May be of use to newbies self testing/dosing

[UncleSteve]

After 15 years of visiting my INR clinic I've decided to self test. However my forward thinking (*not*) local health authority has told my GP that if I follow my chosen route, they will not support me, hey ho... So I've been looking at various methods to guide me through dosing.

There are some software programs around (still researching), however I came across a paper/card slide rule type calculator which was fairly cheap, but the shipping to Europe was £28.46 (GBP) = $44.95 (USD - can, so complained to Amazon who fobbed me off, so went to the publisher and complained and after waiting a week or so, they dropped the shipping down to £10.78 (GBP). So for the total order value of £16.47 I've ordered one to see what its like. Perhaps this may well interest a few people in the UK and Europe now I've got them to be sensible with their shipping.

I've come across a few on-line dosing calculators, and quite a lot of software aimed at clinics and organisations with huge prices to match. Just wondering if anyone uses a pre-written program apart from the obvious spreadsheet program Excel?

Steve.

 

[pellicle]

Hi Uncle Steve

After 15 years of visiting my INR clinic I've decided to self test. However my forward thinking (*not*) local health authority has told my GP that if I follow my chosen route, they will not support me,

they can be like that ... only your best interests in mind.
*cough

however I came across a paper/card slide rule type calculator which was fairly cheap, but the shipping to Europe was £28.46 (GBP) = $44.95 (USD - can, so complained to

do you have a link to that?

I'm curious, does it ask for such things as your VKORC1 or CYP2C9 genotype? If not then I would expect that its "a wide guideline" and not really ideal to be trusting.

I'm a big fan of empirical evidence, and if you've already been on warfarin for a while then you'll have a bucket load of it already (as long as you've been documenting). I totally recommend anyone who's self dosing to be keeping scrupulous records. Doesn't matter if its a book, a Spreadsheet or whatever ... just as long as you have the records.

As I understand it the critical time for issues is when starting warfarin therapy. I switched over to self testing after about a year with a clinic. I'd been keeping records of their doses for some time. Then when I thought "ok, I can do this as well" I started taking a blood reading with my coagucheck XS as soon as I got home from the clinic (sometimes before I went in).

Once I was then confident with my self testing technique (which I honed further after taking over as well) I already had a good guide as to what to do and how to adjust.

A friend of mine does computer machining and engraving, one of his favorite sayings is:

automation should never be unattended

Having some background in computer modeling I can only agree with it. To me the best software is "decision support" where software like Excel graphs your data to help you see the things and make your own decisions.

I do have a journal article somewhere where a few years ago a researcher was doing work to tweak the clinic base software tools should you want me to dig it out, but even they fell back on an experienced clinician reviewing the doses.

Best wishes for your own management. I'm sure it'll work out both more convenient and accurate.

 

[pellicle]

some quotes from the journal article: which makes me think that if anyone is going to

1. go to the effort of paying developers to develop software
2. potentially take on the law suits
3. desire to make a profit

that its not going to be 'cheap'. Anything that is 'cheap' may just be that. Still there could be something on sourceforge ... I should have a look at that...

We conducted a double-blind randomized controlled trial among 712 patients with an indication for long-term anticoagulant treatment at the Leiden Anticoagulation Clinic. We compared oral anticoagulant dosing supported by the new algorithm (ICAD) with the standard algorithm (TRODIS).

The percentage of time spent in therapeutic range was similar for the new and standard algorithm group, 79.8% versus 80.2% (Diff 0.4%, 95%CI –1.7% to 2.6%). The new algorithm produced a dosage proposal in 97.5% of visits and the standard algorithm in 60.8% (Diff 36.7%, 95%CI 35.4%-38.0%). 79.3 % of proposals of the new algorithm were accepted by the physician versus 90.9% for the standard algorithm (Diff 11.6%, 95%CI 10.2%-13.0%). This implies that the new algorithm gave an acceptable proposal in 77.4% of all patient visits versus 55.3% for the standard algorithm (Diff 22.1%, 95%CI 20.4%-23.8%).

