CoaguChek error 8

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leadville

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Thought i would share my experience today with my Clinic

I self test once per week.

My machine for a while has been showing error 8 , a restart usually sorts it out
Today i was given a replacement machine at my Doctors.

My machine showed INR 2.6
New machine 2.8
Doctor's calibrated machine 3.0

I was advised that UK best practice allows a 0.5 variation in the machines, if i were to have a Lab venous draw they allow 15%

the test were done within minutes of each other using 3 different finger draws


I was surprised at the tolerances allowed but at least i have learned something.
 

pellicle

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Hi

interesting story ...

leadville;n884482 said:
My machine for a while has been showing error 8 , a restart usually sorts it out
Today i was given a replacement machine at my Doctors.

My machine showed INR 2.6
New machine 2.8
Doctor's calibrated machine 3.0
For those reading here are the manual mentions of error message 8 (well and 9 for good measure)



I agree with the views of errors margins allowed in the UK and is the reason I strongly advocate target INR not "oh I'm within my range" when your range may be 2 ~ 3 and you're on 2 ... exactly stuff like this is why you don't want to sit on the margins.

To me its like Tennis, return to the middle of the court as soon as practicable.

Some other information you may find helpful is:

There is an important concept called "clinically significant" in interpreting readings. So a INR variance of 0.2 is not clinically significant, thus 0.4 would be on the margins but no action would normally be taken. Thus 2.6 vs 2.8 is not a clinically significant variance. Perhaps (taking an analytical approach it is wrong to assume that the 3.0 is actually bang on (and indeed this is always a rubbery measurement anyway) in which case we could equally assume 2.6 to be correct and the obtained readings are within +- 0.2

Its always going to be the case that there are minor differences between batches and between measurement systems. Even "blood draws" depending on reagent and lab compliance with "baseline" setting will yeild differences. This is an interesting section from a Roche Publication:


In testing we see that the errors become smaller as INR decreases as in this test publication:


None the less its a good topic to bring up as while its been discussed here many times, not everyone digs through the archives.

Best Wishes
 

leadville

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pellicle;n884484 said:
I agree with the views of errors margins allowed in the UK and is the reason I strongly advocate target INR not "oh I'm within my range" when your range may be 2 ~ 3 and you're on 2 ... exactly stuff like this is why you don't want to sit on the margins.
Hi Pell , i have never thought about it that way but it makes perfect sense

Thanks for the extra info, it's very useful to know this stuff
 

Dodger Fan

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Every time I get a blood draw, I also use my Coaguchek. The blood draw is usually .2 to .3 lower than my meter. I decided a while back to report .3 lower than what the meter says because I know that if I report a 2.0, I am in reality a 1.7 and they won't change my dose (range is 2.0 to 3.0). I could make my own dosing decisions, but I prefer to let them do it for me. I have been self testing since March of 2016.
 

Protimenow

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Dodger Fan -- In a more recent thread, I asked why you would report a lower than meter value to your INR manager. I'm assuming that they don't already know that these meters report .2 to .3 higher than the labs. Your reasoning for reporting lower results sort of makes sense, as long as the manager doesn't also do this. So - if the meter says 2.0, and you tell your manager it's 1.7, and the manager concludes that it's actually 1.4 - their decision may be a bit more extreme than expected.

FWIW - I use the Coag-Sense, which often reports slightly lower than the labs for a similar reason to your logic. For me, I'd prefer a meter that reports slightly low - if my meter gives me a 2.0, I'm fairly comfortable in the belief that a lab result would be 2.3 or so, and put me at the low end of my range. A 2.0 on a CoaguChek XS would concern me.
 

LondonAndy

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I decided a while back to report .3 lower than what the meter says because I know that if I report a 2.0, I am in reality a 1.7 and they won't change my dose (range is 2.0 to 3.0).
I self-test weekly, and adjust my own dose when needed. I give the result to my anticoagulation clinic every 6 to 8 weeks, which is whenever they ask for it, and I always give them the exact same figure as shown on the meter. This is because if ever I have something serious happen and need to go into hospital, I think trust in my self-management would be lost if they found different readings to those I have provided. This may be an unlikely situation, but as I ended up with a pacemaker that will need replacing every 7 to 10 years or so perhaps there will be occasion for a comparison to be needed.
 

