Lupus Anticoagulant
and thrombosis, monitoring of anticoagulation
Thrombotic complications are limb threatening and life threatening. There are multiple risk factors for
thrombosis in the arteries and veins. Lupus anticoagulant is one of the risk
factors for the development of thrombosis. Dr. Lockard Conley, haematologist
discovered the Lupus Anticoagulant in 1947. The two words in this term are misnomers.
This acts as an anticoagulant in the invitro and as procoagulant in vivo. It
was first discovered in Systemic Lupus Erythematosus patient, but not seen in
all patients with Lupus. Lupus anticoagulant (LA) is see in 2-4% of the general
population. Presence of LA increases the risk of thrombosis 3.6 folds. LA is positive in 10-30% of the SLE patients. Lupus
Anticoagulants are autoantibodies targeting phospholipids and proteins
associated with phospholipids on the outer cell membranes. Patients with some
infections or those taking certain medications can develop Lupus anticoagulants.
Nearly, 20% of the deep vein thrombosis patients with or without pulmonary
embolism are associated with antiphospholipid antibodies. The tests are done in
2 stages. At first PTT-LA, DRVVT are done. Then Anticardiolipin antibodies,
Beta-2 glycoprotein1 antibody, anti-prothrombin antibodies are tested to confirm
the antiphospholipid syndrome (APS) in patients.
It is important to give special attention
to the monitoring of warfarin therapy in APS patients. We are concerned about
the reliability of INR determinations in this group of patients with DVT/ PE. It
was observed that in 6.5% to 10% of patients with Lupus Anticoagulant, antiphospholipid
antibodies (aPLs) may prolong the prothrombin time assay leading to an
unreliable INR.1,2,3 It is helpful to validate the INR in
individual patients using a coagulation assay that is not affected by aPLs, suc
as Factor II activity assay.4 After an APS patient is on
warfarin with a stable INR of 2.0 to 3.0, an INR and factor II activity assay
should be checked simultaneously. If the INR is in range and the factor II
level is therapeutic (approximately 15% to 25%), the level of anticoagulation
in adequate and the INR is reliable. If the INR is in range but the factor II
level is >30%, the level of anticoagulation is inadequate. For such a
patient, an individualized INR target range corresponding to a therapeutic
factor II level should be established, or the factor II level itself could be
followed.4
1.
Moll S, Ortel TL.
Monitoring warfarin therapy in patients with lupus anticoagulants. Ann
Intern Med. 1997; 127: 177–185.
2.
Sanfelippo MJ, Sennet
J, McMahon EJ. Falsely elevated INRs in warfarin-treated patients with the lupus
anticoagulant. WMJ. 2000; 99: 62–64.
3.
Rosborough TK, Shepherd
MF. Unreliability of international normalized ratio for monitoring warfarin
therapy in patients with lupus anticoagulant. Pharmacotherapy. 2004; 24:
838–842.
4.
Kasthuri RS, Roubey RA.
Warfarin and the antiphospholipid syndrome: does one size fit all? Arthritis
Rheum. 2007; 57: 1346–1347.
