A Lupus patient clots
Patient I.A..- 49 y/o wf with SLE x 14 years S/P aorto-femoral bypass 3 weeks ago presents with postural hypotension. Dopplers of legs negative but Spiral CT shows saddle-distribution embolus. History of DVT 6 years ago after left THR.
What tests should be drawn? Ultimately what should target INR be? How long should she be on Coumadin?
Naturally with her history of lupus, a work-up for Anti-Phospholipid Antibody Syndrome (APAS) is first and foremost-Lupus anti-coagulant screen and IgG and IgM anti-cardiolipins (ACLA) were negative, as was the seemingly more sensitive IgA ACLA and anti-beta-glycoprotein I. A RAPC assay, PCR for PT 20,210, Protein C,S and ATIII levels were all negative- they were ordered because of history of clotting at age < 45.
The target INR is historically 3.0-4.0 in APAS patients but we advocate 3.0-3.5 and then check a chromogenic Factor X assay and raise the Coumadin dose to INR of 4.0 if the FX level is still > 30%. If the hypercoaguable work-up is completely negative, one could argue for just 6-12 months of Coumadin given presumed risk factor of recent surgery as was the case 6 years ago with the first DVT though her recent arterial clot is suspicious for APAS but on the otherhand she is also a diabetic and hypertensive at risk for arterial disease.
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