You can't always trust the labs

[Protimenow]

I'll summarize this at the beginning, and maybe at the end, of this post.

You can't always trust the lab results. If your INR from the lab is unexpectedly high, or doesn't match your meters, it may be your lab that's wrong.

A case in point: on Monday, I went to the Rheumatologist for an issue with my right elbow. He withdrew 8 ml of blood from an area just above my elbow. He asked if I wanted an INR taken, and I told him to do it.

Two days earlier, using my Coag-Sense PT2, my INR was 3.2.

On Tuesday morning, my Rheumatologist called me tell me that my INR was 5.2. He suggested that I call my primary care physician and might consider taking Vitamin K to lower my INR.

Instead, I decided not to believe the lab results (I've seen errors in my INR at least two times).

I tested a few minutes later, using my Coag-Sense PT2 and my 'classic' Coag-Sense meter. My INR on one meter was 3.0, the other gave me 2.8. If I had CoaguChek XS strips, I probably would have run a test on that meter, too.

I decided to check against other labs. I certainly doubted that my meters, which had always been consistent, were wrong and the lab was right. I went to my primary care office and had a blood draw. Two hours later, I had a blood draw at UCLA. I didn't want to take any chances or shortcuts in getting a true INR value.

The lab results were 3.6 (from UCLA) and 3.5 from my PCP.

I saw the Rheumatologist yesterday to check on my elbow. He asked me what I was doing about my high INR. I told him, bluntly, that the lab was wrong. I told him about the results of two blood draws and two tests on my meters.

Instead of defending the lab, he told me that he was glad to hear that the lab was wrong--he has a patient whose dosing and diet were always consistent, and the lab reported a 7.1. She was coming in for a retest.

A few points here -- if the INR result from the lab seems wrong, it might be -- have the blood retested. I've heard of one clinic that tests using Coag-Sense to validate ALL lab-reported INRs over 4. If your INR results aren't close to the meter's results - it may be the lab.

You can't always trust the labs as being the gold standard -- the blood may have been mishandled between the time it was drawn and the time it got to the lab; an incorrect value for the reagent used by the lab could result in a wrong value; the stuff in the blood collection tubes may be flawed. INR testing is a bit more art than science, because setting a value for the reagents used for the test (meters and labs) involves a bit of educated guessing.

Years ago, when I was using the InRatio and called them about some discrepancies between the INR reported by the InRatio and the lab values, they told me to 'trust the lab.'

I wish I always could.

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Do you have similar horror stories?

 

[ForeverThankful]

In the beginning, before I had meters, I had my blood drawn at a lab in town which I found out sends the blood to a testing facility about 3 hours away. At the time I assumed they would give reliable results but they didn't. I discovered this about 6 weeks after surgery when I passed a kidney stone. I've passed a few kidney stones over the years and this one was small, almost didn't even feel it but my urine was a stream of blood. The lab said my INR was 3.5 which shouldn't have caused the amount of blood we were seeing for passing an almost pain free kidney stone. Sure enough when I had my blood drawn at the hospital my INR was about 5, which made more sense.

After that I ordered a CoaguChek XS and about a month later my insurance sent me another one. So now I have 2 meters. If I test on both meters in the same time period the result is always the same or off by only 0.1. If I want a blood draw I now go to the heart hospital where I had my surgery and the results compared to my meters is never off by more 0.1

During the following months I had my INR tested a few more times at the local lab and compared it to my meters and the hospital lab. In every case the meters and hospital gave similar readings but the local lab readings were way off, usually by 1.0 or more. I trust only my meters and the heart hospital which tests the blood almost immediately after they draw it. At this point any other lab would have to prove itself to me

My personal advice, for what it's worth: never automatically assume that a lab reading is valid.

 

[LondonAndy]

I agree with these posts. I haven't had a lab result problem myself, but it seems to me that there are more things that can potentially go wrong with them than with using a home meter, though of course it is important to use those correctly too, applying sufficient blood and doing so promptly after pricking. Blind faith in professionals is never healthy - if results don't seem right, challenge and retest.

 

[Protimenow]

I went through quite a few months testing meters and labs a few years ago. As I mentioned in other posts, I encountered some lab errors back then, and got some ridiculous dosing advice secondary as a result of the inaccurate tests.

My testing back then showed problems with the InRatio, and results sometimes significantly higher than the lab results in InRatio and CoaguChek XS. It's been well documented that the CoaguChek XS loses accuracy at INRs above 3.5 or so. Perhaps Roche has figured this out and made corrections to adjust to this issue.

