False Increases in INRs - QC doesn't catch - WARNING

[Protimenow]

I've been using INR meters for three years. I had assumed that changes in my INR relating to medications, food, etc., were actual changes in my INR. For example, when I had to take antibiotics, I realized that my INR would go up (and it did), and that the reports from my meter were accurate. I had assumed that if I changed my diet - adding or removing greens, for example, that my INR actually changed. I had, thus, trusted my meter to accurately reflect my actual INR, and I adjusted my dosing for these changes that I assumed to be real and correct.

Two weeks ago, I had stroke, although my INR was reported by my meter to be 2.6.

I'm aware that lab tests and results from a meter don't often match. I've also relied on quality controls built into the meters and the strips to detect error conditions.

So - when my INR a couple days ago was reported as 3.8 by TWO meters, I was pretty comfortable that my INR WAS close to 2.8. I was surprised this morning when I learned that an INR from a blood draw just 90 minutes after my tests using my meters was 3.09 -- .71 points lower than the results on my meters. I was inclined to suspect lab error or mishandling of my blood by the lab -- until I spoke to Alere.

Alere's advice: trust the lab. They noted that labs spin the tube that contains the blood, separating the plasma from the blood cells, and separating medications from the blood cells. The lab tests strip out confounding factors that meters can't.

A lightbulb went off in my head when I was reminded of this. An OTC that I was taking -- supposedly a good antioxidant -- called Quercetin had fooled the meter into reporting a higher INR than my ACTUAL INR. I had assumed that it just made my INR higher (as other medications sometimes do), and adjusted my dosage of Warfarin so that I would stay in range. In effect, by reducing my Warfarin dose to accommodate to the .8 spike caused by this medication, I was reducing my ACTUAL INR to dangerous levels.

I'm stopping QUERCETIN beginning immediately. Even though I can probably adjust for a 3.3-4.3 INR, and account for the effects of the Quercetin, it's just not worth the risk.

So -- a few things to be learned from this:

There are OTC and other medications that can fool the meters into reporting higher (and perhaps lower?) INRs than your actual INR. Modifying your dosage based on these false highs (or lows) can be disastrous. (I was blessed enough to find this out without major injury).

If you make changes in your medications (other than antibiotics and pain relievers whose actual effect on INR is already well documented) and see changes in the INR reported by your meter (especially changes more than .3 or .4), get an INR based on a blood draw to confirm that the reported change is REAL, and not just a substance fooling the meter.

IF you encounter a material that you suspect causes such an erroneous spike in INR reported by your meter, let us know. The more we all know to avoid, the better off we'll be.

 

[sarahsunshine]

This is great information to have. Do you have alits of what these 'ingredients' that cause 'false' increases in INR are? Quersetin, I assume, is a brand name. What is the ingredient that causes the false increase?

 

[Eva]

Too bad this happened to you and a bit scary

I test twice a year through my doctor's lab right after testing on my machine. The results are almost the same!

Could a device or strips have anything to do with this inaccuracy?! Where one buys them from?! Etc. etc.

 

[Protimenow]

Quercetin is a generic name, not a brand name. I've seen it available from many suppliers. It's available with and without extra Vitamin C.

I wish there WAS a list of such medications -- if I could, I would like to develop such a list. I didn't realize that you could get a false elevation in INRs WITHOUT an actual change in INR. Quercetin, from my own experience, should probably be avoided (although, in theory, if you were able to figure out how many points it will make an INR spike, you could theoretically still take it and adjust based on this error).

I am usually very confident in the results reported by my meter. Two years ago, when I was testing with the ProTime meter, I had a 2.9. The next day, I got a concussion, and the hospital lab got a 2.92. I trusted my ProTime meter to be accurate, and to remain accurate.

When I got my InRatio meter, I compared the results of both meters, and they were almost the same. I trusted the InRatio to be within limits, and certainly accurate enough to keep my INR in range.

The methods that the meters use to detect changes in prothrombin times may be sensitive to things besides actual clotting. In the case of Quercetin, it apparently make it look TO THE METER as if it's taking longer to clot than it actually does. I don't know if this same phenomenon occurs in the other meters -- or if there are certain substances that effect tests by other meters differently and a list of medications that can fool the meters should be compiled for each machine.

