Home monitoring ... I'm sure I'm doing it right, but ...

[Phil]

Hi All,
I have been home monitoring for about 6 weeks. Since this time my INR has been 2.4, 2.5, 2.8 and 2.5 and I have been taking 5 mgs of warfarin each day. Before this time I was lab testing and really struggled to get my levels to stay within range. (I think the lab was under prescribing warfarin as the doses generally ranged between 3.5 and 4). I feel really pleased my levels are now consistently within range and stable, but I have a slight fear that perhaps I'm not doing this right. To put this to the test on two occasions on the day I lab tested, I home monitored tested, and the difference between the two readings was point 1 (eg - 2.6 versus 2.5). I think I just need to relax and not over work this - what do others think?

Phil.

 

[Sten Osis]

Re: Home monitoring ... I'm sure I'm doing it right, but ...

I would think that the 0.1 variance between tests is within the range of measurement uncertainty for both instruments. In other words, I wouldn't sweat it.

 

[dick0236]

I think you are doing it right since your INR values are within .1 of the lab. I have a simple test that I do ever so often.....I test my wife, about once per year, and if her INR is around 1.0, I know my meter is OK. After you get a little more experience, you will be more comfortable. I assume your range is 2-3......and 2.4,2.5,2.8 and 2.5 show your dose in right. Congratulations, you are now an expert!

 

[Protimenow]

Phil: You didn't indicate which type of valve that you've got ticking around in your chest. Personally, with my St. Jude, I am most comfortable in the 2.5-3.5 range.

With a meter that is within .1 of the labs, you should consider yourself very fortunate. I've been testing for more than four years, and over the past 16 months or so, my INRs, using whichever meter I test with, haven't been that close to the lab results.

In the thread about a new meter - the Coag-Sense, I wrote about tests comparing the meters to each other and to the lab. I also wrote about variations in values from one lab to another.

It certainly sounds as if you're dosing and testing correctly. I assume that you test weekly (if not, I think that you SHOULD). I hope that you're keeping your test results, dosing, and other possibly relevant information on a spreadsheet so that you can refer to it later (and use it to demonstrate to medical professionals that you're able to self-test and have a good idea of what you're doing).

Welcome to the growing club of self-testers.

 

[chaconne]

Being within 0.1 is VERY good and I would consider it an insignificant error. I've had 5 measurements of lab vs. my InRatio2 and they have averaged 0.1 difference.

 

[Freddie]

Your just fine - don't over think this and relax.
And you don't have test every week unless your doctor has told you otherwise.

 

[pellicle]

Hi
well I'm going to agree with what everyone has said, but I'll add a few questions (and probably repeat more or less the same.

Hi All,
I have been home monitoring for about 6 weeks.

so, not long really ... just learning the ropes. Good to see you here asking questions an venting your frustrations. I wish I'd had similar when I started. But I didn't.

Since this time my INR has been 2.4, 2.5, 2.8 and 2.5

so pretty dam stable is what you're saying. Here is my data (graphed) from this year so far...

and I'm by no means "unstable"

and I have been taking 5 mgs of warfarin each day.

which is good to note, for your own records, but in general is meaningless as a number. We all require different doses depending on our metabolism and genetics (which determines our metabolism).

Before this time I was lab testing and really struggled to get my levels to stay within range.

and this is a good time to ask ... "what is your range"

I feel really pleased my levels are now consistently within range and stable, but I have a slight fear that perhaps I'm not doing this right.

might have been better to put that earlier ... like nearly first thing ...

I home monitored tested, and the difference between the two readings was point 1 (eg - 2.6 versus 2.5). I think I just need to relax and not over work this - what do others think?

well such a variation between measurement methods is to be expected. This is not like measuring a bit of steel with a micrometer. This is chemistry. Worse, its biochemistry! Measuring the effects of things which are essentially very delicate living systems. Imagine you took a set of measuring calipers to each tomato in the box and measured them .. while at first they may all look the same size when you start writing the numbers down you'll see variations. Yet these tomatoes at the supermarket have already been sorted and graded to fit within a range.

The reason you have a range (and not a number) is that this area is imprecise. Anywhere within that range will be fine. Meaning that your specialists know that withing what is reported between those two numbers will give you the best anti-coagulation therapy from the drug.

so yes, chill

you're doing fine

Lastly, as a word of advice don't over steer corrections as they occur. Careful reading of my graph can show you the results I have had with making course corrections earlier than they were needed. There is a natural cycle (like a biorhythm) where your INR will vary in responce to the amount of warfarin in your system. That's OK ... just let it. Its only when you go out of range for a significant period (and it looks like its not coming back in) that you may wish to adjust dose.

If you know how to sail a boat its much like that. If you keep correcting the course with every gust of wind, you'll never sail straight.

 

[big_L]

I'm sure 0.1 is within the acceptable error of the meter. You could check this by running a few tests at the same time using your meter and seeing how much they vary.

