Unfractionated heparin (UFH) and low molecular weight heparins (LMWH) provide anticoagulation through their anti-Xa and anti-IIa activity. This anti-IIa activity can lead to an overestimation of argatroban's activity when switching to an anti-IIa anticoagulant such as argatroban. This situation can be critical because argatroban is generally administered following heparin therapy due to suspected heparin-induced thrombocytopenia. Therefore, there is both a significant thrombotic risk induced by the underlying condition and a hemorrhagic risk induced by the anticoagulation. For this reason, it is important to be able to accurately monitor the anti-IIa activity of argatroban. To date, the test used to determine the anti-IIa activity of argatroban at the Hematology Laboratory of the Strasbourg University Hospitals (HUS) is a modified thrombin time (with a calibration curve adapted for argatroban). When switching between several molecules with anti-IIa activity, this test does not allow for the differentiation of the anti-IIa activity attributable to each anticoagulant.

There are no data in the literature to determine whether heparins interfere with this test, and if so, its extent.

Inclusion Criterias:

• Adult patient (≥ 18 years)
• Patient anticoagulated with UFH or LMWH
• Sample sent to the Hematology Laboratory of the University Hospitals of Strasbourg (HUS) and analyzed for measurement of the anti-Xa activity of an anticoagulant in routine care

Exclusion Criteria:

• Patient receiving an anticoagulant other than UFH or LMWH
• Insufficient sample volume

Adult patient (≥ 18 years) anticoagulated with UFH or LMWH