The Anonymous Widower

Conclusions From Self Testing My INR Daily

Tomorrow, it will be eleven weeks since I started self testing my INR on a daily basis. The results are here.

I should say that after I had my stroke, an eminent cardiologist said that if I got my Warfarin right, I wouldn’t have another stroke.

So can I come to any conclusions from the tests I have been taking?

I did miss one day early on, but otherwise I’ve taken the test successfully on a daily basis.

I’ve now developed a daily routine in the morning, where I do my stretching and exercises after checking my computer, then have a shower and breakfast, before doing the washing-up by hand, which warms my hands.  I then take the test and only rarely do I fail first time and need a second strip.

So the first conclusion, is develop a routine for when you do your tests, that suits your personality and lifestyle.

One thing that you notice from the tests, is that there is quite a large variation between days.  A change of 0.5 in the INR, either up or down is not uncommon. This is not a problem, but it could with some people worry them and then they might start to chase their target INR, by constantly changing the dose.

Hot days incidentally, do seem to try to force the INR upwards and although you won’t find this on the Internet, a medical professional has told me that it happens.

I use a very simple manual algorithm, based on my training and experience as a Control Engineer. I know from when I was living in Suffolk, that a Warfarin level of 4 mg. a day is about right to meet my target of 2.5.  So I use a simple algorithm, summarised as follows.

INR less than or equal to 2.2, take 5 mg.

INR higher than or equal to 2.8, take 3 mg.

INR between 2.2 and 2,8, take 4 mg.

So how has my INR behaved?

If I look at the average value of the last 28 days, it is 2.56 and this rolling 28 day average has been within 0.1 of 2.5 for the last seven weeks. I couldn’t calculate it before, as I didn’t have enough data. An interesting figure is that the standard deviation of the readings is about 0.3. Effectively this says that nearly all of the readings are within 2.2 and 2.8, which is within my target range of between 2 and 3.

So as the patient, I think I could safely say that my simple algorithm works.

But perhaps what is most interesting is that the 28 day average for the dose I’m taking is around 3.8 mg. So rounding this to the nearest tablets, that means if I can’t take a reading for some reason, then I should take 4 mg.

So I can conclude that the daily testing has given me a very sensible daily dose, which is virtually the same, as I took, when the tests were done by nurses, hospitals and laboratories, at great expense to the NHS.

So should all those going on Warfarin be assessed to see, if they could self-test their INR levels?

I believe they should!  And it’s not just me!

An organisation called the Anticoagulation Self-Monitoring Alliance is pushing for more self testing. Be cynical if you like, but it is part-funded by Roche, who make the self testing meters.

On the other hand, how many diabetics test their blood sugar levels regularly and have a better lifestyle because of it?


August 2, 2013 - Posted by | Health | , ,

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