INR difference explanation?

[Marty]

The following was written by David Phillips of Hemosense to try to reassure patients who get different results from monitor and lab.

" Coagulation or INR testing is done to monitor the effect of the warfarin you are taking. The amount of warfarin you take is generally determined by starting with a dose and then taking a test to see what the INR value is. If it is too high, the doctor may reduce the dose or if it is too low he/she may reduce the dose. It is sort of a trial and error method but done cautiously. This is because warfarin is different from many other drugs because every patient metabolizes it differently. In other words, different people react differently to different amounts of the drug. This is because warfarin can be affected by diet, exercise, alcohol consumption, or other drugs taken. It is not unusual for a 115-pound woman to need more warfarin than a 200-pound man to stay in the 2.0-3.0 INR range.
What makes INR testing even harder to manage is that different testing systems give different results. This is because of many things but one of the main reasons is the sensitivity of the reagents used inthe testing systems are different because different manufacturers make them. The INR was developed to address these differeances but it doesn't eliminate them all.
Let's use an example. Let's say the two people are in a large room and need to know how long the room is but neither has a ruler. One is 5'2" tall and the other is 6'3". The short person measures it at 21 steps and the tall one says it is 16 steps.Which one is right? Well, both. The room is the size it is.
Different labs have different measurement systems. Some are more sensitive than others (taller?).They get different numbers.
The best solution is to use the same system all the time and not compare one to the other.As long as you "step it off" the same each time you will be able to determine any changes in your INR and those changes would be based on that system only.
Confucious say , Man with one watch knows what time it is, man with two watches never sure."
So as you move to your new self testing system, use it to determine changes from the last INR or how you are trending. Note how the results might be related to change in diet, medication, or activity level.
Self-testing will give you the ability to test more frequntly so you can evaluate what affects you and the dose of warfarin you need to stay in the prescribed therapeutic range. Your doctor and you can work as a team. The doctor will appreciate what you are doing to help yourself and him/her."

David would appreciate feedback from vr.com Would a note like this have helped you self testers when starting out?

 

[geebee]

It helps some but does not really address one issue. If you have been testing at a lab for years and say you test consistantly at 2.7. Then you get an INRatio and test consistantly at 3.4. Both in range so you might say no big deal. However, if you drop to 2.7 on the INRatio, you might end up under range on the lab test. What do you believe? That you are still in range or you need to up the coumadin?

OR do you just make sure you keep things on the high side testing on the INRatio and forget about the lab test results?

If I am not making sense, I apologize but............

 

[Guest]

I have run hundreds of QA checks on meters and if you are testing five meters you will often get 2.0, 2.1, 1.9, 3.6, 2.0. Then you test the next person's blood and get 2.0, 2.0, 2.1, 2.0, 2.0. If you test a third person you might get 3.6 3.1, 3.4, 3.0 and 4.0.

The point is that the meter that gives a higher or low number is random. If you send the person to the lab then you have the problem with the two watches.

So, my philosophy is don't get more than 0.2 units below the desired range and don't get above 5.0.

I've done over 30,000 tests and my complication rates are
minor bleeding - 1 for every 1.5 patient years
major bleeding - 1 for every 33 patient years
clotting - 1 for every 100 patient years

This is for all diagnoses not just valves.

My guess is that you could test every week and get your time in range up around 90% but it would not get the major bleeds down to 1 in every 35 patient years nor the clotting down to 1 in every 110 patient years.

What would help more than accurate meters is to get people to stop doing stupid things. Two examples from the last two days.

One guy's wife took him to a naturopathic physician to have his heart healed. His INR two weeks ago was 1.0. I asked his wife to bring in the supplements that he started. There were over 100 ingredients. When I untangled the web he was getting 2 mg of vitamin K every day for the past two weeks. 2 mg is probably enough to reverse an INR of 10 in 24 hours. He was taking this much every day!!! Two weeks later his INR is still 1.2 despite tripling his warfarin dose because the vitamin K is fat soluble and it hangs around for weeks maybe months in his case. I said I don't know about healing the heart but he will be lucky if he gets out of this being able to move his arms and legs if he has a stroke.

The other one has a relative who is a neurosurgeon. Of course he sees the worst warfarin disasters. He gave some advice about getting a tissue valve so he wouldn't have to take rat poison. Well two weeks post-op the guy has atrial fibrillation so his wife decided that he needed a magic diet. This involved massive intake of Lactobacillus bacteria - the guys that make vitamin K. Well his INR dropped to 1.1. So in spite of the fact that he wanted to avoid rat poison, he now needs massive doses of it.

So I'm not sure that we need better meters. I think we need smarter people.

The amount of intelligence in the world seems to be constant but the population is increasing.

 

[jeffp]

The amount of intelligence in the world seems to be constant but the population is increasing.

Do you mind if I steal this quote? I see so many times each day it would be appropriate.

 

[Guest]

You can't steal it from me - I'm already guilty of receiving stolen quotes. I probably heard it about 20 years ago and just remembered it yesterday.

 

[Marty]

Geebee, Your comment was not only relevant but is the crucial question. How close is close enough? Al's encyclopedic knowledge I believe can help us.
The variation in INR with different labs, meters, diets, etc., I believe , make it mandatory that each individual patient be consistent in life style and test only one way-central lab, Protime, Coaguchek, or INRatio.The Oracle at Delphi cautioned pilgrims to KNOW YOURSELF! NOTHING IN EXCESS! and that includes overtesting with various methods. Even though trained in medicine I started out thinking this was rocket science and was upset when the readings on the meters and the central labs weren't within .001. Now that I have learned differently I hope tp pass on some of this experience to others just beginning the long warfarin journey.