Soru

A 32-year-old woman is evaluated in the preoperative clinic prior to an elective laparoscopic cholecystectomy. She has no significant past medical history and takes no medications. She reports normal menstrual periods and denies any history of easy bruising, epistaxis, or prolonged bleeding after minor cuts or prior dental extractions. Routine preoperative laboratory testing reveals a normal prothrombin time (PT) of 11.5 seconds and an isolated, significantly prolonged activated partial thromboplastin time (aPTT) of 62 seconds (reference range: 25-35 seconds). Her platelet count is $210,000/\mu L$.

Arrange the following laboratory tests in the most appropriate sequential order to establish the etiology of this patient's isolated prolonged aPTT, from the initial evaluation step to the final diagnostic confirmation.