Testing may be at a point where we should trust the meter, and be a bit skeptical of the labs -- especially if we get results that are far from those on the meter(s).

 

[LondonAndy]

... It's been well documented that the CoaguChek XS loses accuracy at INRs above 3.5 or so. Perhaps Roche has figured this out and made corrections to adjust to this issue.

Could you point me in the direction of some of those documents? I know that some strips were recalled last year because of potential inaccuracy over 4.5, but I was not aware that there is a wider and general concern about accuracy of the CoaguChek XS above 3.5

 

[carolinemc]

I'll summarize this at the beginning, and maybe at the end, of this post.

You can't always trust the lab results. If your INR from the lab is unexpectedly high, or doesn't match your meters, it may be your lab that's wrong.

A case in point: on Monday, I went to the Rheumatologist for an issue with my right elbow. He withdrew 8 ml of blood from an area just above my elbow. He asked if I wanted an INR taken, and I told him to do it.

Two days earlier, using my Coag-Sense PT2, my INR was 3.2.

On Tuesday morning, my Rheumatologist called me tell me that my INR was 5.2. He suggested that I call my primary care physician and might consider taking Vitamin K to lower my INR.

Instead, I decided not to believe the lab results (I've seen errors in my INR at least two times).

I tested a few minutes later, using my Coag-Sense PT2 and my 'classic' Coag-Sense meter. My INR on one meter was 3.0, the other gave me 2.8. If I had CoaguChek XS strips, I probably would have run a test on that meter, too.

I decided to check against other labs. I certainly doubted that my meters, which had always been consistent, were wrong and the lab was right. I went to my primary care office and had a blood draw. Two hours later, I had a blood draw at UCLA. I didn't want to take any chances or shortcuts in getting a true INR value.

The lab results were 3.6 (from UCLA) and 3.5 from my PCP.

I saw the Rheumatologist yesterday to check on my elbow. He asked me what I was doing about my high INR. I told him, bluntly, that the lab was wrong. I told him about the results of two blood draws and two tests on my meters.

Instead of defending the lab, he told me that he was glad to hear that the lab was wrong--he has a patient whose dosing and diet were always consistent, and the lab reported a 7.1. She was coming in for a retest.

A few points here -- if the INR result from the lab seems wrong, it might be -- have the blood retested. I've heard of one clinic that tests using Coag-Sense to validate ALL lab-reported INRs over 4. If your INR results aren't close to the meter's results - it may be the lab.

You can't always trust the labs as being the gold standard -- the blood may have been mishandled between the time it was drawn and the time it got to the lab; an incorrect value for the reagent used by the lab could result in a wrong value; the stuff in the blood collection tubes may be flawed. INR testing is a bit more art than science, because setting a value for the reagents used for the test (meters and labs) involves a bit of educated guessing.

Years ago, when I was using the InRatio and called them about some discrepancies between the INR reported by the InRatio and the lab values, they told me to 'trust the lab.'

I wish I always could.

--------------------------------------------------------------------------------------
Do you have similar horror stories?

I only get higher numbers of I take in more green leafy vegs, or take an antibiotic for infection, or get too active. I do not home test. But at the new hospital, teaching hospital, they do the test while I am there and we get the numbers within 5 minutes and dose accordingly, which I love. I have been treated better this way than a lab from when I had insurance from working. If the number is a bit high, we try to figure out how and decide on a dosing and retest within a week. Never retest within three or two days, cause the new dose has to have time to adjust in your body. Many horror stories about retesting too soon after new dosing.

Have a great day and thanks for letting me rant. Am an old pro at it, LOL!. Hugs for today.

 

[Protimenow]

Carolinemc -- leafy greens should lower your INR, while the others may raise it. True, retesting for the effects of new doses won't show up in your INR for about 3 days - the half life of warfarin's effects.

In my experience, Vitamin K (the vitamin in dark, leafy vegetables that can affect your clotting ability) showed effects quickly - next day or sooner. If you have a lot of leafy greens, a test the next day should show some effects.

LondonAndy -- the decrease in accuracy of the CoaguChek XS at hither INRs has been written about quite a bit - I'll have to look for papers reporting this (they're out there - we've (not just me) written about the reports a fair amount at this site a few years ago. This issue is not related to the strip recall.

If your INR at a clinic or doctor's office, tested on a CoaguChek XS was above, say, 3.5 or 4, this would explain why they probably ordered a blood draw to confirm it.

 

[tom in MO]

Could you point me in the direction of some of those documents? I know that some strips were recalled last year because of potential inaccuracy over 4.5, but I was not aware that there is a wider and general concern about accuracy of the CoaguChek XS above 3.5

The manual says it reads 0.8 to 8.0, but later on it says for measuring range to check your paperwork with the strips.

