Hello Everyone!!

Hope all are well!! I have a question, I was going through some posts & there was a discussion about INR levels. Difference between a finger prick & vein tests for protine. My Dr likes to keep mine 2.2-3.2 I have suggested it Be he higher, but not happening with them. Can someone explain does the Vein give a higher or lower reading than the finger??? And why? Thanks!!!

10 Replies

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  • If the testing equipment is fully calabrated then both should give a correct reading.

    On saying this I have had 2 differant hospitals give me a .2 differance every time. My usual local hospital has always been .2 higher than the heart Hospital I have attended.

    In the UK samples of the same blood are sent test samples which should always give the same reading? so strange that they give me a differant reading? This has been over a 12 year period?

    Be Well

  • The APS antibodies can affect the tests, particularly if you are LA (lupus anticoagulant) positive. Typically LA+ patients have a _higher_ INR reading from finger prick testing, the venous test is always regarded as more accurate, not sure exactly why - there is more blood to test but also the labs use different reagents to the test strips. Lupus Anticoagulant is actually tested for by looking for increased PT time in vitro - the blood actually takes longer to clot in the lab, but makes more clots in the body - this is also why once you are on warfarin you can no longer have LA test.

  • Hi, I can not explain this in detail as English is not my language but I can say that the vein-test at the hospital is always lower than the fingerprick test on my CoaguChek XS-machine. Usually around 0,8 but if the INR is near 6.0 (fingerprick) it could even be more.

    My Hematologist says it is the vein-test at the hospital that counts. So I always lower my selftest-result to know what the REAL value on my INR is that special day.

    I selftest since 5 years back every second day and make notes if I do changes or if something special happens (illnesses, ny drugs, other food etc etc). I have followed my values back and can see that the DIFFERENCES between the two is almost exactly the same.

    I am however Lupus Anticoagulant and triple-positive with high titres also. The LA-antibody can make it difficult to selftest. I did doubletests for half-a-year when I started selftesting to make sure that the DIFFERENCE BETWEEN THE TWO was always the same.

    Nowadays i doubletest at the hospital every three months. The tests are taken within a couple of hours.

    I do not know how others are - higher or lower veintest than fingerpricktest!! I only speak of myself. I only know that the Lupus Anticoagulant-antibody can give false testresults. I trust my CoaguChek XS and we have made doubletest with other machines also. It is usual that it differ 0,2 and also when I take a new test-box of 24 strips.

    It is of course very important to know this otherwise you do not know "where you are" at all. I find it curious that the Doctors do not know about this but probably it is because they are not Specialized on APS.

    A very good question and I will read the answers with great interest!

    Best wishes from Kerstin in Stockholm

  • I am positive for lupus anticoagulant and my finger prick test with my coaguchek is always higher. My haematologist says it's something in the antibodies that reacts with the reagent in the test strip that gives a false high positive - but not for everyone. The difference varies between 0.7 and 1.1. So today my coaguchek says 5.4 so I know I am actually 4.3-4.7 - to high by a little. My new target is 4. I'll just eat a little extra broccoli and be in range tomorrow.

    This does not happen to everyone and this is why dual testing with vein and finger is needed.

  • Vein draw today was 4.5 so it was where I expected it to be.

  • In some people there can be a slight variation between home and the clinic, so, that is why it is important to have some testing still going on at the hospital, so that the over view can be taken. Testing at home is not for everybody but the majority find it more than useful. I have never done this, having not been on Warfarin, I am sure however that APsnotFab will give you a more detailed response than mine, as she was once on long term Warfarin. MaryF

  • I don't think I can add much from everyone else who I agree with. Those who are LA positive as I was do tend to have a little more difficulty with it and sometimes it can be difficult to keep a stable INR, as it was with me. I was never given the opportunity to self test as my health authority would not allow it but even if I was in the end I was allergic to the warfarin so had to stop. The gold standard is to have a vein test at least every 6 months if you are not self testing and just having finger testing and if you are you should have your machine calibrated at least once a year.

    In answer to your specific question GirlfromTennessee Prof Hughes always says that INR should be at least 3, he compares it to having your blood like semiskilled milk instead of cream. What INR you do have will depend on your clinical situation, if you have had a clot or not and what symptoms you have. Normally a person who has had an arterial clot will need a higher INR that a person who has had a venous clot but then if a person has no symptoms they may manage on a lower INR. The aim is to have the lowest INR managing symptoms and only raise it if symptoms persist. It would be like treating a diabetic person on too little insulin in that situation.

    The vein will always give a more accurate test result than a finger prick test because of the chemicals used on the test strips but the difference should only vary by up to 0.6 at the most depending on your machine and which antibodies you are positive to.

  • Thank You so much!!!

  • How did you notice that you were allergic to the Warfarin?

    Kerstin

  • I had a very itchy red rash which looked a bit like flea bites! prof Hughes said stop so I did ..... not one to argue with him!

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