A DIFFERENT Meter - Coagusense

[Protimenow]

It's beginning to get a bit confusing. The most important thing, I guess, is that if my range should be 2.0-3.0, I'm in range. I'm comfortable with 2.0 - 3.5 -- as long as the 2.0 isn't actually 1.7 or so.

On Wednesday, I had a lot of bleeding after cutting myself shaving. This was unusual for me -- I tested my INR on the CoaguChek XS - and it was 3.1.

Today - Saturday early A.M., I did my usual Friday test a bit late. The Coag-Sense gave me a 2.4. Supposedly, the Coag-Sense uses a method that matches the one used by labs. I tested with the CoaguChek XS a few minutes later and got a 3.0. The variance was a bit surprising - but not atypical for my comparisons between the two meters.

Not willing just to take the two readings and accept one as possibly correct, I also tested with my InRatio 2. This time, I used a Unistik 3 lancet and got a good drop of blood on the strip. (In the past, my drops may have been barely adequate for an accurate test). The InRatio also gave me a 3.0. The actual prothrombin times for the Coag-Sense meter (29.5 seconds) and the InRatio 2 (29 seconds) are almost identical -- reagents may make a difference.

What sort of surprises me is the agreement between the CoaguChek XS and the InRatio 2 -- the last two tests, they were identical. The first time that I compared the two meters, they were within .1 of each other. I am somewhat surprised by the large difference between the Coag-Sense and the other two meters.

If I can find a willing finger, I may run a test with the Protime 3 later today, just to see how it compares to the other three meters (a 14 hour lag between tests shouldn't change INR all THAT much).

If I had coverage, I'd get a blood draw and see how it compares to the other meters.

(After wasting two CoaguChek XS strips on Wednesday, and, in the past, wasting strips for other machines because I didn't have a large enough drop of blood, I'm now using the Unistik 3 Extra lancing device. Spending a quarter or so for the lancing device, versus almost nothing for a 21 gauge lancet, makes sense when you consider the cost of strips wasted because of inadequate blood supply).

(I'm also tempted to run quality control tests on the Coag-Sense, just to be sure that it's accurate)

Any suggestions or comments are. of course, invited.

 

[chaconne]

Based on your unique position of having all these meters and comparing to them to eachother and lab draws, it seems to me that INR measurement is not as precise as we hoped it was. My guess is that the standard deviation in measurements is about 0.5. This is what I've seen with my InRatio2. Most my readings are near 3.0, but I get an occasional 2.5, and even more rare, a 3.8. If this is true, it seems that shooting for the middle of our INR range is the way to go.

 

[pellicle]

Based on your unique position of having all these meters and comparing to them to eachother and lab draws, it seems to me that INR measurement is not as precise as we hoped it was.

Well the testing is very very approximate and would not be accepted for results even at an undergraduate degree level. The results are interesting but caution needs to be used in interpreting them.

- there was no baseline blood draw per test to compare with
- there are but a few samples
- it is confined to one person (so individual variation in blood chemistry is ignored)

The information is valuable in that it serves to remind that measurement of INR:
- is not an precise science (have you ever compared blood draws across multiple labs?),
- that some variations are to be expected,
- that you should not attempt to shave your levels close to the limits of your range (and so stay in the middle of your range)
- INR measurement is not like taking a micrometer to a piece of steel and measuring its thickness.

When taken this way we can see that with the variance recorded by the meter is sufficient to allow us to stay "in range" more of the time than (say) monthly lab draws.

Again I take my hat off to protimenow and say thanks for publishing this information, however it needs to be interpreted within the context that it is provided.

 

[Protimenow]

I was testing against blood draws. A few months ago, I had blood drawn at two different labs on the same day (and also tested with one or more meters - I don't have the INR file open), but there was a significant difference between the two labs -- a difference that really concerned me.

True - I was testing with just my own blood. The tests were all done within minutes of each other.

The tests reflect interaction with my personal blood chemistry.

I'm hoping that it isn't the case, but some INR measuring technologies may be insensitive to hematocrit issues, while others aren't. It is possible but I hope not probable that there may be something in my blood chemistry that makes a meter measure high (or low), and doesn't give an accurate INR result. I suspected more than a year ago that Quercetin made the InRatio measure higher than actual.

