CoaguChek error 8

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leadville

Premium Level User
Joined
Aug 28, 2017
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175
Location
Wigan, England
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.
 
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pellicle

Professional Dingbat
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Nov 4, 2012
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6,057
Location
Queensland, OzTrayLeeYa
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

Premium Level User
Joined
Aug 28, 2017
Messages
175
Location
Wigan, England
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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Joined
May 6, 2015
Messages
92
Location
Temecula, CA , USA
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.
 

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