A deficiency in which of the following blood coagulation factors could most likely be suspected in a patient exhibiting a prolonged aPTT time?

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Quizplus · Accepted Answer

Factor IX deficiency, also known as Hemophilia B, leads to a prolonged activated partial thromboplastin time (aPTT) because it is part of the intrinsic pathway of the coagulation cascade.  The partial thromboplastin time (PTT) is used to assay for defects in the intrinsic pathway of coagulation. The PTT assay has been modified by the addition of activators that shorten the normal clotting time and this form of the assay is referred to as the activated partial thromboplastin time (aPTT). The assay will evaluate the function of fibrinogen, prothrombin, and factors V, VIII, IX, X, XI, and XII. A defect in any of these factors will result in a prolonged PTT (or aPTT).

A Deficiency in Which of the Following Blood Coagulation Factors