Diagnosis of the prolonged activated partial thromboplastin time (aPTT)

Abstract

The aPTT is one of the most widely used global tests for blood coagulation. Indications for ordering aPTT include preoperative hemostasis screening, initial evaluation of hemorrhage and monitoring of heparin administration. The most common causes of aPTT prolongation are deficiencies or inhibitors of clotting factors. An unexpectedly prolonged aPTT is quite often connected with artifactual causes. In this paper we review the essential factors affecting aPTT results and provide a practical approach to the evaluation of a prolonged aPTT.