Coag-Chek meter information wanted

[pellicle]

I can't imagine a .8 difference being acceptable in all cases. If a test result was 2.3, does this mean that an actual INR of 1.5 is acceptable? I believe that the acceptable standard is +/- 30%. This is what most meters can do - in my experience CoaguChek XS had a higher degree of variance at high INRs - and I believe this has been well documented.

well firstly I guess that it makes a difference if that 0.8 difference is from an absolute or both are variance around another number which is somehow the "true" INR.

We know well that INR is a rubbery indicator at best and INR is dependent on the reagents used ... indeed its not even a number that we know affords any specific case by case "protection" against clots.

For what its worth my own testings have never been greater than 0.3 on any lab vs my coagucheck I've ever done (and I've done a few)
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(*Note: this is not time series data, but each point is just a date where I made a sample ... somehow I've lost some of the sample points of comparison with the lab ... don't know why)

What matters is not what individuals report, its what you find for yourself with your gear.

I always encourage people to do baseline checks not just once, but perhaps once per year ... and if variance is found request information on reagents.

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There are known blood disorders (which are uncommon but exist) which can influence the INR readings.

Discuss with your doctor and if in doubt just compile some data and look at your own situation

 

[Protimenow]

I've found that the lab's reagents can make a significant difference in reported INR. I have probably fifty or more comparisons between meters and labs, and may produce a series like the one that Pellicle posted, when I kick myself into gear and create one.

On the subject of reagents - INR is calculated by dividing the prothrombin time (the time it takes to form a clot) by a value that is specific to the reagent (reagent in the strip, or reagent at the lab). For at least a year, my Coag-Sense was giving an INR value that was usually .1 or .2 below that reported by the lab. I asked the meter's manufacturer about the difference (although I was completely satisfied by the reliability of the difference - always .1 or .2 off), I thought I'd get a response. The manufacturer's response was that the lab was probably using a different reagent.

I had a test at the lab last week - after going six months without bothering to make a comparison with the lab. The results were almost exactly the same - INR values matched, and prothrombin times were within .4 seconds of each other. I haven't confirmed that this match will happen again, but it strongly suggests that the lab has changed to a different reagent whose value matches the one in my strips. Producing a reagent value takes a bit of accurate guesswork - there's no solid standard for creating an 'exact' reagent value.

When I get a chance, I'll see about putting together a lab versus meter comparison chart.