F10 and hereditary antithrombin deficiency: In this situation of antithrombin deficiency, our anti-FXa test, nevertheless, reflects a value that really corresponds to the patient’s UFH effect on factor X. Therefore, a discrepancy between the anti-FXa value and the dose of UFH administered will indicate the need for possible antithrombin supplementation, as opposed to a test corrected for antithrombin which would be falsely reassuring.