CoaguChek xs vrs the lab... someone is wrong!

[Guest]

So I plunked down the $550 bucks for a CoaguChek xs machine from the pharmacist. Today is my Inr test day at the lab, so I run my first test at home, come up 2.4 nice, I go to the lab fifteen minutes later and they phone me back and its 2.0 and jack up my warfarin again. CRAP I said so I ran another home test... 2.4 WHAT THE HELL!

Any one else buy a bum machine or is my lab rolling the dice in the back room coming up with numbers?

Paul

 

[Paul]

Ooops I was so miffed I forgot to log in before I posted ... guest is me..Paul

 

[pellicle]

Hi

well at least you know that your INR testing using your machine is consistent test to test.

To answer your question, firstly there is no way to be sure that the lab has followed all the standards in calibration and reagent choice (reagents are the chemicals that are used to trigger thrombosis from your blood sample and measure its time to "clotted")

A for instance (from Roche)
[IMG2=JSON]{"data-align":"none","data-size":"full","src":"https:\/\/c2.staticflickr.com\/6\/5784\/21878002284_075c4a55ce_b.jpg"}[/IMG2]

So as you see nothing in measuring INR is that "accurate" (accurate = using a steel calibrated caliper to measure a block of steel at ISO standard temperatures), there are always squiggles. So if there was a plus or minus 0.2 difference between "reality" (lets assume for a minute such exists) and the measurements from the lab were -0.2 and your Coagucheck was +0.2 then both would reflect what is "true" within their tolerances.

Next, lets look at this graph, which shows the deviations between one lab experiment and an XS

[IMG2=JSON]{"data-align":"none","data-size":"full","src":"https:\/\/c2.staticflickr.com\/4\/3759\/12770827565_a44c6cc77f_b.jpg"}[/IMG2]

and

[IMG2=JSON]{"data-align":"none","data-size":"full","src":"https:\/\/c2.staticflickr.com\/8\/7426\/13290360903_cfed9501cf_o.jpg"}[/IMG2]

To read that lower graph, take any point and move horizontally across to obtain the XS reading from that point (which represents a particular blood sample under study), and then read vertically down to obtain the Lab INR obtained by that.

So you can see that there exists a such a "cloud" of uncertainty which becomes larger as INR raises (and as it happens matters less as INR goes higher). This is explained by differing blood chemistries (as this was some hundreds of blood samples).

So basically if you have one thermometer you think you know the temperature, if you have two you'll always see a small difference. For what its worth most labs will tell you that 0.2 INR is of no clinical significance. So if your reading was 2.4 and then 2.6 (for instance) an INR manager would make no change.

Myself as long as you've followed all the Roche procedures (not strongly milking the finger, not waiting longer than 15 seconds between lance and blood drop application ...) I'd tend to stick with the Coagucheck reading

SO ... now you know why I think the INR = 1.7 lower limit that On-X touts is dangerous ... depending on "reality" you may be 1.4 or less ...

Hope this helps

Best Wishes

PS, this website seems to reduce or enlarge the image, so especially with the first larger image, right click it and open it in a new tab ... so you can read it better

 

[Paul]

Thanks for the information it was very informative.
I was expecting a difference of at least 0.2 not 0.4. The thing that bugs me is I was 2.0 last test so they increased my dosage to 7mg 5 times a week and 6 mg twice and the result was the same.... seems kind of weird you would thing it would go up slightly not stay the same. So now we are doing 7mg every day and will test again at the lab ten days from now. I will compare the results again.


Paul

 

[Agian]

FWIW, I'm running my INR a bit higher. So if my machine shows 2.8 and the lab 2.4... meh.

