Dear George, I have a lupus anticoagulant (LA) positive patient with recurrent pregnancy loss. She is on low molecular weight heparin (LMWH) with a request for an anti-Xa assay. Will LA positive whether it is interference by LMWH? What is your opinion? Hello, Vilas, the chromogenic anti-Xa heparin assay provides an accurate measure of unfractionated […]

From Pam Owens at TriCore Reference Laboratories in Albuquerque: We are wondering if other labs research their patients’ positive antiphospholipid antibodies (APA) such as the lupus-like inhibitor (LLI, lupus anticoagulant, LA), anti-cardiolipin antibody (ACL) and β-2-glycoprotein 1 (β2GP1)) results to differentiate between persistent and new diagnoses. If so, how far back do they look for a positive? For example, if […]

From someone at Lancaster General: I was wondering whether you could help me with a problem that I have not been able to resolve with certainty. It relates to how long does a patient need to be off warfarin or heparin before lupus anticoagulant testing can be done. I have seen different recommendations ranging from […]

In reviewing an article by Dave McGlasson, Wilford Hall USAF Medical Center, San Antonio, that compares several dilute Russell viper venom (DRVVT) kits for their accuracy in detecting lupus anticoagulant, I noticed that Dave advocates for DRVVT ratio normalization, using the attached formula. I may be behind the times, but this is a new concept to […]

From “Sunny,” What is the reason for not using prothrombin time (PT) in investigating lupus anticoagulant (LA)? It is also a phospholipid-dependent assay. Thanks. Hello, and thank you for your question. Although a particularly avid LA may on occasion prolong the PT, PT reagent (thromboplastin) phospholipid is typically concentrated enough to neutralize plasma LA so […]