True - INR is not an accurate thing. Results can differ from lab to lab. The same blood with the same meter and the same lot of strips can yield slightly different results. As has been suggested (and as I've also suggested), it's probably most sensible to shoot for the middle of the range, with any meter(s), and to occasionally try to correlate to a blood draw from a (possibly) more accurate lab.

 

[pellicle]

Hi

...and doesn't give an accurate INR result.

its important to keep in mind that the issue of concern is that of clot formation. We use INR as a guide, but as I understand it : it is an indicator of likelihood not an absolute measurement / prediction of clot formation

True - INR is not an accurate thing. Results can differ from lab to lab.

which means that no matter what is supplying the data you can expect variance. Which is why I suggested caution in using these things for absolute figures.

The same blood with the same meter and the same lot of strips can yield slightly different results.

supporting why I urge being more in the middle of your range than trying to skim the edges, thus meaning that all these measurements are quite sufficient.

And having somone like you to make such a comparison as this is only a good thing. It gives some level of reassurance that things do indeed act as advertised / expected.

 

[Protimenow]

The primary issue is one of clot formation. That's the reason for the minimum values being above 2 (or, to be safe, above 2.5 or so). In my case, I trusted my meter, which was giving me 2.0, and in the Hospital, the INR was 1.7. Although I was told by a cardiologist in training that the desired INR for an Aortic Valve patient is 2.0-3.0 (and I questioned him on this, because of the possibility of error at both ends), I am personally much more comfortable when my meter tells me 2.5 or higher.

There's another concern - the issue of being OVER anticoagulated. INRs above 4 or so put us as somewhat greater risk of hemorrhage (spontaneous bleeding, internal bleeding, bloody urine, etc.)

I will be testing again on Friday, probably using the Protime meter, testing against the CoaguChek XS and maybe the Coag-Sense. Values that are consistently .5 or more under the CoaguChek XS may make me wonder about other factors in my blood -- not a good thought, but there ARE some things that may cause the meters to skew the results.

If my meters (or a lab) tell me that my INR is somewhere between 2.5 and 3.5, I'll feel confident that I'm in range.

 

[chaconne]

True - INR is not an accurate thing. Results can differ from lab to lab. The same blood with the same meter and the same lot of strips can yield slightly different results.

In my limited experience (about 20 tests with an InRatio2, two of which were compared to a lab), testing several times in one day (4 times) gave nearly the same results (3.2-3.3) and the labs agreed pretty close to the InRatio (0.2, 0.1). You both (Pellicle and Protimenow are people after my own heart). I love this part of having a mechanical valve and look forward to more testing and an improving understanding of how it all works. Thanks for your posts.

 

[Protimenow]

I"m not entirely sure that ANYONE really understands how it all works.

I'm hoping that having a mechanical valve has changed your life a lot for the better. I'm sure that this is the reason that all of us walking around with a prosthetic (mechanical or tissue) valve had the surgery.

My goal in all this testing (and in the possession of 7 (believe it or not -- but I don't, and can't test with all of them) meters) is primarily to determine, if possible, the meter that most closely matches the labs (if the labs can even be trusted for accuracy), and ultimately to help people who may otherwise be unable to get their blood tested and INRs managed. I think that I'm doing fairly well with the self-testing part. It would be a great public health event if all the people on anticoagulants could get their INRs tested weekly - whether or not they can afford the tests.

The fact that I'm exposing some significant differences from meter to meter (and the surprising agreement of a few different meters) seems rather interesting to me. In my own case, the differences between Coag-Sense and both InRatio 2 and CoaguChek XS may reveal some blood issues that one meter ignores and the others are equally effected by. I don't know.

My ongoing goal - aside from the public health thing that I mentioned earlier - is to be sure that my INR is above the bottom of the range ON ANY METER.

I'm glad to see that you're doing your own testing. I'm glad to see that you're making some comparisons to the lab. Your INRs probably WILL change slightly at different times of day while your dose of warfarin from a few days ago and your level of anticoagulant in your system drops.

 

[pellicle]

When this infection clears up I am intending to do some travelling. Having a compact light weight device to take with me is something that makes me feel Unchained.

