Anti-Xa Assay With LA Present?

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 heparin, LMWH, and synthetic pentasaccharides (fondaparinux) in the present of lupus anticoagulant. There exists a clot-based anti-Xa heparin assay, this would be affected. Geo.