D) PFA-100 is correct.
 

Key Concept/Objective: To understand the uses of different coagulation tests.

This patient has a prolonged bleeding time and a history of a previous bleeding episode. She also has a family history of a mild bleeding disorder. Von Willebrand disease is the most likely etiology. The testing of bleeding time primarily measures platelet function. A prolonged bleeding time with a platelet count over 100,000/ml suggests impaired platelet function. The bleeding time is difficult to standardize, and a normal bleeding time does not predict the safety of a surgical procedure. Bleeding time should not be used as a general screening test in a preoperative setting. Although once used commonly for screening of platelet disorders, bleeding time has been replaced by the PFA-100. PFA-100 is a newly developed automated test of platelet function. Citrated blood from the patient is aspirated onto a membrane coated with collagen and epinephrine or collagen and ADP in which a central aperture is made. The time it takes for blood flow through the membrane to stop is denoted as the closure time and is a measure of platelet function. The closure time is prolonged in patients with von Willebrand disease or other platelet functional defects. PFA-100 should be considered the first-line test for platelet function disorders. Thrombin time is used to test for abnormalities of the conversion of fibrinogen to fibrin. Thrombin time is prolonged in patients with severe liver disease and DIC and those undergoing heparin therapy. Factor VII levels are measured in patients who have a prolonged PT; it is a test of the extrinsic system. Factor XIII is the only clotting factor whose activity is not assessed in PT or PTT; a deficiency should be suspected in an infant who experiences bleeding after circumcision or in an adult with unexplained bleeding.