The full log:
https://docs.google.com/spreadsheet/ccc?key=0AuMPbkwYwfZpdDkxUXo2NHltU2JSdGxWQUU1blFzNXc&usp=sharing
A summary of some of the premises for this test and some of the questions that were asked:
- I have a CoaguChek XS, and I check it against the lab every time I am there. It has always been +-0.1 or 0.2 of the lab result. The lab is a proper lab in a hospital, doing a full blood draw (they do not just use another CoaguChek as far as I know). This indicates that the CoaguChek is pretty accurate. Anyway - this experiment is mostly about the variation of INR, not the actual value, and the variation will probably be big enough to show even if the meter is not 100% equal to the lab results.
- I know some of the changes will take a few days to show up in my INR, so my plan is to change my diet/habits on a Monday, and keep it that way for at least two or three days, and then fall back to "normal".
The idea is that I should then see a spike - either up or down, depending on the change - in the middle of the week, and then slowly getting back to my baseline during the weekend.
- And I also am aware that INR will change anyway. But a just as important result for me would be if I see that sharing a bottle of red wine, or having a few beers a couple of days in a row will not affect my INR more than the normal variance.
- Whatever results or conclusions I draw might or might not apply to others. We are all different, and might react differently to IE alcohol, various vegetables with different amount of vit. K, depending on your regular diet and so on. So these results are by no means universally applicable. If in doubt, do your own test.
- I use a few arbitrary measurements for "Alcohol", "Greens" and "Exercise" in my original google-spreadsheet:
For alcohol, I simply count any "drink" as a +1. So a beer is a +1, a glass of wine is a +1 and so on no, matter the size or alcohol%.
For greens, I use a kind of scale from 0 to 5, where I can give 1 point for breakfast, 2 for lunch and 2 for dinner. 5 means that all meals are mostly based on green vegetables. 2 can imply that most of the dinner was vegetables, or that around half the lunch and half the dinner was green leaves. and so on.
Exercise also is a scale from 0 to 5, where 5 is what I personally consider a maximum possible workout in a day. 2 is then a moderate workout and 4 is an intensive, but not completely exhausting workout.
In the graphs below, I simply indicate which days I changed from my regular habits. Not how big the deviation was.
Background
I dose my Warfarin on a weekly basis, and have kept my dosage constant during the whole experiment. As I am a bit lazy, I don't bother dividing the small pills, so I do not take the exact same dosage every day. I use 2.5 mg tablets, and vary between 3 and 4 during the week, following this scheme:
Mon | Tue | Wed | Thu | Fri | Sat | Sun | = |
10 mg | 7.5 mg | 7.5 mg | 7.5 mg | 10 mg | 7.5 mg | 7.5 mg | 57.5 mg |
Since a dose of Warfarin lasts for 2-5 days, with a half time of about 40 hours (
http://en.wikipedia.org/wiki/Warfarin) this means that if all other factors were the same, my INR-level would in theory vary between 2.6 and 3.0 according to the following graph:
Of course not all other factors are the same (especially during this experiment, which sole purpose was to test how different external factors will influence the INR-level), but if we add the real INR-levels I measured during the experiment to this graph, there is quite a nice correlation:
There are a few noticeable exceptions, which I will comment on further down. It is worth noting that graphs like these will never follow each other 100%, as I only measure my INR once a day, and the time of day might vary a bit, and also this measurement is a snapshot of that particular time, not an average for that day. So the graph might show a falling line, whereas the INR might in reality be on the way up already because the bottom was reached a few hours before the actual measurement was done.
Now, back to the deviations.
Week one - 2013-11-04 - 2013-11-10
The first week, I wanted to test how much effect alcohol would have on my INR level. The theory was that alcohol would elevate the level, and that it would be a statistically significant variation from the theory-graph. As you can see from the graph above, I started out pretty low, with a 2.4 and 2.3 the first two days. I believe the reason for this is that I had quite a bit of green vegetables the days before (2013-10-31 and 2013-11-01). This explains why the INR-line (blue) is quite a bit lower than the theory (red) - and going down - between 2013-11-01 and 2013-11-02. On 2013-11-03 the level is growing, and staying "high" until 2013-11-07.
Below, you can see the same graph, but with added yellow "dots" for the days I drank alcohol. It seems from this graph, as the effect of alcohol for the first days of November was pretty moderate, but the INR level is staying higher than it should according to theory for at least two days. A really interesting effect happens at the end of the experiment, where I see a much greater effect, with a huge spike in the graph.
The amount of alcohol I drank on this single day (2013-11-21) was not greater than some of the other days, but it still shows a really significant rise in the INR-level. But I did drink more beer and less wine. So this might suggest that it is not necessarily the alcohol itself that is the culprit, but it might be something else that is present in beer, but not in the (white) wines I drank more of early in the experiments. @Protimenow has suggested this as well, as he observes that some red wines will effect his INR level more than other alcoholic beverages. There are several interesting (and possibly quite funny) experiments one could follow up with here.