Protimenow

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If the hospitals weren't making so much money on the labs, I wouldn't be surprised if they used a meter, too -- and charged $50 to read the result and another $50 or so to analyze it.
 

pellicle

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If the hospitals weren't making so much money on the labs, I wouldn't be surprised if they used a meter, too -- and charged $50 to read the result and another $50 or so to analyze it.
in australia they often do use a Coagucheck ... in fact its where I was first exposed to the idea (back in the ward after ICU after my 2011 OHS).

Of course being Australia I'm not charged $50 for that ...
 

Protimenow

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Yes. Enlightened medical systems do things like that for their people.

I saw my first INR meter - a Protime - in 2006. I finally was able to get one in 2009, when I started self-testing. (It was a person's grandmother's meter, and he made me a gift of it. I had a doctor friend order the strips. I've been self-testing for more than a decade).
 

tom in MO

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In the US, Medicare covers home testing as do private insurance policies. It's cheaper to home test than deal with the expenses of being out of range.
 

Protimenow

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I can see expenses when you're out of range (below range - long enough, you can have a stroke) (you'll probably know you're above range because of excessive bruising or, perhaps, even blood in the urine). Strokes are expensive - and could be life ending; excessive bleeding is easier to control with Vitamin K -- probably not as expensive.

It's definitely cheaper to home test than it is to deal with the below range consequences.

I may have to see what Medicare will do for me - although I already have meters.
 

tom in MO

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I can see expenses when you're out of range (below range - long enough, you can have a stroke) (you'll probably know you're above range because of excessive bruising or, perhaps, even blood in the urine). Strokes are expensive - and could be life ending; excessive bleeding is easier to control with Vitamin K -- probably not as expensive.

It's definitely cheaper to home test than it is to deal with the below range consequences.

I may have to see what Medicare will do for me - although I already have meters.
From Wiki: Medicare coverage for home testing of INR has been expanded in order to allow more people access to home testing of INR in the US. The release on 19 March 2008 said, "[t]he Centers for Medicare & Medicaid Services (CMS) expanded Medicare coverage for home blood testing of prothrombin time (PT) International Normalized Ratio (INR) to include beneficiaries who are using the drug warfarin, an anticoagulant (blood thinner) medication, for chronic atrial fibrillation or venous thromboembolism." In addition, "[t]hose Medicare beneficiaries and their physicians managing conditions related to chronic atrial fibrillation or venous thromboembolism will benefit greatly through the use of the home test."
 

Superman

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I’ve always wondered about timing and the impact. I believe you need to provide a sample within 15 seconds of the finger stick.

So if you get there in 3 seconds vs 15 seconds, wouldn’t your test result vary? Taking three tests that close together, did you get your sample to the machine in the exact same amount of time? Or is that an insignificant impact on outcomes?

It appears the manufacturer believes waiting longer than 15 seconds from the stick would have enough of a material impact to make the result useless.
 

Protimenow

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The reasoning here, as I understand it, is that the blood will start to clot within fifteen seconds, throwing the value off.

I'm not sure about what happens between the time of incision, and the time fifteen seconds after incision.

It could be that any change in clotting activity between second 0 and second 15 would affect the detected INR by less than 20% of the result.

It's possible that with either meter - CoaguChek XS or Coag-Sense, a person should be able to have the incision and sample ready to go at or near second 0, incising the finger right as soon as the warming timer hits 0. (I may be wrong, but the Coag-Sense DOES have a countdown timer).

With the CoaguChek XS, it should be easy to test at second 0 if you put your finger near the strip just before incising it. I can't see it taking fifteen seconds to incise the finger, then touch the drop to the strip.

This question shouldn't be too hard to answer - just use two strips and two fingers - waiting to place the drop for one of the tests.

The clotting mechanism may not be linear - clotting may accelerate more, the longer blood has been mixed with the reagent - so the first few (15, perhaps) seconds may not be involved in much of the clotting -- it's that last seconds when clotting activity accelerates.
 

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