A DIFFERENT Meter - Coagusense

[pellicle]

Hi

I didn't understand any of that.

Basically the same way your washing dries, evaporation.

In this case its selective evaporation. I remove the alcohol, not the water or (many) of the other compounds.

 

[Protimenow]

You probably don't want to waste the alcohol - although there's probably not a whole lot to waste -- but distill will give you a less alcoholized wine (you can't really remove ALL the alcohol from the wine), and, potentially, an interesting Brandy.

 

[marc_kowal]

Just curious if you have tried this with any other beverages besides wine?

 

[Protimenow]

Middle of the range is absolutely the place to be. And your point about not trusting the meter to give 'absolute' figures is extremely important. I used to trust my old InRatio to be CORRECT - and it turned out that a 2.5 was actually more like a 1.8. As much as you think that your meter and strips are accurate (after all, they wouldn't be allowed to sell these if they weren't, would they?), there is always the reasonable probability that your meter and a lab's values won't match.

(I was told by a person who should know that CoaguChek XS and Coag-Sense usually report very close to each other, and these results are also close matches to the labs).

What has been troubling me about the Coag-Sense versus CoaguChek and InRatio was the LARGE difference between the Coag-Sense and the others. A 3.2 on the Coag-Sense (nicely in range, thank you) is reported as way above 4.0 by the other meters.

So -- my advice is to learn your meter by running a number of comparisons to a lab that you trust. If there's a regular amount of variance, you should be able to figure out an adjustment to your meter's values; if the lab and your meter match closely, so much the better.

My adventures with other meters - Coag-Sense, CoaguChek XS (and, when they were supported, the CoaguChek S), InRatio and InRatio 2, and ProTime Classic and ProTime 3 - were all part of my quest to find the most accurate meter. I had a TIA a little over a year ago, in part because I trusted a meter that told me that my INR was higher than it actually was -- and I don't want to create a situation where this can ever happen again. It's part of my goal to determine if there really IS a most accurate meter (based on only one or two of each type), and reporting these findings.

 

[Protimenow]

I've been doing so much testing recently that my test day (for once weekly testing) has moved from Friday to Monday. Using the 'thread around the finger' trick, I was able to get a great flow of blood -- I put a big drop on the CoaguChek XS strip, and was able to get ample blood for the Coag-Sense a few seconds later. Both samples were applied within fifteen seconds of incising my finger.

The results didn't match my historical expectations:

CoaguChek XS: 2.8
Coag-Sense: 2.5

Both meters tell me that I'm in range, if perhaps near the bottom, but I'm not concerned. This is by far the biggest drop that I've put onto an XS strip. I wonder if the XS meter will pass Quality Control and provide a result even if it doesn't get enough blood on the strip. I'll test again - with a BIG drop on the XS - next Monday. I'm wondering if there's an 'error range' where the meter doesn't really get enough blood, and delivers an inaccurate result, but still passes quality control. Again -- I'll have a better idea about this next week.

(I have a lot of InRatio strips -- maybe I'll use one with a BIG drop and see what it reports)

 

[pellicle]

I wonder if the XS meter will pass Quality Control and provide a result even if it doesn't get enough blood on the strip.

my experience on this is that you don't need a big drop, but you do need to get enough to fill the capillary cavity of the test strip. I can often get away with a smaller drop by applying it to the edge of the stip. If however its not enough to deliver it (and I'm getting a feel for the minimum size now) then it will error and that's that.

 

[Protimenow]

That's been my experience, too. I have only gotten the error once -- I usually put what seems like an 'adequate' drop on the left side of the strip, and the capillary action draws the blood in. I'm just trying to see why, for probably the first time, the results of the Coag-Sense and the CoaguChek XS are so close. (I'm not complaining, but curious, because I don't think that this has happened before).

