From **** Clinic Hematologist:
I had a detailed discussion with patient regarding the lupus anticoagulant testing, and I have explained to him that to call a person to have a positive lupus anticoagulant, the phospholipid-dependent clotting time (either APTT or DRVVT) should be prolonged, and it should be inhibited on equal volume mix testing with pooled normal plasma.
Furthermore, the clotting time should shorten by addition of excess phospholipids, thus demonstrating the phospholipid dependence. Warfarin anticoagulation can lead to false-positive lupus anticoagulant testing, especially with the DRVVT method. However, in patient's case, his lupus inhibitor screen (both by APTT and DRVVT) have been negative in October 2016, early January 2017, and late January 2017.
Again, I emphasized that warfarin can lead to false-positive test, but not false-negative tests. To call individuals with a thrombotic event to have antiphospholipid antibody syndrome, they need to have persistently positive lupus anticoagulant, anticardiolipin antibodies (either IgG or IgM), or anti-beta-2 glycoprotein antibodies (IgG or IgM) when measured at least three months apart. In patient's case, he had a single positive lupus anticoagulant test (July 2016), and his subsequent three tests have been negative. Thus, he does not meet the laboratory diagnostic criteria for antiphospholipid antibody syndrome.
****Edited by Admin**** As per our Guidelines