 

[lance]

Hello Guest,
rest assured XS is not a "bum" machine. I'd pay more attention to the dose response to the difference in test results. Chances are for a .4 difference the change in dose would be the same. It would be helpful if we knew your prescribed range. Over time, 18 years on warfarin, 15 years self testing firstly with Coaguchek S and when it wore out Coaguchek XS. Prior to self testing I experienced 3 TIA's because of mismanagement. Over this time comparison tests (lab vs XS) the difference has been .2-.3 difference. Recently spouse and I took comparison lab tests at the same time. My lab result was .1 different from my XS. Spouses was XS 3.2, lab 4.0.. So what happened there? We'll never know and if not for POC home testing. Incorrect lab test was sent to PCP who made a totally incorrect dose adjustment.
So trust your XS. In time you will come to this conclusion too.
Best wishes--happy testing and your non-scarred vein will thank you.

 

[ForeverThankful]

Just for the record, my CoaguChek XS readings are always a bit higher than lab readings, usually 0.2 to 0.4 higher.

 

[Agian]

Prior to self testing I experienced 3 TIA's because of mismanagement.

Yikes! What happened? If you don't mind me asking.

 

[Warrick]

FWIW I did a side by side test last week with my XS and the hospital lab (first time ever) , they use the XS plus, I was pleasantly surprised that both readings were INR 2.3 bang on

Other times I've done both tests on the same day and had around 0.2-0.4 difference from memory. As it's nicely pointed out above different methods produce different results.

Love might not be the right word but I love my meter and the minute or so we spend together once a week...

 

[lance]

Agian,
Yikes indeed.
PCP's office thought the correct range for me was 2-3 probably because I was the first patient with a mechanical mitral valve. When lab results were usually lower and I was being told they were fine I accepted it. After the third TIA I insisted I should be 2.5 to 3.5. I was very vocal. Then I heard about Point Of Care self testing. SO out of bad came very good on several fronts. I learned to manage INR, I learned about POC testing and the scarring of my vein for INR testing ended. I was/still am a member of a clinical trial investigating the accuracy and efficacy of POC testing being held by a major Toronto hospital. Along the way I learned enough about INR management that my PCP advised my spouse I could manage his INR because of A-fib. Everything has gone well for many years.b No TIA's for him.
Prior to my PCP's retirement he admitted it was his fault the TIA's occurred. So case closed and I was very lucky.

 

[lance]

FWIW I did a side by side test last week with my XS and the hospital lab (first time ever) , they use the XS plus, I was pleasantly surprised that both readings were INR 2.3 bang on

Other times I've done both tests on the same day and had around 0.2-0.4 difference from memory. As it's nicely pointed out above different methods produce different results.

Love might not be the right word but I love my meter and the minute or so we spend together once a week...

Ha ha. The minute spent with XS so much better than travelling to the lab and waiting, waiting for the test result.. Right on.

 

[pellicle]

Lance

The story about your TIA is just so familiar to me, it fits the mold of arrogance and a blinkered vision of "how it should be done" (usually how it was done) that I have seen so many times (and experienced a little myself too). It's a failure to accept that newer may be better + a loss of control in making the patient the one in control. Very much against the traditional power hierarchy that exists in medicine. Not all are like that, but a many are, and most show a tincture of it from time to time.

PoC is change for the better for any who are not intellectually feeble , who are capable of cooking for themselves and don't need their meal served and their chin wiped with their napkin.

Ha ha. The minute spent with XS so much better than travelling to the lab and waiting, waiting for the test result.. Right on.

This part of the bonus to PoC is just gravy isnt it.

When they inserted the cannula into my elbow for my recent PET scan the clinician commented that I "had good veins" and I thought well you can thank self testing for that. Your point is one overlooked by many, that is the accumulative effect of that weekly small cut to your vein.

 

[Agian]

Prior to my PCP's retirement he admitted it was his fault the TIA's occurred. So case closed and I was very lucky.

That was very noble of him.

Thanks for the heads up matey! Knowledge is power and you've just added to mine.
Despite having an on-x I've decided to keep my inr above 2.5.
Glad everything worked out for you.

