Positive results will reflex to additional testing.
Clot based assay
STACLOT confirmatory test: Phospholipid/Hexagonal Phase Phosphatidylethanolamine (HPE)
PTT-LA: ≤ 43.9 seconds
DRVVT ratio: < 1.20
Lupus anticoagulant testing results may be falsely positive in patients on anticoagulant therapy. We recommend disregarding results obtained while patient is on any form of anticoagulant. Consider consulting with Anticoagulant and Thrombophilia Clinic at 612-863-6800.
The diagnosis of antiphospholipid syndrome requires two positive Lupus anticoagulant test results, obtained at least 12 week apart, which have preferably been performed when the patient is off anticoagulation therapy. Testing for Cardiolipin antibodies (661) and Beta-2 glycoprotein 1 antibodies (7769) is strongly recommended.
Note that different PT/INR reagents available for use in labs have significant variability in their sensitivity to Lupus anticoagulants. In general, only 10-15% of Lupus anticoagulants affect the INR, leading to falsely elevated INR levels. Only in those limited cases would monitoring warfarin therapy by Chromogenic factor X (5767) levels be appropriate. Otherwise, PT/INR would still be the right test for monitoring patients with normal baseline INR.