Which Meter?

[Protimenow]

Boy, things are sure getting interesting.

People who followed my thread would have read a few months ago that I had a TIA (the doctors called it a stroke). I was testing with an InRatio, and was at the bottom of my range.

When I was in the hospital, my INRs were 1.7 (when they first tested me) and 1.8 (the next day, after a larger dose of Warfarin). My meter, at home, said 2.6. This was in range, according to the meter, but dangerously out of the range (as evidenced by my TIA) according to the lab.

I was still inclined to trust my meter - until the lab values were consistently .5 - .7 below what my meter told me.

I called Alere, and they told me to 'trust the lab.' I don't have Thalessemia or Hematocrit problems (as far as I know), so I don't have these issues that would result in a testing error.

I replaced my ProTime 3 with an InRatio, and the relative ease of use, and compact size made me want to switch over.

Lately, though, I've been thinking that the ProTIme 3 may be more accurate than the InRatio. It's built by a company that makes lab quality testers. The one time I correlated a test with the lab it was almost exact.

I felt that switching back to ProTIme 3 made sense.

Now, I'm not so sure.

A week ago, I tested my blood using the InRatio and the ProTime meters. (The process is simple - incise my finger using the ProTime lancing device. Put the first, big drop of blood on the InRatio strip, wipe the finger, then put the rest of the blood into the ProTime collection cup).

Tests that were done minutes apart revealed a 3.5 in the InRatio, and a 2.4 from the ProTime 3. The lab, with a blood draw an hour or two after the InRatio/Protime tests, was a 2.95. This value was almost an average of the two meters.

Today, I retested and had similar results -- 3.4 from the InRatio, and 2.4 from the ProTime 3. I'm not concerned about going out of range using results from either meter, but it's disturbing that there is so much difference from one meter to the next.

The question, I guess, is 'which meter (if either) should I trust?' Perhaps I should just be happy with an average.

Any thoughts would be appreciated.

 

[hook]

My meter is a coagucheck and it is always .4 to .6 above the lab. As a mater of practice I take a 2.5mg booster when I get below 2.8 when trying to keep a range of 2.5 to 3.5.

I think it is important to know your meter by doing a lab draw when the opportunity comes up and check it the same day with your meter. Track the variance and use the average as the number to add or subtract from your meter meter results.

As long as your meter is consistent with the gap between reading lab results this will work. If you meter is all over the place you should get it replaced.

 

[Protimenow]

Yes, it's good to know your meter. It's also important to occasionally check it against lab results (assuming, of course, that the lab is always right). Of course, a meter may not always reliably vary by the same amount. If your meter says 3.0, it would be nice to assume that the lab value is 2.5 (assuming that the meter is giving values of .5 above the lab), but if your meter says 4.1, is it safe to assume that the lab will be 3.6, or is the meter's variance higher as the INR climbs?

The one time in the past that I had the ProTime checked against a lab, the values were almost a perfect match. Now, with a variance of roughly 1.0 between the InRatio and the ProTime, it's certainly comforting to assume that the ProTime is .5 below the lab, and the InRatio is .5 above the lab, but I don't have enough data points to conclude either way.

What may be even more troubling is that labs and clinics USE these meters and RELY on the accuracy of the meters for making therapeutic decisions. In the past, I relied on my InRatio to give me accurate results. I know that clinics often run correlations with the labs - or run the tests against a known standard -- but it does concern me that many of us are betting our lives on the accuracy of a meter.

(And, yes, when I had my blood drawn, it was always within an hour of tests using one or more meter)

 

[Protimenow]

It's only getting worse.

Today, my Protime gave me a value of 2.0. The InRatio was a 3.3. The difference between the two is fairly consistent -- and if I take an average of the two, I'm right in range.

ProTime's tech group didn't answer my e-Mail about giving a lower than lab value; InRatio in the past said to trust the labs. I was under the impression that the ProTime meters don't require calibration -- perhaps they do. (I have an older ProTime meter - maybe I'll test on it and see what IT tells me. If it doesn't agree with the ProTime 3, perhaps one or the other - or both - are off).

Short of a blood draw, I may wind up concluding that the InRatio is more 'reliable' - regularly reporting .6 or .7 higher than the labs. Perhaps the ProTime is also reliable - consistently reporting .5 - .6 BELOW the labs. It would certainly be good to have ONE meter that is CLOSE to lab values.