At work (I'm an analytical chemist), I would run 10 or 20 replicates on the same sample then estimate the acceptable error as 3X the standard deviation of the replicates (sorry - I can't help myself).

Here's my data. I'm a newbie, so I don't have a good data set like pellicle. You see that the lab and home results aren't always the same.

 

[pellicle]

Hi

I'm a newbie, so I don't have a good data set like pellicle.

gee I dunno about that. I'm just a newbie here too. I've only been doing this since late 2011 ... there's folks here been doing it since home testing started (something like 2005 or something).

Here's my data. You see that the lab and home results aren't always the same.

That seems pretty tight correlation to me ... I have a quick question if you don't mind. I see that the red and blue dots are separated by a couple of days. Is this time the sample time or result time? Basically I'm curious to know if you you have had lab tests done on the same days as you do your self tests. Because the INR's seem to correlate really well (suggesting your INR variation is really low).

For instance I tested this Sat AM and got 2.2 (which is on the edge of my range, and a drop from 2.7 the week before (I've just updated the image that graph above points to with my latest data (and cleared out the place holder data for future data points). Looking at the trend it would seem that my INR may be on a slope down (and about to head out of range).

But (being curious) I decided not to adjust dose and tested again this morning (Tuesday). I found that it had lifted back up to 2.5 without any intervention (which isn't on that graph, I keep a separate "ad hoc monitor" sheet for them) . So I'm glad I kept things 'steady as she goes' irrespective of where the bow happens to be pointing on any given sample.
(PS: the thin blue line is a 3 period moving average trend line ... just in case anyone wondered what it was)

 

[Protimenow]

I've got a real problem with Freddie's statement that 'you don't have test every week unless your doctor has told you otherwise.' Warfarin is a medication that has a 3 day half-life. If there are any significant changes that may cause your INR to spike or to drop, waiting more than a week to test will not show these INR changes. For most valvers, having an INR BELOW range (and, in my case, for example, BELOW 2.0) for a week or more can create a high risk of stroke.

For me, even if my INR remains in range most of the time, I am not comfortable with the monthly testing that my anticoagulation clinic is happy with. I usually test every week -- sometimes, if I'm really negligent, I'll let it run to 10 days. However, I believe that weekly testing is the only way to be certain that our INR remains in range and that can alert us to problems before they become life-threatening.

Many (or should I say most) medical professionals are woefully unaware of anticoagulation or anticoagulation management issues. My last cardiologist (more than a decade ago) was not comfortable with testing less frequently than once every two weeks. This was back at a time when the only way to get your INR was to go to a lab and get your blood drawn. Doctors are still trying to balance the hassle and cost of a patient visiting a lab to the risk of stroke or bleeding as a result of infrequent testing.

Personally, if I had a doctor who was comfortable with letting me test monthly or even every other month because my last test or two were 'consistent', I'd look for another doctor.

 

[pellicle]

Hi

Warfarin is a medication that has a 3 day half-life. If there are any significant changes that may cause your INR to spike or to drop, waiting more than a week to test will not show these INR changes.

Just on this point my documents suggest that

"the effective half life of Warfarin in the body ranges from 20 to 60 hours. However the full anticoagulation effect may not be achieved until 72 to 96 hours after dosing."

so while the drug is being eliminated the effect of that dose is delayed.

I feel that this would lead to a crossover where you may not be sure of the results from the effect for a while (as I've done in the above chart). The blue line is a half life and the orange is an estimation of the increase in effect as described. This makes for a complex model to interpret effect. I guess this pretty much leads to the "rule of thumb" of wait a week to see what the results are.

also (to make things vexing) there is an S and R anomeric form for Warfarin (the clearance of the R anomer is described as being half that of the S). I seem to recall that the R anomer also effected INR differently too. A good subject for me to read up on ...

PS: yep, S anomer more active in anticoagulation:
here

Warfarin is a natural product and given as racemic mixture of the R and S stereoisomers of the drug. S-warfarin is 3-5 times more potent an inhibitor of the vitamin K epoxide reductase complex, the target of action, than R-warfarin [Article:3567019]. The stereoisomers are metabolized by different phase 1 enzymes; the predominant metabolism of the S isomer is via CYP2C9 whereas metabolism of R-warfarin is mainly via CYP3A4

{actually Protime you've asked about alcohol and warfarin and this article is about that... just spotted it when searching, thought of your previous questions and thought I'd add it here ... pardon me}

and

is a racemic mixture of two optically active isomers, the R and S forms, where the S-isomer is 5 times more potent in its antithrombotic effect.

 

[Sten Osis]

Re: Home monitoring ... I'm sure I'm doing it right, but ...

I just got a coaguchek last week. My doc wrote the order for test strips to cover testing once every two weeks. I hope that's often enough.