In answer to Eva's question -- I believe that the problem was one with the InRatio meter. It's not necessarily an InRatio problem - this is something that Quercetin somehow slightly disrupts the way that the InRatio detects clotting. I don't think it has anything to do with a particular lot of strips - I think I've seen the same error with two different lots.

Not having a CoaguChek XS or current cuvettes (strips) for my ProTime meter, I don't know if I would get a different INR - or error message - from these other meters.

My goal is not to condemn any meters from any manufacturer but, rather, to call attention to the possibilities that SOME medications COULD cause falsely elevated readings on certain meters and to be aware of these medications. Also - if you have a doctor who can prescribe it, and the funds to cover it, it doesn't hurt to have occasional blood draws to confirm the accuracy of your meter.

 

[njean]

This is precisely 'why' I don't take any supplements and/or OTC medications without first consulting my doctor. There are too many things out there, i.e., supplements, teas, remedies, etc., that can conflict with anticoagulants and pose potential danger if not caught in time.

In my humble opinion, I would caution anyone who is recommended a certain supplement, remedy, whatever, to check with their doctor FIRST!!!!

 

[Protimenow]

Jean:

The problem with asking a doctor is that, in my limited experience, few doctors actually KNOW about these things - and they certainly can't be expected to know about idiosyncracies of certain meters. Quercetin was recommended in a book by a doctor, but without any specific warnings.

I suspect that we probably have access to information about drug interactions, etc., that doctors have access to. Even if the Physicians Desk Reference (PDR) lists a particular OTC as safe, it probably won't list it as one that alters INRs reported by specific meters.

Rather than the meter makers saying 'talk to your doctor,' it would be good if the meter manufacturers maintain lists of OTC and prescription 'medications' that may (or do) cause the meters to give erroneous results. This information could be made readily available to physicians -- and should also be available to anyone interested in determining the compatibility of a material with a meter. (If, in retrospect, I could have gone to the Alere site before starting to use Quercetin, typed the name of the stuff into a 'no-no' database, and learned of its effect on tests made with the meter, I may have been properly anticoagulated because I wouldn't have taken quercetin in the first place. Rather than asking a doctor - who probably wouldn't have an answer - I could have found out and made an educated decision about whether or not to use the stuff. Such a list of known issues, maintained by each meter's manufacturer, would be a good first step at preventing others from having similar problems).

 

[sarahsunshine]

I agree to check with the doctor first, but I also caution that most doctors simply say "don't take it" because they have no trust in homeopathic and other remedies that aren't in the mainstream western medical stream. There does have to be a happy medium... comparing tests with the clinic seems to be the only way, currently, and to truly investigate when there is a discrepancy.

Fortunately our clinic test come out within .1 or our Coacgucheck consitently, and the other Coaguchek consistently is off by .2 (taken at the same time with the same venous blood - we get the clinic to put a drop on the strips for us at the same time they take it for the test). We know what to expect. But if they are inconsistently off, or vary by more than .4 or .5, then a full on investigation would be in store.

 

[Protimenow]

One strategy that may work is, if adding anything to your regimen, do it one item at a time, and test after a few days. This way, it's likely that you'll be able to detect changes in your INR and know which thing is the likely culprit. If ANY of the things you add results in a spike in the INR, it's time to either discontinue whatever you added, or to get the INR confirmed by a blood draw. Given my recent experience with Quercetin and InRatio, it's not appropriate to ASSUME that a particular addition to your diet/medications has actually spiked your INR or just merely fooled the meter. (Of course, it's also good to do some research on the medication and see if there are already contraindications reported for it).

 

[Bill B]

There is no good way to know whether adding or removing another drug or some food is causing a real effect on INR or a false one unless you do confirmatory lab draws every time you do this.

This is an important warning that the meter manufacturers should make clear upfront. It appears you had a stroke at least partially because they did not inform you that you could have falsely high INR readings from certain drugs. Is that true?

How is your recovery from the stroke going?

 

[Protimenow]

Bill: I've been assuming that changes in INR reported by my meter were actual changes, and not artifacts introduced by materials that confound the meters. I suspect that rapid changes may be more a result of error than actual change (except in the case of things that actually DO change INR -- antibiotics, some pain relievers, sources of Vitamin K). I adjusted my dosage based on an inaccurately high reported INR.

