operating rooms).

At the time, the meter that I trusted the most was the Coag-Sense.

I'm still testing with the Coag-Sense and XS - but I'm running out of strips for both meters. I'll probably continue using both, even though the CoaguChek XS nearly always reports INRs that are higher than the Coag-Sense.

===

One more thing -- I'm lucky to have found a reasonable cardiologist.

Although there's a 'coumadin clinic' in his office, I told him that I've been self-testing and self managing my INR since 2009 - and he told me that I should just keep doing it on my own.

Other doctors wouldn't have trusted me, they may have forced me to use a clinic, and could have been real unpleasant about it.

 

[carolinemc]

Your cardio means INR. Healthcare providers sometimes use the term "protime" or "PT" when discussing my INR with me even though we are both clearly talking about INR. PT and INR are used interchangeably. PT is the number of seconds to clot and is used to calculate INR. The INR includes calculations to account for variations in devices and test strips such as the type of reagent used or variations in the particular lot that might affect clotting.

In theory two devices that use different reagents should result in the same INR even though they may measure different protimes. Here is a real example showing identical protime and different INRs from my log.

6/28/2010 Device: Hemosense INRatio Protime 30.7 INR 3.1
5/26/2019 Device: Coaguchek XS PT Protime 30.7 INR 2.6



This is not correct. Medicare has covered home INR testing for many years, starting in 2002 for mechanical valves and later expanded to other conditions. See this CMS web page.
Medicare will cover 80% of the cost. If you have a supplemental plan or Medicare Advantage plan, the plan may cover most of the remaining cost. In the US, you would obtain the device and supplies via an INR service that bundles everything into one charge. In other words, you don't pay any upfront cost for the device.
I am not yet on Medicare, but I have seen posts on this forum from members who are on Medicare and paying less than $15/month for weekly testing.

There may be good reasons you don't want to do home testing, but lack of Medicare coverage is not one of them. Someday if you are interested in home testing, I encourage you to look into it. You may have a cost savings as well as more convenience and flexibility.

Are you on Medicare? Do you know that Medicare only pays for 80% of anything, and that 20% can mean if a person gets to eat for the month, or get rent paid, or get vital medications? I prefer doing the testing at the hospital. Okay. And I do not have the expensive Medicare Advantage that is ripping us off. Until you are on Medicare, you have no idea what it is like to be on SSDI and limited income. And Regular Medicare does not cover everything. It used to many years ago, but since the 1980's, that has changed and changes every year. Take from one who had a parent on SSDI and living that life now, 20% of any bill is not cheap. Good that you have money. Not all of us do not. Have a nice day.

 

[carolinemc]

say what?

prothrombin time ... really? Like is your cardio unaware of the reasons we moved away from PT to INR?

Protime, INR is the same thing in the USA, we call it and it is the same, no matter the name. Or I have called it blood suckers. Not meant to be funny.

 

[RAS]

Are you on Medicare?

No, but my wife is and I am well acquainted with Medicare and the various supplemental and Advantage plans.

Do you know that Medicare only pays for 80% of anything

Yes I know and stated it in my post which you quoted.


Your comment which I took literally to mean you think Medicare does not cover any INR home testing cost was...

Medicare does not cover the machine nor the strips

... which is what I responded to. I apologize if I misinterpreted that.
For clarification, my point is, you may find the cost for home testing to be more affordable under Medicare than you realize. If you have recently looked into the various companies that provide this service and found that not to be the case, then ok.

I'm just trying to help! Stay positive and have a Happy New Year!