The use of computer algorithms to assist physicians with their dosing decisions has been shown to lead to equal or improved quality of control of oral anticoagulant treatment compared to unassisted dosing [2-6]. Several algorithms have been developed previously. Poller et al. compared three different computerized systems to assist warfarin control to traditional dosing by experienced doctors. They found roughly similar results for unassisted dosing by physicians and dosing by the three algorithms [7]. In a larger multicenter study Poller et al. evaluated the safety and efficacy of the DAWN AC anticoagulant therapy management system. They found that patients in the computer-dose group spent more time in the target range than patients in the traditional-dose group [8]. An algorithm that is similar to these algorithms is used widely in the Netherlands (TRODIS) [9]. This algorithm generates a dosage proposal in approximately 55% of visits, leaving 45% for unassisted dosing by experienced physicians. In approximately 20% of cases where TRODIS generates a dosage proposal, it is overruled by a physician [10]. All these algorithms are based on an empirical decision-tree that determines whether the same dosage can be maintained, dosage adjustments have to be made or manual intervention by a physician is required.

A major disadvantage of these algorithms is that they do not generate a dosage proposal in all cases and they do not take into account the sensitivity of the patient for coumarin derivatives (which may change over time), the half-life of the drug, and the non-linearity of the dose-INR relation.

The Improved Control of Anticoagulant Dosage (ICAD) algorithm is based on a model that comprises pharmacokinetics and pharmacodynamics of the oral anticoagulant drug, pharmacokinetics of the prothrombin complex and the relation between the activity of the prothrombin complex and the measured INR. It consists of two sub models in which the first sub model describes the collective influence of all processes on the effect of the vitamin K antagonist and the second sub model describes the relationship between the dosage and the corresponding INR. The second sub model includes a variable parameter to reflect the sensitivity of the patient that may change over time. In an expert evaluation 194 visits were randomly selected from the anticoagulation clinic database to assess whether the dosage proposal and appointment periods calculated by the algorithm were acceptable. In this evaluation the ICAD algorithm was able to give a good or acceptable proposal in 94.3%. The ICAD algorithm is described in detail elsewhere

Article is:
Towards Improvement of Oral Anticoagulant Therapy by Yvonne van Leeuwen and seems to be a PhD thesis.

 

[TheGymGuy]

I test weekly, and if I ever had to make adjustments you would never go up or down more than 5-10% of your total weekly doze to make adjustments and re-test. Simple scientific method.
Say you take 7mg per day @7 days per week (49mg per week) and your range is 2.0 - 3.0 and your weekly test came back 1.8-1.9. Assuming, you were pretty standard in your diet and activities, here is what you would do before re-measuring next week.

49*.5 (5% increase) = 2.45 or round up to 3mg. So by taking 1mg extra on Mon, Wed, Fri, you would effectively go up ~5%. Retesting a week later would show a difference. Though, if not enough, you repeat the same process. Also, the reverse would be done if your number was too high.

In addition there was a cool site where these were automated for you. There is a post in this sub-forum with it.

Hope this helps.

 

[UncleSteve]

Sorry, I was going to add the link, then..... So here it is http://anticoagulation-advisor.com/patient_version

 

[UncleSteve]

In addition there was a cool site where these were automated for you. There is a post in this sub-forum with it.

Do you have a link please?

Thanks

 

[pellicle]

Do you have a link please?

probably this one:
http://www.valvereplacement.org/forums/showthread.php?31691-Online-Coumadin-Dosing-Calculator

I found it by using google; enter the following in the search field, not the use of site:www.blah.com to restrict google searches to a specific site


site:www.valvereplacement.org dose calculator

 

[T in YVR]

Just FYI on another online software service - http://www.inronline.net/. Its a New Zealand company. This tool is endorsed by the Canadian College of Family Physicians and is apparently something they are talking about setting up in B.C. I'm not sure if individuals can just sign up and create an account - it did not look like this is possible yet. The software seems to be more directed at pharmacies, doctors etc, who then enroll their patients. The notion of setting up approved pharmacies with a CoaguChek unit to do the testing vs. the individual having to own the unit is also being looked at here. I think they're trying to eliminate the current system which is badly archaic - go to the lab, do a full blood draw and get your INR data/dosage from your doctor.

Once enrolled, you are given an account/login and can manage your INR (enter INR readings, and you get recommended dosages and next test dates, historical tables and graphs (like some of us use), a weekly email sent to you with your dosage calendar etc etc. Looks pretty cool actually.

Tony