INRatio vs lab differences

[jeffp]

In one of my many emails back and forth with the Hemosense folks, they sent me this tech bulletin: http://www.hemosense.com/docs/5500330_TechBull109_ClinicalExpPTRevB.pdf with regard to the differences many of us are seeing in INR results. According to WHO standards, a difference of +/- 30% in the INR range of 2.0-4.5 is within acceptable limits for error from a lab test standard. I've been seeing a stable +25% variation from my PCP's lab results (recently 3.2 lab, 4.0 INRatio). The 0.6 that many seem to be reporting would be about right for the 2.5 range (maybe a bit higher if your error is less - I think we all should have at least one lab test to gauge against, probably 2 in case the lab is off - which happens. With a box of 12 it begins not to make too much sense to keep rechecking). Has anyone found any error in the other direction? One would think that some would be reading low as well. How about differences in error from strip lot to strip lot? (I'm still working off my 1st box of 48, so I can't tell about that one yet.) Just thought I'd post this FYI.

 

[geebee]

I have never seen a test result from my INRatio that was lower than the lab test and I have gone through a number of different lots. I usually test about .4 higher on the INRatio when compared to lab. I just try to stay on the high end of my range and not worry about it. I still lab test every 6 months or so just to make sure my cardio is happy but I am fine with the results I get.

 

[Ross]

Nope, nothing lower always higher then the lab draw. I've been through multiple boxes and have not yet seen any inconsistencies.

 

[Guest]

Thanks. This is good to know.

I find that the CoaguChek is not consistently high or low compared with our hospital lab. It varies, probably in the 30% range but you can't predict which way.

Mismanagement by inexperienced people telling you what dose to take is likely worse than the lab results.

 

[Alaska]

I've brought my INRatio to the dr's office twice now to compare their Coagucheck and my machine. Both times mine was .3 higher (2.4 vs 2.7; 2.6 vs. 2.9). So far, seems consistent.

 

[Blanche]

Albert's had his ProTime for 5 plus years. In that time, he has had numerous comparisons with lab tests. Sometimes the lab was higher, sometimes it was lower, and sometimes it was on-spot. There didn't seem to be any pattern. Actually, several times we tested against another ProTime machine..one test after the other, and never got the same result.
Blanche

 

[Guest]

This proves that blood clotting is an inexact process.

 

[Philip]

InRatio/Clinic Comparison

InRatio/Clinic Comparison

I preformed my first comparison of the Coumadin Clinic and my new InRatio monitor and obtained a .2 higher reading on the InRatio. Close enough for me!

Was it coincidental that that on the InRatio my INR was 4.5 and the PT was 45.0 or does this relationship remain constant?

The finger stick is not as offensive as expected.

Philip

 

[Ross]

Was it coincidental that that on the InRatio my INR was 4.5 and the PT was 45.0 or does this relationship remain constant? Philip

The INRatio strips have an ISI index of 1, so a PT of 45 and an INR of 4.5 are right on the ball.

Fingersticks beat veinous sticks any day!

 

[RandyL]

anybody ever get a reading of .7 When I stopped my coumadin for a procedure I tested to see how my coumadin drops. Went like this:
2.5
1.7
1.1
.7

I quit testing after that, used 4 strips for 4 days. I thought you couldn't be below 1.

 

[RCB]

Always

Always

HIGHER! Up to .6 on my Protime.

 

[Guest]

The 0.6 and 0.7 readings demonstrate exactly what I have been preaching for a long time. Blood clotting measurement is not an exact science. The definition of as low as you can go is 1.0. The numbers that you get on any tester, home, commercial lab or hospital are only approximations. That is why a reading of 0.2 difference between one tester and another are meaningless. It is also why there should NEVER be big adjustments in the warfarin dose when the number is only slightly out of range.

ALL lab tests are this way. Let me give you a personal example. Many of you know that 36 months ago I had my prostate frozen out due to cancer. Every six months I have my PSA checked. Last December it was 0.3. In June it was 0.5. I was told, "This is nothing to worry about." But we all know how that goes. Two days after it was 0.5, the supervisor of the hematology department was in our clinic drawing blood to do our semi-annual comparison of the CoaguChek-S with the lab PT/INR tester. I told her that I would donate some non-warfarin containing blood if she would also take a tube to do a PSA on. She agreed. My PSA came back 0.7. Since it had "increased" 0.2 units in 6 months, it would be impossible for it to "increase" another 0.2 units in two days. Therefore, I know that an 0.2 unit variation is within the limits of the test.

So instead of worrying about two different INR tests varying by 0.2 units, I suggest that you turn your worrying to a more important topic like an asteroid that might crash into the earth and destroy all life on June 22, 2150 at 11:57 AM. Maybe if we all worry enough it will be delayed until 11:58 AM.