 

[pellicle]

I'm just trying to see why, for probably the first time, the results of the Coag-Sense and the CoaguChek XS are so close.

ahh ... I'd interpreted this as you presenting them as another example of variance. I know you know intimately what you have published before but I had not commited to memory the variances between them to know if you were saying: it was a big gap OR it was a narrow gap.

 

[Protimenow]

OK

A few examples:

6/17/13:
Coag-Sense: 3.3
InRatio 2: 4.7
CoaguChek XS: 4.2

5/31/13:
Coag-Sense 3.5
InRatio 2 5.2
CoaguChek XS 4.8

---

I have seen differences of 1.0 or more, pretty consistently.

Having very close (2.5 vs 2.8) results was a pleasant surprise.

 

[pellicle]

I was simply meaning that you could add those extra 4 words to the post and it would have been clearer. My philosophy on writing is to use as little as possible to convey my idea to someone who doesn't have my assumptions.



The variances seem high, but then you are in a high INR range.

lastly the inRatio2 and XS are within 0.5 and 0.4 which seems acceptable to me ... while the the CoagSence when compared to the XS (to which it is closer) is 0.9 and 1.3 respectively. This indicates that the percentage error of the Coagsence is getting greater as INR raises.

the standard deviation between each sample set is 0.7 and 0.88 (which includes your Coag-Sence the most deviant)

of course all this is just waffle without a reference to a known standard.

If I was forced to interpret such data I would personally choose to take the middle of the range as the most likely and that happens to be the XS

IF you had included reference to a blood draw for each of the data sets (not the day before, or the day after) then this would be very useful data, as it is it is just pub conversation on which will be the winner.

 

[Protimenow]

Yes, I actually DO need a blood draw from a lab that I can trust.

I had two blood draws during the time that I had the Coag-Sense (it's sense, not sence -- unless that's the Australian way of spelling the word). I didn't get the CoaguChek XS until after my last blood draw.

Here are the results of the blood draws and tests on the meters -- same day, usually within an hour or two of each other:

3/1/13

Coag-Sense 2.5
InRatio 2 testing error - no result
Lab 2.7


3/28/13:
Coag-Sense 2.3
InRatio 2 3.0
Lab 2.7


Since that time, as you've observed, as the INR gets higher (on any of the meters), the difference between the Coag-Sense and the CoaguChek XS and InRatio 2 results widen. It's been documented that the results on some meters (the CoaguChek XS and the InRatio) skew increasingly above labs when the INRs get higher. Thus, a 4.0 on a CoaguChek XS or InRatio 2 could possibly actually get a 3.2 or so in a test at a lab. As the reported INRs on these meters increase, so does the amount that the meter over-reports.

For INRs of 4.0 and above, some labs REQUIRE a blood draw. I was told by a person at Coagusense that some clinics test with the Coag-Sense when the other meters report 4 and above.

FWIW - I have a lot of InRatio strips, and decided to do a test today (the day after my tests with the Coag-Sense and CoaguChek XS, so not really comparable), and got a 2.8. I suspect that the lower the INR actually is, the closer the results of all three meters will be.

I'm inclined to conclude that even though the CoaguChek XS and InRatio show very similar results on all tests, this isn't conclusive evidence that they are accurate. They could be biased in the same way when the actual INR increases. Without actual evidence either way (until I get a blood draw), I'm personally inclined to trust the Coag-Sense a bit more than the other meters because of the method it uses to determine Prothrombin Time and INR.

I'll know more once I've actually HAD a blood draw.

 

[pellicle]

I had two blood draws during the time that I had the Coag-Sense (it's sense, not sence -- unless that's the Australian way of spelling the word).

no that's just my poor sense of spelling ... I could blame other things, but in the end its just me.

I'll know more once I've actually HAD a blood draw.

look forward to it

thanks for all your fine work

 

[Protimenow]

You're welcome. Thinking back a few months to the time that I started this thread, it is clear that my goal was (and is) to find the most accurate meter - and to communicate my experience with each meter. I don't want anyone to give blind trust in a particular meter's accuracy (like I did) and have them pay for it later.