 

[kolyur]

I'll add to the consensus here that you shouldn't be worrying at this point. When I started with my XS a year ago my numbers were all over the place and it was really stressing me out. Like you, I thought I had a defective machine. Once I got a consistent testing procedure in place, however, the results got a lot more steady and believable. See my thread here:
http://www.valvereplacement.org/for...85-inr-level-via-lab-draw-vs-fingerstick-test

The biggest thing for me was getting the blood onto the test strip quickly. They say 15 seconds but I think less time equals more accuracy. On a good day I can now do about 5 seconds between finger prick and machine beep. I was also getting lots of error 5's (not enough blood = wasted strip = frustration) until I realized that I can flex the strip a bit with the pricked finger and it helps work the blood into it. Having the proper lancing tool helps too.

My routine now is to check weekly with the XS and go in once a month for a lab draw. I do an XS test on the same day as the lab test so I can compare results. My home results are almost always in the range of 0.1-0.3 higher than the lab number, and I'm satisfied with that variance. Maybe it's overkill to do it both ways but the lab is only 5 minutes from my house and I like comparing the numbers. Not to mention I sleep better at night.

 

[lance]

That was very noble of him.

Thanks for the heads up matey! Knowledge is power and you've just added to mine.
Despite having an on-x I've decided to keep my inr above 2.5.
Glad everything worked out for you.

I bear responsibility for that too because I didn't make myself heard. Not so any more.
I think keeping your INR above 2.5 is probably a good idea.

 

[pellicle]

I bear responsibility for that too because I didn't make myself heard. Not so any more.

Bravo!
I hope more people read this point and live it.

 

[lance]

Agian
nothing to ad.

 

[dick0236]

I think keeping your INR above 2.5 is probably a good idea.

Me too! Blood cells are easy to replace, but not so with brain cells.

 

[Paul]

Did the home test.... 2.6 got the results back from the lab..2.4 that's a little better.

I do one more test before leaving Jamaica on the 27th.

So far so good.

 

[Protimenow]

The POCs have changed over the years. I started self-testing in 2009, when I was able to get a ProTime meter. It was big, kind of clunky, had a bit of a learning curve, and the strips required refrigeration. But it worked.
When I got an inRatio, it was smaller, strips didn't require refrigeration, and seemed to be my meter of choice...but I made one error -- I relied on its accuracy. I tested every week or two, consistently getting readings of 2.4 -- but I had a TIA. The INR in the hospital lab was 1.7 -- later, it was 1.8 - I had gone for weeks with an INR that was too low, even though the meter said 2.4 (I got a 2.4 before I went into the hospital). The InRatio has been removed from the market - a few years too late, based on my experience.

After getting out of the hospital, I was convinced that I should try other meters, and went on a quest to find the most accurate meter - my life, and the life of other self-testers, relied on it. I got a Coaguchek-S (the XS hadn't come out yet, or was just too expensive), and, later, an XS. I tested on the Protime, the InRatio, the S or XS, then the hospital lab or a clinic lab.

When I got my Coag-Sense, I added this to the mix. For many months, I compared meter results to each other, and to a blood draw.

In some cases, I found the results of the XS and the InRatio to be much higher than the blood draw -- in some cases more than a full point or more too high. The Coag-Sense stayed closer to the labs. And not all labs were to be trusted - nor were the doctors or practitioners who prescribed the dosing based on the INR results.

My personal choice came down to the CoaguChek XS and the Coag-Sense. It seemed, on many occasions, that the lab results fell roughly between those of the XS and Coag-Sense. The Coag-Sense was often .1 or .1 below the lab. The XS was often as much as .3 above the lab value. All were within acceptable limits.

For myself, I decided on the meter that reported a value equal to or lower than the lab value. This way, I would be sure that a 2.0 on the meter wasn't LOWER than a 2.0 at the lab. By contrast, a 2.0 on an XS would have me wondering if my lab results would be 1.8 or so. Because I'm not as concerned with a slightly high INR than I am about one that is too low, I chose the Coag-Sense. Although it's less well known, isn't backed by a massive marketing team, is larger than the XS, and isn't quite as easy to use, it's my personal preference.

Whichever meter you use, get some blood draws (as others here also do), so you can learn (possibly) how your results vary from the lab results. Armed with this knowledge, you should be able to self test (and maybe self-dose) and be confident that your INR is in a safer range.