Labs don't match. Meters don't match. Is 'hoping' that you're in range enough?

[Protimenow]

I've written a lot about comparing meters to each other, comparing meters to other meters and, recently, about comparing meters to labs.

Now, I'm adding a bit to the discussion -- comparing LABS to LABS.

I've assumed that my InRatio was going to always be about .6 or so higher than the hospital lab. It's been this way on all the tests I've taken within an hour of the blood draw.

On Monday, I had a blood draw at two labs. The hospital lab had a 2.97 -- nicely in range for me - and within the predictable variance for the InRatio. (It was close to the 2.8 that my ProTime meter reported).

On Monday, my other blood draw was at a local clinic - and they sent the blood out to a lab to test. This one shocked me -- 3.6. It's not unlikely that the clinic lab may have mishandled the blood, or perhaps the lab's reagents were off, or something - but the question is -- with two labs testing blood taken a few hours apart coming up with such different results, WHO CAN YOU TRUST?

I'm not sure that I'll have the opportunity to compare labs again, but it sure would be interesting to do see if this difference can be replicated.

Any suggestions?


(Perhaps I shouldn't care as much -- both labs put me in, or awfully close, to being in range. But, for me, it's kind of disturbing that two professional labs can come up with such disparate values)

 

[dick0236]

Any suggestions?


(Perhaps I shouldn't care as much -- both labs put me in, or awfully close, to being in range. But, for me, it's kind of disturbing that two professional labs can come up with such disparate values)

I'd pick ONE INR testing method, using ONE device or lab, and stick with that ONE unless you get a REALLY strange number . A 2.97 and 3.6 really are not that different.....and in my opinion, would not demand any adjustments or concerns.

Most of us on this site feel that INR's between 2 and 4 are OK and would require no, or only a "tweaking" of diet or warfarin. Since the acceptable INR range is so broad, it seems to indicate that NO test, or testing method, can be considered very accurate. My personal opinion is that trying to "mico-manage" INR will drive you NUTS and is impossible to achieve.....given the current state of the INR art or science.

 

[catwoman]

I'd pick ONE INR testing method, using ONE device or lab, and stick with that ONE unless you get a REALLY strange number . A 2.97 and 3.6 really are not that different.....and in my opinion, would not demand any adjustments or concerns.

Most of us on this site feel that INR's between 2 and 4 are OK and would require no, or only a "tweaking" of diet or warfarin. Since the acceptable INR range is so broad, it seems to indicate that NO test, or testing method, can be considered very accurate. My personal opinion is that trying to "mico-manage" INR will drive you NUTS and is impossible to achieve.....given the current state of the INR art or science.

****:
Thank you!!! That's exactly what I was told nearly 9 years ago when I got my first INR monitor. I had to test my ProTime 3 against the PCP's Coaguchek, and they were 0.3 or 0.4 apart. I was told that since I was going to home-test, to rely on my meter. (My PCP's office uses a CoaguChek, rather than doing lab draws.)
I think we need to stick to one monitor and go by just that one. Otherwise, you are micro-managing your INR, as you said.

 

[Protimenow]

Thanks, **** and Marsha

I"m actually not micromanaging my INR - I haven't changed doses because of these reports, but it IS rather striking that two different labs would come up with values that are THAT far apart. (Okay, .63 isn't critical - unless they're at the bottom end of the range, but the difference is still somewhat troubling). I used to use only ONE meter - the InRatio, and the 2.5s that it reported actually put me below 2.0 (somewhere around 1.7 or 1.8), and to some degree, my reliance on the accuracy of the meter was what contributed to my stroke. (I was comfortable with 2-4, and didn't make any changes when I got those results -- but had I known that a 2.0 on an InRatio was actually more like 1.5, I'd have been concerned. At this point, I'm a lot more comfortable if my meter says something about 3.0)

Learning the meter, and its quirks in relation to lab draws, is an important part of INR management that I missed -- I believed the 2.5 to BE 2.5, when my INR was actually too low to go for weeks at that level.

If you're testing your meter against occasional blood draws -- putting your faith in a single meter is a good idea. But when the LABS don't agree, where are you? Where's the standard that you are comparing with?

(I've decided that the second lab - one at a busy clinic - probably was less accurate than the hospital lab. It was a hot day, the phlebotomist was probably doing dozens of blood draws, who knows when the courier picked the blood up, and who knows what other factors may have influenced the final result?)

No, I don't micromanage my INR - to do so would probably not only drive me crazy, but would also put me on the INR roller coaster. However, I'm still somewhat concerned about clinics or labs that use particular meters, trusting their values, and occasionally letting patients with INRs that are too low continue at danger levels. And, still, which method I trust - ProTime, InRatio, or either of two labs with widely varying results -is still not quite clear. (For now, I'll continue primarily with the InRatio, perhaps occasionally using the ProTime at the SAME time as the InRatio, and comparing the two - just out of curiosity)

 

[ElectLive]

I was researching an unrelated topic a few months ago in the European Valve Guidelines, but happened upon something that seems somewhat relevant to this topic. The European Guidelines have sets of target INR values for mechanical valve patients, much like we do here in the US. However, there is one big difference. The target INR is a fixed median value, not a range. In other words, someone being told to target and maintain INR of 2.5 to 3.5 here in the US would be told to strictly target 3.0 in Europe (assuming the Guidelines are followed, of course!). There is a brief explanation included in the Guidelines:

"We recommend a median INR value, rather than a range, to avoid considering extreme values in the range as a valid target INR, since values at either end of a range are not as safe and effective as median values."