That's one of the reasons that this idiot wound up with meters using four different technologies (ProTime, InRatio, CoaguChek XS and Coag-Sense), and that I'm still in pursuit of a meter that isn't even available for mere mortals (because the Hemochron Junior requires frequent quality control testing and is supposed to only be available in medical facilities).

The fact that I encountered some widely divergent test results - especially at hgher INRs - was something that interested and somewhat confused me. I realized that being in range was my most comforting state of being - but in range on one meter was significantly above range on two others.

I may actually GET a blood draw tomorrow (maybe) and, if so, I'll punish my little digits in order to compare the meters to the lab.

One of my long term goals is to see that anybody who is taking Warfarin can get tested regularly - at home, or at testing centers - regardless of ability to pay. A secondary goal - with which I've been active in this thread - is to assess the relative accuracy of the various meters. Unfortunately, the last goal is mostly anecdotal, based on my own specific experience and blood chemistry. Perhaps widening it at some time in the future - and possibly adding testers who are lucky enough to have more than one meter - can help to make this a bit more representative of the actual state of things.

 

[Protimenow]

I just found some interesting documents relating to INR testing. The one here: http://www.quickmedical.com/downloads/coagusense_inr_system_white_paper.pdf is apparently sponsored by Coag-Sense, but includes some quite interesting points relating to reliability of testing methods, variance between testing methods (I've even seen some interesting reports on variances based on different lab procedures, and one report that said that blood drawn at a lab should be tested within four hours of the blood draw -- in my experience, many clinics hold the blood for daily pickup by the lab, so the results are, almost by definition, inaccurate and unreliable).

At the bottom of this document: http://www3.hscni.net/stlabs/webhb/poct/documents/coaguchek training manual.pdf, there's also an interesting paper regarding the CoaguChek XS and overall testing accuracy. This paper is interesting because it goes into a fair amount of detail about HOW the CoaguChek XS determines INR and seems to be more detailed than much of what I've seen previously.

I MIGHT get a blood draw today - I'm not sure. If so, I'll quickly follow this test with testing on my meters. If so, I'll report on these findings in a few days, once I get the results from the blood draw.

 

[pellicle]

Nice one pro time the manual PDF had some interesting bits.

I think you have made a mistake in your analysis of the treatment of blood samples. I am confirming with a pathologist mate and will comment later.

 

[pellicle]

Protime, with respect to blood handling procedures for INR I found the following


In Australian hospitals the follow is not atypical

Test within 2 hours of drawing the sample. If it will be longer than two hours, centrifuge the tube (3000 rpm), pull the plasma off into a second tube, centrifuge that tube, pull the plasma off (except for the bottom 0.5 mL or so) into another tube. Freeze. Transport frozen.

Reid Hospital in the US (picked at random) has this:

The specimen should be transported to the laboratory as soon as possible and centrifuged within one hour. If it is not possible to transport the specimen to the lab within one hour the specimen should be centrifuged at 8500 rpm for 180 seconds or 3000 rpm for 10 minutes. Tubes should remain capped until the test is performed. Patient plasma should be tested within 24 hours if stored at room temperature, or within two weeks at -20° C and within six months if stored at -70° C..

So with basic handling protocols it seems that there is no rush.

 

[Protimenow]

I'm referring to a protocol that I saw that said that the blood should be centrifuged, and that the plasma should be tested within four hours. This is often not the way that it's done.

I assume that most hospital labs are equipped to test the INR fairly promptly. I'm referring, instead, to the clinics and private doctor offices where the blood is drawn, spun in a centrifuge, then held for hours until it's picked up by a lab courier. I've seen these tubes put into styrofoam containers and left locked in a box on the door of the doctor/clinic office until a courier picks up the blood, moves onto the next office, and finally puts them in his/her car. Eventually, the blood actually gets to a lab. I had an experience with one such clinic, which I suspect didn't handle the blood particularly well, and it came back with a result that didn't seem consistent with my meters or a hospital lab.