There is a paper from 2007:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1860570/

There are no data points above an INR of 4 (Figure 1) but who would let their INR get above 4 just to see if a meter is correct

Also don't blame the labs, maybe the problem was with the blood draw, the container/preservative or the handling of the sample before it got to the lab.

 

[Protimenow]

Yes. I pointed this out in my initial comment.

I can't see anybody intentionally letting the INR go above 4.0 just to test a meter or lab's accuracy. But it DOES happen. Antibiotics can raise the INR by killing microorganisms that help regulate coagulation, other medications can cause it to rise, taking a double dose of warfarin accidentally, liver disease, poisons, and other things can cause an INR to climb.

Perhaps I should have said 'don't trust the lab reports' or something else -- to me, saying 'labs' begins from the time they put the needle in my arm, to the time a result is sent to the doctor.

(In the case of the results mentioned at the beginning of this thread, another person whose blood was drawn for an INR on the same day that mine was, had a reported INR of 7.1. According to the lab, they tested my sample twice, and probably did the same with the other person. SOMETHING clearly went wrong -- was it a bad reagent at the lab? Was it a wrong tube or mishandling samples at the doctor's office? Was there a problem with the tubes used? I'm not in a position to ask any more questions. But, the point I wanted to make is that results CAN, and sometimes do, get messed up by the 'professionals' whose job it is to draw the blood, appropriately handle it, and accurately analyze it. We can't have blind faith that results are always accurate).

 

[carolinemc]

The manual says it reads 0.8 to 8.0, but later on it says for measuring range to check your paperwork with the strips.

There is a paper from 2007:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1860570/

There are no data points above an INR of 4 (Figure 1) but who would let their INR get above 4 just to see if a meter is correct

Also don't blame the labs, maybe the problem was with the blood draw, the container/preservative or the handling of the sample before it got to the lab.

There was a recall on those strips for that were not any good for INR reading. They were recalled for two years. And I never blamed the labs for I always had good ranges and knew when I took something different, it changed the INR readings. Antibiotics and eating a salad(not a regular salad eater), would wreck my numbers. Luckily never went to 4. I would have had a heart attack(just kidding).

 

[Protimenow]

Carolinemc - the CoaguChek XS strips were recalled because readings were not accurate - the readings were higher than actual INR. I'm not sure about the two year recall - I assume that this meant the recall was for the batches of strips, and included blocking them during the time that they were not expired.

As far as my post about not trusting labs, I stand behind it. I noted that one lab gave an INR of 5.2. When I found out about it, I had my blood tested by two other labs - 3.6 and 3.5, and did testing on two of my Coag-Sense meters - 2.8 and 3.0. CLEARLY, THE FIRST LAB GOT IT WRONG.

This wasn't the first time I got wacky readings -- the hospital reported a 6.6 in November - I didn't get home to test my INR, and the hospital didn't repeat the test.

A clinic a few years ago got a 7.1 -- my INR on the meters was in range. The clinic GOT IT WRONG.

More than a decade ago, before I started self-testing, a doctor's office told me that my INR was 7.1. It probably wasn't.

The lab that reported 5.2 last week, also reported 7.1 for another patient whose diet and dosing were stable.

I have a friend who is a former lab tech, and he also noted that labs DO sometimes get things wrong.

I realize that diet, antibiotics and other factors can change INR -- but these don't negate the fact that LABS CAN GET IT WRONG.
I know of one clinic that will repeat any lab tests where INR is 4 and above (and they use Coag-Sense to do this), and I know that the clinic last week that got a 5.2 apparently repeated the test. This suggests that the blood was mishandled between the doctor's office and the lab, or the lab's reagent was wrong, or that the lab tech didn't perform the test correctly, or maybe the tubes used to hold the blood weren't made properly, or who knows what?

Labs are not perfect. They sometimes make errors. Sometimes it makes more sense to blame the labs, rather than blaming your meters.

 

[pellicle]

Could you point me in the direction of some of those documents?

sorry, I missed this earlier.

https://www.hpra.ie/docs/default-source/field-safety-notices/august-2018/v36870_fsn.pdf?sfvrsn=2

I know that some strips were recalled last year because of potential inaccuracy over 4.5, but I was not aware that there is a wider and general concern about accuracy of the CoaguChek XS above 3.5

that's what the document says,

which then somehow morphed into this:

http://www.clpmag.com/2019/02/fda-warns-unauthorized-sales-home-use-warfarin-test-strips/

FDA has recently issued a warning to patients and doctors who use at-home or in-office medical devices to monitor levels of the blood thinner warfarin that certain test strips used with the devices may provide inaccurate results and should not be relied upon to adjust the drug dosage.​

... but I guess public panic being what it is lets all rush into hysteria right?