 

[Protimenow]

And you'll feel less chained with your XS than you would with the other meters. I like the size and the convenient strip and lancing device storage of the XS. It's also good to know that, should your batteries give out during an extensive trip, they can easily be replaced by standard batteries. (The InRatio 2 is also pretty compact, but I think that the XS slightly edges out the InRatio 2).

 

[Protimenow]

It's been more than a month since anything was last posted on this thread. I got the Coag-Sense meter because, on paper, it seemed to be potentially the most accurate meter available -- it uses a spinning wheel and an optical sensor. When a clot forms, the wheel stops spinning, and the meter delivers exact prothrombin time and calculates the INR. This sounds simple.
I haven't been able to get a blood draw - lab test in a few months, so I can't compare the accuracy of this - or any other - meters to a blood test that is assumed to be the most accurate measurement of prothrombin time and INR.

When compared to results reported by the other meters, the Coag-Sense always seems to report a lower INR.

Results from tests today show this:
Coag-Sense: INR: 3.3, PTT: 39.6
InRatio 2: INR: 4.7, PTT: 46.9
(the above two tests were taken within minutes or each other)
CoaguChek XS INR: 4.2 (This was taken 7 hours later).

It's been well documented that the InRatio and CoaguChek XS can report higher than actual values when the INR gets above 3.5 or 4.0.

I'm remain concerned about the variance from the Coag-Sense and the other meters. I was told that the CoaguChek XS and Coag-Sense results are usually very close to each other.

Pellicle will probably chide me for not getting a blood test to confirm my actual INR. In order to do this, I'll have to find a lab and get a prescription for this simple test.


(On another point -- although there have been discussions every few months about whether or not wine can change the INR, it appears that with one wine, at least, in my body, the answer is YES. When I have more than 8 ounces, or so, of a particular Pink Moscato wine, my INR increases up to 1.5 points over where it probably would be otherwise. The increase according to the Coag-Sense isn't nearly as high as it is on the other meters, but it IS an increase, and has put me out of range a few times (according to the InRatio 2 and CoaguChek XS). Wine, for me, DOES seem to raise my INR. This, of course, should be part of another thread, but I wanted to toss it in here as an item of interest)

 

[pellicle]

Hi

It's been more than a month since anything was last posted on this thread.

and I have been sort of curious to know how things were going ...

Results from tests today show this:
Coag-Sense: INR: 3.3, PTT: 39.6
InRatio 2: INR: 4.7, PTT: 46.9
(the above two tests were taken within minutes or each other)
CoaguChek XS INR: 4.2 (This was taken 7 hours later).

which is an average of 4 ... and puts the Coaguchek sortof in the middle

Pellicle will probably chide me for not getting a blood test to confirm my actual INR. In order to do this, I'll have to find a lab and get a prescription for this simple test.

well I'm sort of more interested in the 'test with a mate' compare you were going to do

.. or did I miss that?

Wine, for me, DOES seem to raise my INR. This, of course, should be part of another thread, but I wanted to toss it in here as an item of interest)

not bad to know ... goes with my red wine and aspirin approach to any SHTF scenarios ...

I have been dealcoholising (to around 3%) my red wine lately, so will be interested in what effect that's had on my INR when I test this weekend (yes, you can assume my consumption of red has gone up)

 

[Protimenow]

I haven't checked against my friend's meter and strips -- but really SHOULD in the next day or two.

The wine that I'm referring to is a Pink Moscato -- I don't think that the issue is alcohol - there are other things in the red wine that may affect INR.

OTOH -- the spike in the INR reported by the XS may be spurious, or an increased response to something in my blood(?) that it's not adjusting for (or something). The reason that I say this is that I gave up on the idea of having a 'new, unused' Coag-Sense meter, and figured that I can probably sell or trade it even if it was used for one test.

The results of the tests with the TWO Coag-Sense meters, separated by about 7 hours, were almost the same - 3.3 in the first meter and 3.2 in the second. I won't guess why the minor difference -- it could even be a rounding error. The nearly identical result from the two meters increases my confidence in the Coag-Sense meters.

The INR spike, in relation to the Pink Moscato, doesn't seem to occur with the Coag-Sense, but I AM seeing the spike in InRatio and CoaguChek XS. I wonder if there's something left over by the wine that has the effect of messing up the impedance measurements used by the XS and InRatio.

