Patients who present with LA are prone to thrombosis and may be treated with heparin. These patients will also have a prolonged baseline aPTT due to the nature of the LA. In order to determine appropriate clotting times, it is important to be able to neutralize the presence of heparin. If a sample is contaminated with heparin, it is possible to neutralize the heparin by adding heparinase. This enzyme degrades unfractionated and low molecular weight heparin by cleaving its pentasaccharide sequence at multiple sites. The most important is the antithrombin binding site which is required for heparin anticoagulation. This treatment can neutralize up to 2 units/mL of heparin.