I was able to get a BLOOD DRAW today. I should have results on Friday.

My results two hours after the blood draw are these:

Coag-Sense: 2.2
CoaguChek XS: 2.7
InRatio 2: 3.0
Coag-Sense: 2.1

The reason that I tested twice using the Coag-Sense was that I was still a bit surprised by the .5 variance with the XS and the .8 variance from the InRatio, especially with a reported INR being so low. I was putting the first drop from the first incision directly onto the XS strip and drawing up the blood that was still on my finger immediately after making the incision, and putting that onto the Coag-Sense strip. All of this was still 'first drop' and within fifteen seconds, but I wanted to be sure that my technique wasn't causing the Coag-Sense to be lower than it should. The second test with the Coag-Sense was made with the blood on my finger immediately after the incision, and with the mini-pipette (instead of a transfer tube) used for getting the blood off the fingertip and onto the strip. The test with the InRatio 2 used a new incision and a different finger. I may test with the ProTime 3 a little later (the strip has to warm up, and more blood is required), because I don't want to waste the lab result by NOT testing with this meter.

Once I get the results of the blood draw, you can probably count on me disclosing it -- and perhaps jumping to some conclusions (or not).

One other thing -- I heard from a nurse at the Anticoagulation Clinic that the NEW protocol for aortic valve replacement specifies an INR of 2.0 - 3.0. Having had a TIA at what I thought was higher than 2.0, and allowing for the permissible +/- .5 INR for the meters, I would NOT be willing to take the risk of a 2.0 on some of my meters. (A 2.0 on my InRatio 2 will cause me to confirm with another meter and probably to increase my dose right away -- I had a TIA when an InRatio reported more than 2.0 and the risk of error is one risk that I am UNWILLING to take). I feel much safer when I'm within +/- .5 of 3.0.

 

[pellicle]

Hi

I was able to get a BLOOD DRAW today. I should have results on Friday.

will be interesting to apply to this data set

My results two hours after the blood draw are these:

Coag-Sense: 2.2
CoaguChek XS: 2.7
InRatio 2: 3.0
Coag-Sense: 2.1

The reason that I tested twice using the Coag-Sense was that I was still a bit surprised by the .5 variance with the XS and the .8 variance from the InRatio, especially with a reported INR being so low.

well its interesting that you put all these together, as then if we take the average reading as 2.5 and work out the variance its not as bad as that. Statistical variance works out to be 0.18 and the max and min values from the average are +0.5 -0.4

Which isn't too bad all things being equal. It will be interesting to see where the blood draw comes into it with this.

Once I get the results of the blood draw, you can probably count on me disclosing it -- and perhaps jumping to some conclusions (or not).

look forward to it as always

One other thing -- I heard from a nurse at the Anticoagulation Clinic that the NEW protocol for aortic valve replacement specifies an INR of 2.0 - 3.0.

personally I'd see that as a target of 2.5 ... and I understand your preference to be above than below that number Nothing wrong with a target of 2.7 if you ask me.

 

[Protimenow]

Few of us have the luxury of testing with multiple meters, so the idea of an average is nice -- but impractical. As long as each of us has a meter that we can trust - and we know what is ACTUAL minimum on that meter (for example, on an InRatio, a 2.5 on the meter actually equates to a 2.0 in a lab), we should be able to stay out of danger of stroke or TIA and, if we know an upper limit, we can also avoid hemorraghic problems.

I will be testing with my Protime 3 in a few minutes (7 hours and one glass of wine after the blood draw), so I can see how this compares to the other meters and the lab.

 

[pellicle]

Few of us have the luxury of testing with multiple meters, so the idea of an average is nice -- but impractical.

I raised average in my discussion as your figures have no baseline, so an average of them is the only meaningful way to discuss variance between the readings.