I'll report on my parallel XS testing once I do the tests.

 

[pellicle]

Hi

The wine that I'm referring to is a Pink Moscato -- I don't think that the issue is alcohol - there are other things in the red wine that may affect INR.

that's what I was thinking. Since I'm dealcoholising my wine (leaving the other stuff) and my consumption has gone up (due to the reduction of alcohol being a limit) I'll be interested to see if my INR is altered (and I use a coaguchek)

will report on Sat

 

[Protimenow]

I look forward to seeing your results.

In regards to my XS -- I'm wondering if there is a problem - I was told by Coag-Sense that the results from a Coag-Sense usually track pretty closely to those of the XS. I'm thinking that, because my meter was used, and my strips were gray market (bought on eBay from a seller who is located in Roche's city but doesn't seem to specialize in items like anticoagulation testing), one or the other or both may be producing the inaccuracy. And, if there IS a problem with either the meter or the strips - and the issue really can't be detected unless validated with a blood test (or Coag-Sense, perhaps), how will home testers with similarly suspect test hardware/supplies even KNOW that there IS an error?

I'll report more once I've had a chance to test against a friend's XS (he's a doctor, so I am quite confident that both his meter and strips are accurate).

 

[Protimenow]

I'm making this a second post, rather than a response to Pellicle.

There doesn't seem to be much about the Coag-Sense that is particularly error prone. The strip has a small wheel that turns when the strip has been properly heated. A small bar code on the underside of the strip is read by the meter, and contains the values for the thrombin (and probably expiration date and other details). When blood is added to the strip, an optical sensor watches the wheel spin - once the clot forms, an actual prothrombin time is detected. The meter takes that time, does the calculations based on the thrombin value that was attached to an code area on the strip, and the INR is calculated. This is a physical determination of PTT and INR. Intuitively, it seems as if this may be the most accurate test device, even if it's not as easy to use as the CoaguChek XS or InRatio.

It seems that the main point of error is in the coding data on the strip -- although I'm sure that the manufacturer is extremely careful in making sure that this value is accurate.

Until yesterday, I still had some concerns about the accuracy of the Coag-Sense, in light of the high degree of variance from the CoaguChek XS and the InRatio meters. A parallel test with a SECOND Coag-Sense put those concerns to rest. A 3.3 in the morning using one meter, and a 3.2 seven hours later on the second meter are strongly suggestive, to me, that the method works. (It's possible that both machines are subject to the same error factors, but I think that they both achieve the same high degree of accuracy).

If I find that my XS - or my strips - or both - are producing inaccurate results, I may just use the Coag-Sense for testing. They've just released a new 'transfer tube' that makes it even easier to get and transfer the blood, and this will probably become my meter of choice. OTOH - if I get the sense that the Coag-Sense is NOT accurrate, I'll still wait around scratching my head about which is the most accurate.

I'll let you know what I find out, once I test my XS against my friend's.

 

[pellicle]

Since I'm dealcoholising my wine (leaving the other stuff) and my consumption has gone up (due to the reduction of alcohol being a limit) I'll be interested to see if my INR is altered (and I use a coaguchek)

will report on Sat

INR was 2.7 (last week was 2.8) my dose remains constant. So I can infer that 1/2 a bottle of dealcoholised red per night is having no significant effect.

 

[Agian]

How are you removing the alcohol from the wine? Does it taste OK?

 

[pellicle]

Hi

How are you removing the alcohol from the wine? Does it taste OK?

At this stage it is by heating to 78 ~ 82 deg C and then chilling to minimise the time at higher temps. I was concerned that this may be too rough on temperature labile components, but wanted to "suck it and see". My next stage will be by vacuum distillation.

As it happens the dry reds gas off the alcohol quite swiftly in a shallow wide dish heated on a gas stove. White wines seem harder to remove the alcohol. Perhaps the sugars bind the alcohol in solution tighter and raise the vapor point. Suites me as I drink reds

Taste is (to my tastes) mainly altered by the lack of alcohol rather than by any "cooking effect" that may occur. My neighbours and friends are all of the view that as the second glass with a meal you wouldn't notice.

A side effect seems to be that cheap wines seem less sharp than before the process.

 

[Agian]

I didn't understand any of that. Sounds like fun but.