Q: To avoid falsely low Anti-XA assay for Heparin/LMWH anticoagulation effect, what is the most optimum time in lab to separate plasma from cellular components?


Answer: To avoid falsely low Anti-XA assay for Heparin/LMWH anticoagulation effect, Plasma must be separated from cellular components within 1 hour. Platelet factor 4, released by platelets, neutralizes the effect of heparin.



Reference:

Weitz JI. Antithrombotic Drugs. In: Hoffman F, Benz EJ, Shattil SJ, eds. Hematology: Basic Principles and Practice. 5th ed. Philadelpha, PA: Churchill Livingstone; 2009: Chapter 137.