the 15 second rule

[Protimenow]

I've found that my InRatio is typically .3 or more higher than lab. My ProTime is sometimes closer to the lab, but the lab isn't always exact (even if they give the values in hundredths). Personally, if the InRatio gives me anything from about 2.8 - 3.9, I consider myself to be in range.

As far as doing a bit of a squeeze on the finger to get a big enough drop - this should be okay -- it's when you 'milk' the fingertip, adding in a lot of serum, where the accuracy of the meter may drop.

 

[pellicle]

Anyone who has a few years experience on INR testing .

Indeed this is with almost any biological testing. Its always prone to variances and inconsistencies

 

[pellicle]

I've found that my InRatio is typically .3 or more higher than lab.

About the range of variance I see too. Interesting

 

[Protimenow]

A while ago, one of the people on the forum worked out an algorithm for predicting what the lab values would be, based on a value determined by the InRatio. He revised this a couple times. If I recall correctly, one of his attempts at making this determination is taking the InRatio value to the power of .85 (something that can be done with a scientific calculator or with the right calculator on your computer). Of course, the labs don't always agree with each other, either, so this won't always work. An important part of this is realizing that the InRatio value is always higher than the one reported by a lab. Therefore, shooting a bit higher than your range may be the safest place to go, if you use InRatio -- my range is 2.5-3.5, I usually look for around 2.9-3.9 or so. (This is not a recommendation - just a personal range. When I can, I occasionally validate with a blood draw, or try to correlate to a test on a ProTime meter)

 

[lance]

The test result is just that. INR management is not rocket science although some here try to make it so. Until either of us experiences a TIA caused by "rocket science" methods of management we prefer to employee the kiss principle--KEEP IT SIMPLE STUPID.
Obtaining a large enough blood sample is no longer the challenge it used to be. It just took a little practice.

 

[newmitral]

Hi Protimenow,

An important part of this is realizing that the InRatio value is always higher than the one reported by a lab.

That is a very misleading statement to make, and others reading the forum should not accept that as generally true for them.
For certain individuals, there may be factors in their particular blood that cause the meter tests to be biased slightly higher than lab test results. For others, there may be factors that cause the meter tests to be biased LOWER than the lab results. But, on the average, over a large population of test subjects, the meters must be designed to give the same average results as the lab tests. If this were not the case, the meter manufacturers would readjust the meter calibrations to be more accurate.

The only way for any given individual to know if there is a particular bias on the high or low side for their specific individual blood is to make many comparisons over time between meter results and lab results.

I believe PEM was the user you refer to in the prior thread, and he had made many such comparisons for his specific test results.

I have also made a few comparisons between meter and lab tests, and i have concluded that for my particular blood characteristics, the meter is in excellent agreement with the lab draw results. There is no consistent bias either high or low. In fact, for the test comparison I just made about a month ago, the Inratio-2 was 0.1 LOWER than the lab test result (2.8 v 2.9). So I can say with certainty that for me, the Inratio is NOT always higher than the lab result. I am continuing to gather statistics, with a lab draw INR test every 6 months or so, when I'm going to the lab for other blood tests my doctor wants to do as part of general physicals.

So, it is not a good idea to give readers of this thread, especially if they are new to home testing, the idea that the meter will always be biased either high or low for them. On average, for most people, the meter should be accurate within the allowable and expected test variations.

You might also want to consider these two statements made in this tread in juxtaposition:

As far as doing a bit of a squeeze on the finger to get a big enough drop - this should be okay

and

I've found that my InRatio is typically .3 or more higher than lab.

Perhaps there is more of an impact from squeezing the fingers than you realize.


But, even more important is that the risk profile for adverse incidents versus INR is quite broad, and the meters don't really have to be that accurate to do their job. The risk of stroke only increases very slightly when you drop from INR of 3.0 to 2.0, or even 1.5 if you look at the data from several studies.
So, with a target range of 2.5-3.5 like I have, even if my meter were to be off by 0.5 (although it's not) it wouldn't make any significant difference in overall risk of adverse events if I stay within range per my meter's results.

Please note that even if you are perfectly anti-coagulated there is still some residual risk of adverse events, so being in range is not an absolute guarantee against stroke, it just minimizes the risk.

 

[tom in MO]

My Allere trainer indicated it was OK to squeeze the finger to be stuck, with the thumb of the same hand, with a "milking" motion similar to what you would do to the teat of an udder. She said not to squeeze it very hard, or to squeeze it in one place. Also, I was to keep the hand hanging at my side. The heat of washing your hand, followed by gravity and a gentle squeeze was the concept.

In my training lesson, the new monitor was compared to her monitor. IIRC they usually within 0.2 INR but have to be within 0.3 INR.

 

[ElectLive]

But, even more important is that the risk profile for adverse incidents versus INR is quite broad, and the meters don't really have to be that accurate to do their job. The risk of stroke only increases very slightly when you drop from INR of 3.0 to 2.0, or even 1.5 if you look at the data from several studies.
So, with a target range of 2.5-3.5 like I have, even if my meter were to be off by 0.5 (although it's not) it wouldn't make any significant difference in overall risk of adverse events if I stay within range per my meter's results.