There may be many substances out there that produce the same artificial spikes (or drops) in reported INRs as the one that I encountered. Manufacturers, understandably, don't want to advertise that their meters can ever be inaccurate or report false results - but it DOES happen, and the people who use these meters SHOULD BE MADE AWARE of the changes and of what to avoid. Just saying to avoid everything is not a warning that many will fully respect. I've been preaching for a long time - as have others - that high INRs reported by meters should be confirmed by blood draws. In my case, with a 2.6, I wouldn't have gone for a confirming lab test. It's important that people be made aware of the possibility, not that a particular material will make INR increase or decrease, but that some materials can result in ERRONEOUS INR values on certain meters.

As far as my stroke goes, it WAS confirmed by MRI. It WAS a stroke (not just 'appearing' like a stroke). It was an ischemic stroke - the result of a clot getting lodged in the brain. Fortunately, it was relatively minor and, aside from supposedly avoiding stress, I expect a full physical recovery. However, I'm feeling energized about taking action to prevent this kind of event happening to others.

 

[AgilityDog]

PT, remember, you can have a stroke even if your INR is in range. Clots can be blood clots or fatty clots, or vegetative clots, etc. I wouldn't be so quick to blame the meter.

 

[Protimenow]

Laurie:

I'm not placing blame on the meter -- but if there are issues where a material can fool the meter into reporting a higher than actual INR, this should be pointed out. If there's blame to be handed out, certainly a good portion would fall directly onto myself for not shooting for an INR that was nearer the top of my range, or for being unable to get a new batch of strips and testing weekly. (Yeah, I know that there are some out there who are comfortable with monthly testing. I once was. I'm not anymore).

The point is that if there WERE materials that cause meters - from whichever manufacturer - to report erroneous values, there should be good knowledge about these products. The more we all know about any confounding medications- and how they influence meter accuracy - the more able we'll be to effectively manage anticoagulation.

 

[tom in MO]

I just had my valve put in, and every single medical person (surgincal nurse, cardio-nurse, pharmacist, cardiologist, cardio-PA, surgical-PA) that I saw in the hospital and afterward stress one big caution. Do not take any drugs, herbal supplements, vitamins, minerals, etc. w/o consulting your warfarin dosing team. If a doctor prescribes a new drug, don't take it w/o consulting your team. It's the one big rule they all stressed. Did you consult your team before taking Quercetin?

 

[Protimenow]

Team? Team?

That's the best laugh I've had all morning.

 

[tom in MO]

Why do you find it funny? In the hospital, numerous people came to talk to me and train me in warfarin. I had a pharmacist, a nurse, a video, a surgical PA, a cardologist PA and a nutritionist all discuss warfarin with me. The hospital takes a "team" approach. Afterwards, in rehab, the dietician, nurse and recreational specialist have all discussed my warfarin, my diet and my exercise with me and they have access to my INR results. When I saw my cardiologist, he knew my INR history and discussed it with me. Same with my surgeon. I use a coumadin clinic. They sound like a team. They can't always answer my questions, but call back with what the "doctor" said. Their approach is to dose the diet not diet the dose, with two caveats. First, I must tell them if I get ill or change my eating and exercise habits. Second, I must tell them of all new drugs, perscription, over the counter, herbal, etc. that I begin taking, before I take them. Their dosing regimen monitors what others on this board do. If it acts like a team, quacks like a team

 

[Protimenow]

I find it funny because, for years, I've gone without ANY medical professionals, other than the one who was able to renew my prescription for warfarin.

There's nothing wrong with having a team -- but we CAN'T ALL HAVE A MEDICAL TEAM THAT SUPPORTS US.

I've been on my own - no insurance coverage, not enough money for medical attention, for many years.

I've only recently - after my stroke - been able to get some medical support, but before this, the 'team' was me and my wife and NO MEDICAL PROFESSIONALS because we couldn't afford medical professionals.

I'm not disputing the fact that you've got a team behind you -- just questioning the assumption that, because YOU have a team, EVERYBODY does.

 

[Bina]

This is precisely 'why' I don't take any supplements and/or OTC medications without first consulting my doctor. There are too many things out there, i.e., supplements, teas, remedies, etc., that can conflict with anticoagulants and pose potential danger if not caught in time.