 

[pellicle]

I just got a coaguchek last week. My doc wrote the order for test strips to cover testing once every two weeks. I hope that's often enough.

well if you felt like it, you could always buy another pack of 24 and test yourself weekly. Its about $6 a test when you buy the strips online so you could easily just do it and see for yourself if you obtained more useful information that way.

might be that for you that fortnightly testing is sufficient ... sure is better than monthly ;-)

I wouldn't panic about it though

 

[Protimenow]

I'm not entirely sure if I've asked about alcohol -- but it's good to have additional articles. I recall reading that something in red wines has an effect on INR, so drinking a LOT of red wine may be a reason for testing the next day, just to be on the safe side.

Mike -- I agree that testing every two weeks is certainly better than testing monthly, but Pellicle's suggestion that you buy more strips so that you can test weekly is also a good idea. Consider the $12/month (if you alternate between the insurance-supplied strips and your own) versus the costs, both in money and disability, from a stroke or bleed if your INR takes a funny change between bi-weekly tests. I don't mean to alarm anybody, but as a person who went for extended periods between tests -- and who was pretty damned lucky not to stroke or bleed out in the interim -- I am firmly convinced that weekly is really the best way (even if I don't always follow this rule and sometimes go as long as 10 days between tests).

Also, FWIW -- if you DO get your own strips, use up one supply before starting the next so you don't have to worry about swapping code chips into and out of your meter.

 

[Bina]

Hi All,
I have been home monitoring for about 6 weeks. Since this time my INR has been 2.4, 2.5, 2.8 and 2.5 and I have been taking 5 mgs of warfarin each day. Before this time I was lab testing and really struggled to get my levels to stay within range. (I think the lab was under prescribing warfarin as the doses generally ranged between 3.5 and 4). I feel really pleased my levels are now consistently within range and stable, but I have a slight fear that perhaps I'm not doing this right. To put this to the test on two occasions on the day I lab tested, I home monitored tested, and the difference between the two readings was point 1 (eg - 2.6 versus 2.5). I think I just need to relax and not over work this - what do others think?

Phil.

Hi Phil,
I see from your profile that you are an AVR "expert" and we share the same Regent valve.

Regarding your INRs-----THEY ARE PERFECT, GOOD FOR YOU !

During the first few months post op it is a very good idea to test at least every 2 weeks if you have a steady diet and routine, or weekly if you or your doctor think it is necessary.
I've been home testing for over 6 years and do my test every 2-3 weeks. My INRs are quite stable.
Sometimes it is just a matter of getting used to your new routine and then you will relax, but i remember being very nervous about the 'unknown'.

 

[Bina]

I just got a coaguchek last week. My doc wrote the order for test strips to cover testing once every two weeks. I hope that's often enough.

Yay---Coaguchek

I order 24 test strips for the year , and test every 2-3 weeks. You should be fine, unless your INR needs adjusting, then you may need more frequent testing.
Enjoy !

 

[Protimenow]

How is it possible to know what happens to your INR during the time between testing, if you only test every 2-3 weeks? I've been testing weekly (or almost weekly) and have detected changes that occasionally require slight dosing adjustments, and that would have been completely missed if I tested every 2-3 weeks.

To me, the extra $150 or so each year for enough additional strips to enable a weekly test seem to be a whole lot less than the cost of treatment for stroke or hemorrhage.

Taking an INR is something like taking a photograph of cars on a racetrack. If you time the photograph so that it always catches the car when it is right in front of you, you will be led to conclude that the car is standing still. More frequent photographs may show the car (your INR) in a much different place. An INR test every 2 or 3 weeks doesn't give you a true picture of what may be happening to your INR between tests.

The risk of stroke goes up significantly (I KNOW) if your INR is below 2.0 for a week or more. If your INR drops to this dangerous level right after you test your INR (and it's not impossible for this to happen - dietary changes, a forgotten dose or two, and other factors could produce this result), you might be in danger and not even know it. A weekly test will give you enough time to respond to unexpected drops or spikes.

 

[big_L]

Pellicle - You're right, I usually do my testing on Sat or Sun with lab testing then on Monday. So, I really can't say that I'm just looking at testing variability, the day-to-day variability is there also (confounded - as the statisticians would say).

 

[Protimenow]

When I get my lab tests, I usually do my self-testing at home an hour or so before the blood draw. I know of some people who actually test on their meters when they are IN the lab, or when they get to their cars. Although this may be taking things to the extreme, testing a day or two before a blood draw won't really give you a reasonable basis for comparison (as you've already noted).

 

[Phil]

Hi All,
Thanks to all who responded. I reckon I feel pretty ok about what I'm doing - testing at about the same time each Sunday, staying within range (2.0 - 3.0), eating a consistent amount of greens each day, keeping a log of results, etc. I'm by no means an expert, but feel home monitoring, and warfarin in general, is not the monster I had concocted it to be. Touch wood, I have settled into a good groove and the stability I am experiencing will continue.

A big thanks to Bina - you response was encouraging and heart felt.


Phil.