Development of Xa inhibitor activity in relation to postoperative deep vein thrombosis (DVT)

65 patients, undergoing hip or elective general surgery, were tested for Xa inhibitor activity using a differential assay. Classification into minor and major deep vein thrombosis (DVT) was made. This study indicates that patients with repeatedly decreased Xa inhibitor activity during the first two days after trauma are highly disposed to develop postoperative DVT. In 10 out of 14 major DVT this decreased Xa inhibitor activity was observed before any detection of DVT by objective tests was possible.