In my humble opinion, I would caution anyone who is recommended a certain supplement, remedy, whatever, to check with their doctor FIRST!!!!

Yeah, what she said....NJean has been on Coumadin for 37 years without any problems, she knows of what she speaks.

 

[yotphix]

Hi Protime. First, I'm very sorry to hear that you had the stroke, but very pleased to hear that you seem to have come through it relatively unscathed. I have a question for you regarding the Quercetin. You may know that it's a relatively common substance, and that it occurs in many things we regularly ingest. This from Wikipedia:

"Quercetin is a flavonoid widely distributed in nature. The name has been used since 1857, and is derived from quercetum (oak forest), after Quercus.[2][3] It is a naturally-occurring polar auxin transport inhibitor.[4]
Foods rich in quercetin include black and green tea (Camellia sinensis; 2000–2500 mg/kg), capers (1800 mg/kg),[5] lovage (1700 mg/kg), apples (440 mg/kg), onion, especially red onion (191 mg/kg) (higher concentrations of quercetin occur in the outermost rings[6]), red grapes, citrus fruit, tomato, broccoli and other leafy green vegetables, and a number of berries, including raspberry, bog whortleberry (158 mg/kg, fresh weight), lingonberry (cultivated 74 mg/kg, wild 146 mg/kg), cranberry (cultivated 83 mg/kg, wild 121 mg/kg), chokeberry (89 mg/kg), sweet rowan (85 mg/kg), rowanberry (63 mg/kg), sea buckthorn berry (62 mg/kg), crowberry (cultivated 53 mg/kg, wild 56 mg/kg),[7] and the fruit of the prickly pear cactus. A recent study found that organically grown tomatoes had 79% more quercetin than "conventionally grown".[8]
A study[9] by the University of Queensland, Australia has also indicated the presence of quercetin in varieties of honey, including honey derived from eucalyptus and tea tree flowers.[10]"

Do you know offhand what the dose was that you were taking? Having looked at this list I now wonder if the very occasional mysterious spike in INR I have experienced might well have resulted from too much green tea, apples, red grapes, or combinations of such things. So far, I've only had a few such spikes take me out of range, and so far I haven't adjusted my dose for them since I felt that I was still within 'safe' range, if not my prescribed range. With the knowledge of what happened to you, I'm glad of that, and I will certainly take it into consideration in future such cases.

Thanks for sharing this info, and working to sort out what may have happened. Speedy recovery to you.

Paul

 

[karla]

What an enormously helpful thread though it's a shame that a stroke started it all. Glad you are doing well.
As a relative "newbie" to Warfarin ( 2 months now), I had already decided to forego any supplements, etc since very few, if any, studies have been done describing possible interactions. I think that's probably why docs ( and anyone else for that matter) aren't going to be able to say with certaintly that a particular suppolemetn, herb, etc is OK to take with warfarin - unless studies have been done that they can point to that says it's OK.
Reading everything here has confirmed to me that my decision was correct. Thanks, all.

 

[Protimenow]

Thanks for the information on Quercetin. I was/am taking Natrol Quercetin+C - one tablet daily. This gives me 250 mg or Quercetin plus 700 mg Vitamin C.

I've started and stopped it a couple times - and the INR seems to spike about .6 or .7 when it's in my system (as reported by the InRatio machine). I had assumed that my INR actually rose because of the Quercetin. Lab tests dispute this. I don't have ProTime strips, or a CoaguChek XS to see if these meters report a similar INR, but I'll be getting tested at a lab that uses a Hemochron, which uses a method to determine prothrombin time that is different from the one used by InRatio. I've continued to take Quercetin, in large part, so that I can see with the Hemochron reports.

(If I had the money to get more ProTime strips, I'd run tests on my ProTime to determine the value reported by that meter. There's another, new, meter that I'm hoping I can get so that I can confirm on it. If/once I get the new meter, I'll report my experiences with it).

Yes, fortunately, my stroke was small, and in an area where I'm able to recover pretty fully. I'm feeling as if my recovery is complete - but I'm not entirely pleased with a blood pressure medication that I was given. On the whole, I feel like I've been blessed.

Plus - if there REALLY IS an issue with Quercetin - or any material - causing results that spike on certain meters compared to blood tests, it's certainly important for this information to given out -- especially if labs use a particular machine that exhibits this bias.