Anyway, I was a bit surprised to read this, knowing from so many here that fluctuations are a natural part of the process, and overcompensating potentially worsens the effect. Also, I remember reading a study of patients who were managed under both a normal range (such as 2.0 to 3.0) and a narrow range (such as 2.0 to 2.5) with pretty interesting results: the mean INR trended only slightly downward (for instance it might have gone from 2.5 to 2.4) but the overall level of control (factoring in low and high values) was actually no better, due to a similar effect. In other words, it's a lot harder to stay above 2.0 if you're aiming between 2.0 and 2.5 than if you're aiming for 2.0 to 3.0. (In case you're curious, one of the On-X reduced anticoagulation trial arms has a narrow range, and that's what led me to that study at the time.)

Ok, but let me get to a point here. Knowing that fluctuations in INR are inevitable, and that inconsistencies in INR measurement (especially for you Protimenow) also happen, in some ways, the European approach starts to make more sense. Your post about feeling more comfortable now at 3.0 seems to touch on this. Of course, while it may make sense in theory, in practice, not so much, for the reasons mentioned above. But maybe it's more an issue of slightly longer term trajectory...in other words, making a point to not "hover" at the edges of the range?

Now, I haven't really helped at all, just sort of offering up random thoughts, but I do have one concrete thing to mention. The related thread that our member Pem started a few months ago, or many months ago, whenever that was, I remember that he also did comparison lab testing. If memory serves, his lab results were nearly identical (maybe .1 or .2 apart), it was only the home meter to lab values that were significantly off for him. In fact, I even remember that he had done a comparison of the lab's ISI values too which were much more dramatically "off" than the actual INR results, so in other words, the calibration and measurement process seemed to be working well for him at those particular labs. In comparison, your experience certainly suggest that something is not what it should be at one or the other lab.

So anyway, don't know if his posts at the time will help at all, or maybe he'll see this thread, but there is at least one other member who's been down this road. I don't envy your position getting to the bottom of all of this, since for you it seems to be still an issue of figuring out which is your single source to really trust, but good luck in your efforts!

 

[dick0236]

But maybe it's more an issue of slightly longer term trajectory...in other words, making a point to not "hover" at the edges of the range?

Thanks for your post. Your phrase, above, is the crux for successfully dealing with ACT.....for me. For many years after the introduction of the current INR system, I tested without keeping my own record of the test results and found that my docs were "reacting" to a single test result that tended to keep me on a roller coaster. Only after I began keeping my own INR history, with footnotes, did I begin to consider the "INR trend" and not the single number.....and make adjustments only when I "hover at the edges of the range".

I guess I try to shoot for a single target number of 3+, but am OK with any number between 2.2 and 3.8, so long as I do not stay at those fringe numbers for more than a test, or two. My last "hovering" experience was a few months ago, when my numbers began to "hover" at the low end......turned out to be a change in warfarin lab(Taro). I switched back to my previous lab(Barr) and my numbers immediately returned to 3+. That experience even took my doc by surprise.

 

[Protimenow]

Yes, some of these earlier threads were very interesting -- especially the one with a formula for predicting lab values from InRatio results. (If I recall correctly, one of the algorithms was that lab value = InRatio to the .85 power)

I chose not to trust the lab that gave me the 3.6 INR result. I'm more comfortable with the 2.97 from the hospital lab. I also have some doubts about how well the clinician who gave me follow-up advice on dealing with INRs that are out of range was trained. Personally, even at 3.6, I probably would not have changed my dose of warfarin - it's too close to range and would probably fluctuate back into range - and adding a green or two to my diet (yuk) would also bring it down. My clinician's advice -- reduce my daily dose on Sunday to 1/2 dose. This clinician was probably using the guidelines that were based on weekly totals -- her suggestion, of course, made little sense to me. If I take 1/2 dose on Sunday and test on Friday, the results of the change on Sunday would be gone -- so what's the point of a change ONCE in an entire week? These people just aren't adequately trained -- and the guidelines are not clarified for these poor, overworked clinicians.

---

I plan to trust my InRatio (and 2) to be 'reliably' between .3 and .6 above the lab. As long as my values are between 2.9 and 3.8 (or so), I figure that I'll be near the 3 that is recommended in Europe.

 

[Bina]

I'd pick ONE INR testing method, using ONE device or lab, and stick with that ONE unless you get a REALLY strange number . A 2.97 and 3.6 really are not that different.....and in my opinion, would not demand any adjustments or concerns.

Most of us on this site feel that INR's between 2 and 4 are OK and would require no, or only a "tweaking" of diet or warfarin. Since the acceptable INR range is so broad, it seems to indicate that NO test, or testing method, can be considered very accurate. My personal opinion is that trying to "mico-manage" INR will drive you NUTS and is impossible to achieve.....given the current state of the INR art or science.

Ditto.....Ditto.....DITTO.
Keeping my INR around 3.0 ( in the middle of my range) works for me Coming up on 7 years of perfect tests.