- Try to drink a lot of no alcoholic beer, and see if that makes a difference.
- Drink only red wine, or only white wine for a few days and check the INR daily.
- Drink vodka (or some other "pure" alcohol) to avoid other chemicals interfering with the results
I will save this for later.
Week two - 2013-11-11 - 2013-11-17
This week was about vegetables - or more specifically green vegetables. I did not use a vitamin-k-list to plan my meals, as it is a quite established fact that vit. k will lower your INR. I did however eat
more of the vegetables I like, and hence is more likely to eat more of in a normal situation as well. The reason was to see how much a diet I could probably live on for a few days would effect my INR, not to see what would happen if I only ate broccoli or spinach for a week.
Here is the same graph, but with green dots for the "extra vegetables"-days.
It seems like vegs has a pretty much instant effect. It will lower the INR, but with my doses, not to a dangerous level. I should probably be a bit careful if I change my diet to a more or less vegetarian only, but with what I would consider a normal amount of green leaves a few days in a row, the INR did not go below 2.3, and quickly recovered to a normal level as my diet changed back.
Week three - 2013-11-17 - 2013-11-24
The last expermient was supposed to look at exercise. I was not sure what to expect, but I thought that heavy exercise would in some way affect the INR. Either make it higher or lower. The graphs do not show anything that suggest either. If anything, they
might suggest that the INR is kept more stable, but I do not think this is statistically significant, and is probably caused by other kind of "background noise".
So the most interesting thing to read from the graphs during this last week was that one heavy night out might lead to quite a big spike in your INR, but it will go back to normal in just a couple of days.
Conclusions
These conclusion are NOT universally applicable. These are only my thoughts after doing one single experiment for less than one month on MY body, living MY life. However there are a few nice things that at least makes me feel more confident when I self administer my warfarin dosage.
- My body recovers quickly, and will get back to a normal level after only 2-3 days, even after a huge spike such as the one on 2013-11-22. Already one day later, I can probably see which direction my INR is going. If I measure an INR-level I feel uncomfortable with when I do my normal, weekly check, I can do another test the next day, and be confident that if the level is about to normalize after this second test, everything is probably fine. If I see an "extreme" result (> 3.5 or < 2.0) more than two days in a row, I will adjust my dosage slightly and do another test a day or two later.
- However, these rapid changes also shows that it is not unthinkable to have huge variations in your INR in just a short time, and that even weekly testing might not pick this up. I still do not think testing more often than weekly should be necessary, as these spikes or drops will be of a short duration, but it also shows that only testing monthly could lead to prolonged periods of being out of range if external circumstances changes.
My biggest changes from one day to another was +0.8 (2013-11-21 - 2013-11-22) and -0.7 (2013-11-23 - 2013-11-24), but it was not uncommon to go +/- 0.3 from day to day.
- The vegetables I would normally eat cause only a slightly lowered INR. There is no reason for me not to eat a salad, a broccoli puree or a portion of steamed peas with a grilled steak a couple of days a week. Unless I change my diet dramatically, to a more or less vegetarian only, I should not be concerned at all, even if my INR is < 2.5 on a Sunday after having a great Saturday dinner with a lot of vegetables.
- Alcohol is an interesting thing to watch out for. But unless I drink excessive amounts of beer, probably several days in a row, it should not be anything to worry about (INR-wise). After a heavy night out on Thursday, I had a huge spike in the graph with INR reaching as high as 3.8 on Saturday. But already on Sunday the INR was back down to 3.1 and Monday I measured 2.7.
All in all, I feel that this test has proven that self administration is not difficult. As soon as you have found your right dosage, your body will quickly readjust and get back to a normal INR in just a couple of days even if you go crazy with drinking or eating for a day or two. So don't worry about that upcoming holiday season or the anniversary you want to celebrate. Enjoy your life!
But we
have seen examples where you might have to adjust your dose, even after having found a "stable" regime:
http://www.valvereplacement.org/forums/showthread.php?42132-NovembINR&p=545404#post545404
So if your INR is higher or lower than normal for more than a few weeks, you might want to change the dosage slightly. After doing that, you would want to keep a closer eye on it for a while to be sure you do not over compensate.
Anyway, the effect of both a changed dose or variations in your diet will be pretty instant, and if you do not see anything after 2-3 days, it probably did not have an effect. But that also means you will have to be careful not to make changes based on a single measurement. A few extra pieces of broccoli on Thursday might show up on your Saturday INR-test, but will be totally gone by Sunday. If you are uncertain, try to do tests on different weekdays, as regular habits might influence your INR in such a way that Monday is always lower than average, or Wednesday is always in the high end. Instead of testing weekly on the same day every week, maybe try to test every 6 days for a few months, just to check.