 

[pellicle]

Carolinemc - the CoaguChek XS strips were recalled because readings were not accurate - the readings were higher than actual INR.

not strictly true

so "inaccuracies" were between 1.5 and 4.5 ... however the issue is really that the labs were not complying with the new WHO standards.

 

[Protimenow]

I was actually referring to older studies that indicated errors in CoaguChek XS and InRatio strips when INR exceeded 3.5 (if I recall).

I'm glad to learn about the recalibration by Roche. I'm also interested to see that some labs haven't complied with the new WhO standards.

When I can afford to, I'll get some of the new batch of CoaguChek XS strips and compare the results to the Coag-Sense and a trusted lab or two. It'll probably be a while, though, until I can get some XS strips.

I'd like to recalibrate my comparison between meters, if the XS strips more closely match the labs. (Of course, I don't plan to let my INR rise above 3.5, but I can still get a sense of whether the XS agrees with the labs, and how close to the Coag-Sense values it reports.

 

[carolinemc]

I was actually referring to older studies that indicated errors in CoaguChek XS and InRatio strips when INR exceeded 3.5 (if I recall).

I'm glad to learn about the recalibration by Roche. I'm also interested to see that some labs haven't complied with the new WhO standards.

When I can afford to, I'll get some of the new batch of CoaguChek XS strips and compare the results to the Coag-Sense and a trusted lab or two. It'll probably be a while, though, until I can get some XS strips.

I'd like to recalibrate my comparison between meters, if the XS strips more closely match the labs. (Of course, I don't plan to let my INR rise above 3.5, but I can still get a sense of whether the XS agrees with the labs, and how close to the Coag-Sense values it reports.

I once went to the lab(at the hospital) and it had the reading of 4.0. We had it rechecked a week later, 2.3. We made the slight change on dosage and went back to normal dosage after the normal reading. And it was antibotic that did the rise. I always make sure the checker knows when I am on any different med, since we keep me at the lab and the cong check is done right there.

 

[Chris]

Carolinemc -- leafy greens should lower your INR, while the others may raise it.

Protimenow, when you say that "while others may raise it", are you saying that physical activity will raise someone's INR? I see you mention antibiotics, specifically, as something that will raise an INR reading, but I was wondering about exercise.

thanks,
Chris

 

[Protimenow]

Carolinemc - I don't think that exercise will change your INR. Antibiotics and some OTC supplements and herbs can affect the INR. I know that antibiotics CAN change the INR (I'm not sure which direction the change will be), and it's always a good idea, when making changes to your medications or supplements, or even when your warfarin is manufactured by another company, to test your blood to make sure that any changes are detected.

My pharmacy changed my generic warfarin from one company to another a few years ago. I wasn't able to effectively control my INR. When they made the change, I tested a few days later, and watched the INR fluctuate as a result of this new source. I insisted that they change it back to my trusted manufacturer and have had no problems since then.

 

[carolinemc]

@Protimenow, I have had several experiences with increased exercise and raised INR. It has happened several times since 2001. When you are not consistant in exercise and suddenly increase activity, it will raise the INR. I would be asked if I was taking any other meds or taking antibotics. Ask you doctor and you will something new. Consistancy is important.

 

[Protimenow]

So, by your reasoning, if you increase the amount of exercise, your INR will go up. Conversely, if you decrease the amount of exercise, your INR will go back down?

Me doctor ('ask you doctor') wouldn't have a clue. I can only learn that he knows little about INR. And, as far as I'm concerned - consistency IS important. (I'm assuming that you left out the word 'learn' when you said 'ask you doctor and you will something new' - Right?)

Increased activity, which will necessarily cause you to eat and drink more (and different?) foods, may have an effect on INR. Similarly, if your exercise suppresses the work of the digestive system in metabolizing warfarin (just as antibiotics kill gut bacteria that also have an impact on how warfarin is broken down in the body) may have some effect. I personally haven't noticed any difference in my INR regardless of amount of exercise.

Has anyone else reading this thread had experience with INR increases as a result of increased activity or INR decreases when activity is reduced?

I don't have time right now to explore whether there's a linear relationship between increasing activity and increasing INR.

 

[Agian]

Nope. No effect. When I get my fat arse into gear, I see no change in INR.