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false positive Lupus Anticoagulant blood test

dwheeler profile image

I've read that if you are on Warfarin, then the lupus anticoagulant test can have a false positive result. Is that also true if you are on Pradaxa during the testing?

13 Replies

Hi dweeler,

I have no idea. Have not heard of Pradaxa and LA.

Best wishes from Kerstin in Stockholm

If you've already been diagnosed with APS (had the 2 +ve Tests 12 weeks apart) then you don't need another test. I'm on a different DOAC but haven't been tested since starting it. I don't know if they affect the Lupus Anticoagulant test outcome but someone else might be able to help you.

dwheeler profile image
dwheeler in reply to Ozchick

I am asking because after having dvt in lower calf and then 2 dvts behind knee a week later, I was put on Pradaxa. The didn't test my blood for lupus anticoagulant antibodies until about 4 weeks later, 1st test positive, and repeated 3 months later while still on Pradaxa, also positive. (the other blood tests for APS came back negative) At this time they switched me to Warfarin, saying that is better for testing and making sure blood is therapeutic. Dr. said she would test me again in 6 months, that one came back negative, and she said lets do it again in 6 months, that also came back negative. So now that leaves me wondering....

HollyHeski profile image
HollyHeskiAdministrator in reply to dwheeler

I'm really not sure why they keep testing you for LA?

Once you have a diagnoses its confirms you have APS.

Ive copied here an article response that Ive found regarding the test results 'testing for lupus anticoagulant among patients receiving anticoagulants "would appear to be unreliable," Although the Taipan/Ecarin ratio has been found to sensitive for the detection of these antibodies, "in our experience, false-positive results were seen with all types of lupus anticoagulant testing, suggesting that they cannot be used diagnostically for patients receiving NOACs,"

To be tested your blood needs to be at its normal state. This will show how sticky your blood is, and how quickly it clots. If you are taking warfarin or NOACs, your blood will not clot at the normal rate for your body, and so the test wouldn't give you an accurate result. Hope that makes sense!!

I would ask why they keep testing you?

Generally they do 3 tests when they first decide you have lupus anticoagulant ie: Antiphosphlipid syndrome or Hughes. You really need to see someone who properly understands this syndrome-and then be anti coagulated for life. The fact that you're still clotting would be a red flag for me. If the Pradaxa (Dabigatran) works for you then stay on it. Are you in UK or US ? -just so someone a bit closer than me can help you out with a suitable doctor.

If you can stay in a therapeutic range (and this is usually higher than the 2-3 that most doctors recommend) Warfarin is great for most people but with APS you will clot on the lower ranges. Some here have an INR of 3.8-4.0 to feel good.

Have you had the other tests: carddiolipin antibody and/or beata 2 glycoprotein? These 2 test results are not altered by blood thinner drugs. But they are diagnostic indicators of APLS.

I was told years ago that warfarin affects the "APS" test. When I recently saw a haematologist to confirm some APS things and make sure there wasn't anything else I could do, she said ALL anti-coagulent affect the L.A. testing, which is used as one indicator of APS and related conditions.

She also repeated that the fact that as I had suffered multiple thrombotic events while anti-coagulated, it made it largely irrelevant whether my APS/L.A. tests were positive, as I would need anti-coagulent for life based on my history.

They may be specifically testing you for it, because it would be undesirable to anti-coagulate you foe no reason. Were there any factors leading to the first DVTs? If they think there is a causal link to something else, them they could be trying to clear you of APS before giving a longer term anti-coagulent treatment.

The catch 22 is having to come off the (probably) essential anti-coagulent (for up to 6 weeks) to take a test to prove whether you need it or not. That's a risk I'm not prepared to take.

I've never read anything like that. My husband was diagnosed with APS & the lupus anticoagulant before he started taking warfarin.

I can tell you that the aCL and the Beta2-glycoprotein-1 (antibodies they test for APS) are not affected by Warfarin. How it is with the other oral anticoagulations I do not know.

If you are on Warfarin you may get a false answer on Lupus Anticoagulant.

You can get a diagnose of Antiphospholipidsyndrome on only one of the three antibodies if it is positive twice with 12 weeks between the bloodtests. You can also get a diagnose of 2 or 3 of the antibodies we test for APS.

After I started Warfarin they do not test me for LA anymore. I was positive a lot of times before I was anticoagulated with Warfarin. As i am triplepositive with very high titres since 2002 we guess that I am still LA positive even when on Warfarin.

Kerstin in Stockholm

Hello. I' am on baby Aspirin. Sorry!

Lure2 profile image
Lure2 in reply to luisal

Hi luisal,

How did the operation go? Did you have to stop Aspirin?

I know you live in Venezuela and not many Specialists there who had had patients like you before with APS but still I wonder if you have been lucky to find such a Doctor as I know APsnotFab told you to look for such a Specialist. I think she had found someone on our list, but not sure.

Many of us need an anticoagulation drug like Warfarin or LMW Heparin (Fragmin) to be safe from clots and other issues.

Do you have a Lupus Anticoagulant positive?

Best wishes and a Merry Christmas to you from Kerstin in Stockholm

I had to find a Dr that really knows about APS. First tests all positive, beta2, cardiolipin, Lupus Anticoagulant.They still didn't want to officially diagnose me. Hemotologist did,and found other clotting factors as well, never tested after Warfarin was started, other than regular INR checks. What can the do if your blood gets too thin on Pradaxa. Warfarin or Lovenox can be reversed in an emergency.

Lure2 profile image
Lure2 in reply to tchance11

Hi tchance11,

4 years ago you wrote that you were on Warfarin selftesting. Also later you wrote that you had got an appointment with Dr Brey in Texas. You were so happy and now you write that you are not yet officially diagnosed!!!!!

I get worried...... You should talk to Kelly here from Texas and hear what she thinks about this. Hope you read this now.....

A Merry Christmas to you in Texas from Kerstin in Stockholm! Stay with us please and tell us how it goes for you.

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