More GAS -- another meter

[lance]

With all due respect my fingers are fine from my weekly testing with one meter and are not a cause of concern.
Most users are not compulsive obsessive and do not require multiple monitors to assure themselves of their accuracy.:wink2:
XS is highly accurate and has been for many years.:thumbup:
It's best to not muddy the waters for newbies who might find management a challenge that hasn't been mastered yet.
So far you are the only user criticizing monitors. Most, if not all, users wouldn't be without theirs.
AND
The slight differences mentioned wouldn't change a dose response anyway.:smile2:

 

[Protimenow]

With all due respect -- I had an InRatio and, like most others, believed that it was accurate. Without overstating it, you could say that I trusted my life to its accuracy. I trusted that a 2.6 on the meter kept me in range -- and then I had what the doctors called a stroke. In the hospital, the first day that they tested my INR, it was 2.7. The next day, it was 1.8. I left the hospital with Lovenox -- and a concern that, like me, others also trusted their meters, and that NOT ALL METERS DESERVE SUCH BLIND FAITH.

I didn't want what happened to me to happen to others.

I embarked on a quest to help me determine how the meters compare both to each other and to the labs. Call it OCD if you really must, but my goal was to find the most accurate (or most reliably INACCURATE) meter so that I could maintain my INR in range, and have confidence that it actually WAS in range.

Yes, I ran a lot of tests on a variety of meters, with the goal of comparing the meters to each other, and on a monthly basis, to the labs. (At one time, I was able to get two different labs to test within a few hours of each other, and got a considerable variance between the two).

Unlike you, I don't have absolute faith in CoaguChek XS. In my experience, they've always seemed to be RELIABLY higher than my Coag-Sense meter, and the labs. For me, a 2.0 from a CoagucChek XS would be a bit scary -- it may reflect an actual INR that is .2 or .3 BELOW 2.0.

As far as 'obsessive-compulsive', if you have read my other posts, I concluded that my Coag-Sense is the meter that I will use for my testing because it is either quite close to the lab result, or slightly below it. For me, having a 2.0 on the Coag-Sense, and an actual 2.2 or 2.3 on the labs doesn't bother me. I would rather have a meter that UNDERREPORTS my INR than one that OVERREPORTS it. I'd rather risk a bit more bruising than another stroke.

I'm not looking to muddy the water for newbies. I rely on my meter, and the monthly blood draws are a bonus. I wouldn't be without my Coag-Sense meter. However, having a newbie (or others) manage their dosing based on possibly erroneous results isn't doing them a great service.

(BTW -- weren't you the one complaining about the weekly fingerpricks and monthly blood draws?)

 

[river-wear]

I'm a newbie and very much appreciate Protimenow's analysis. Assuming I go with a mech valve, I want to buy the "best" meter available. It's also good to be reminded that the results can vary a bit from actual so as not to run too close to the edge. (To clarify, the 1.8 lower limit mentioned by my surgeon is for the latest and greatest valve.)

All that said (not to minimize Protimenow's serious InRatio issue), I would expect that any serious deviation from actual INR would be cause for the FDA to re-evaluate the monitor manufacturer's right to sell them. Is there any documentation along the lines of a calibration certificate provided with the machines that says how their readings will compare with established standards? I will plan to chart my test results against the lab over time to see if there is any drift, as well as to see its tendency to read high or low. (I have a background in manufacturing and gage reliability so I understand how the statistics work.)

 

[Agian]

I'm a newbie and very much appreciate Protimenow's analysis. Assuming I go with a mech valve, I want to buy the "best" meter available.

Yep :thumbup:

 

[Protimenow]

There's a website (I'll have to get the specifics) that lists recalls and complaints about medical devices. As I recall, someone said that the InRatio was tested against CoaguChek XS results when the FDA was working on approval for the device. (It could have been against the CoaguChek S, I'm not sure). This test relied on the accuracy of the CoaguChek device that it was being compared to -- if there was allowable deviance (I'm sure that there must have been) from the XS (or the S), and it was acceptable for the S (or XS) to be within 30% of lab values, the compound error could be considerable. In my testing, the InRatio results were SO MUCH higher than the lab that I stopped using the InRatio entirely.

Both the InRatio and the CoaguChek XS have a history of displaying higher error rates with higher INRs. It's a known issue, and has been reported many times. It's part of the nature of the way that the testing is done.

The meter that I trust the most - primarily because its results are sometimes BELOW those of the lab (and almost always, if not always lower than the XS) - is the Coag-Sense. The Coag-Sense uses a physical method of determining prothombin time (there's a wheel inside the strip. When the blood is dropped into the collection well, it mixes with reagent and starts clotting. When the wheel stops spinning, because a clot prevents it from turning, an optical sensor detects the clot and the onboard computer calculates INR and displays the actual prothrombin time). The other meters rely on other methods (resistance or impedance, or something, that changes when blood clots).

As far as maintaining test results -- I keep a spreadsheet (as do many others on the forum), with date, time, dose, INR and Prothrombin time. My spreadsheet also has a column that lists the meter (or lab) on which the test was made and any other factors that may have had an impact on the INR. (These factors may include dietary changes, medication changes, illness or excessive exercise, or anything else that may be of interest). The spreadsheet is useful for historical perspective and can also come in handy as proof that you're able to self test. It may be helpful if, some day, you choose to do your own dosing management and want to convince a prescribing physician that you know what you're doing.

And, in terms or my issue with the InRatio - it may be that, for me as an individual, the testing method used by the InRatio just doesn't work for me for some unknown reason. Also - unless some serious problems are reported, the FDA may take its time before banning a device.