Step II Antiphospholipid antibody syndrome. Why elevated PTT?

[mjmdjd1]

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In Antiphospholipid Antibody syndrome, we have autoantibodies(ie anticardiolipin or lupus anticoagulant) against proteins bound to phospholipids. And we know that for example, Lupus Anticoagulant, prevents coagulation since it's an anticoagulant. This would mean that it would increase the PTT aka bleeding(just how I think of it in my head).

Why do we then get arterial and venous thrombosis if the anticoagulant is present? and why do we then require lifelong anticoagulation(again, since anticoagulant is already present)?

I feel like I'm screwing up concepts here big time :-/

P.S. Be nice

 

[notbobtrustme]

it interferes with the test. it's procoagulating but the way the test is designed, the antibodies will interfere with reagents and cause a falsely elevated PTT.

 

[mjmdjd1]

Thank you very much