Please note that even if you are perfectly anti-coagulated there is still some residual risk of adverse events, so being in range is not an absolute guarantee against stroke, it just minimizes the risk.

While the broad points here are sound, I think some caution should be in order about potentially overemphasizing lack of effect on adverse events. Yes, while the risks are very low overall in any circumstance, including those temporarily outside the normal INR range, there is still a measurable and significant effect, particularly with numbers as low as 1.5. Now, like anything, some patients, the vast majority in fact, may and will be just fine drifting out of range temporarily. Others however will not, more likely the higher risk patients, one would assume.

So, I think the more telling measure of INR control on adverse events is not so much the overall low rate of events, but the percentage of time adverse events really happen when outside of range. Even more critical at the high end of the range too, for bleeding events, where the effect is usually much more pronounced. Take the ON-X Proact study as one example, a very recent and tightly monitored and controlled group, all with same valve, using home INR monitoring, etc. The majority (anywhere between 50% and 70%) of adverse events are occurring in patients who are outside of their target range (both control and study groups). Of course, patients only stay in range about 70% of the time anyway, at least in their data, but the mean INR values for the adverse events still prove the same point.

Anyway, sorry for going even further off track here, and again, back to the big picture, I agree with the broad points overall. But reading through, I just thought it's important to be careful about not discounting too much the importance of staying in range, particularly for those who might have other risk factors making it much more important an issue. 1.5 does not align with 3.0.

 

[mecretired]

I have a Coaguchek XS and have been using it for about 1 1/2 yrs. When I compare the results with the lab they have always been within .2. My instruction book says --after using the lancet---"Gently squeeze from the base of the finger to develop a hanging drop of blood." I understand the term "milking" to mean multiple squeezes????

 

[Julian]

I've noticed my coumadin clinic will lance then wipe then take sample. At home I would lance and skip wipe and try to squeeze out a sample. The other day at home I tried the wipe technique and immediately after wipe got a generous sample quickly. Anyone try this?

 

[Protimenow]

No, definitely not rocket science. With self-testing and sensible dosing management, it's not much of a deal for many of us. But try convincing certain medical professionals (and coagulation clinic personnel) that this is actually something you can do -- and do it as if your life depended on it. You may get the same kind of crap that a clinic tried to feed me -- "if you self-test, we won't service you" "monthly testing is just fine if your two previous INRs were in range' 'you can't possibly self-test if your meter hasn't been calibrated' 'we've been doing it this way for ten years, so it must be working', etc.

BTW -- I plan to test the fifteen second rule in the next day or so. I have an InRatio and an InRatio2. I will use the FIRST drop, obtained within fifteen seconds of incision, then wait a while and use the second drop on my second machine. I'll report on the results of both. (Of course, this will only relate to my one time test on two slightly different machines, but it'll be interesting to see if there is any substantial difference).

 

[pellicle]

BTW -- I plan to test the fifteen second rule in the next day or so. I have an InRatio and an InRatio2. I will use the FIRST drop, obtained within fifteen seconds of incision, then wait a while and use the second drop on my second machine. I'll report on the results of both. (Of course, this will only relate to my one time test on two slightly different machines, but it'll be interesting to see if there is any substantial difference).

good idea! Testing!

I will also publish my results

 

[tom in MO]

I guess milking may not be the best term. I really mean consecutive squeezes, starting at the first knuckle and pushing down towards the finger tip.

 

[JimL]

Maybe I was distracted by all this discussion, but it took two strips and three fingers for the regular test this morning. However, I can report that my INR was well within range, and the 15-second rule never came into question; it was more like 5 seconds.

 

[pellicle]

but it took two strips and three fingers for the regular test this morning.

Interesting ... given you go on to say:

and the 15-second rule never came into question; it was more like 5 seconds.

If you produce the drop of blood within 15 seconds why did you blow the first 2 strips? The only reason I blow a strip is putting the blood on too early (before 30sec warm up completes) or because I don't get blood within the 180 seconds.

 

[pellicle]

good idea! Testing!

I will also publish my results

from the most recent tests
coaguchek Lab
2.7 2.8

 

[pellicle]

good idea! Testing!

I will also publish my results

from the most recent tests
coaguchek Lab
2.7 2.8

 

[JimL]

The first strip yielded a "5" on the meter, probably due to an insufficient quantity of blood. The second strip was, of course, successful.

 

[Protimenow]

Personally, I don't ever incise my finger until the meter tells me it's ready. Even though it may give you a lot more than fifteen seconds to deposit the drop, it still wants it before the fifteen seconds after incision are up. (Maybe they think that you may need a minute to get up the nerve to lance your finger, or they think you may need some extra time to stop blood flow out of your fingertip (by pressing on the knuckle below the fingertip) so that there's a big pool of blood in the fingertip and you'll be able to get an adequate drop. I'm not sure of the reason for the extra minute or so - but CoaguChek XS and InRatio still want that first drop within fifteen seconds.

 

[pellicle]

The second strip was, of course, successful.

ahh, this is based on my failure of reading comprehension. I had taken it to mean you blew two strips : thus required three.

I'll go back to my corner now...