Coagulation Disorders

Which laboratory finding best distinguishes Disseminated Intravascular Coagulation (DIC) from Vitamin K deficiency in a patient with both prolonged PT and aPTT?

A 35-year-old woman with a lifelong history of easy bruising and menorrhagia is found to have a prolonged aPTT, normal PT, and normal platelet count. Mixing study corrects the aPTT. Which finding best distinguishes Factor V deficiency from Factor VIII deficiency?

A 28-year-old man with no prior bleeding history presents with acute onset of severe thrombocytopenia (platelets 8,000/μL), microangiopathic hemolytic anemia (schistocytes on blood smear), acute kidney injury, fever, and neurological symptoms. Which investigation is most specific for confirming the diagnosis of thrombotic thrombocytopenic purpura (TTP)?

A 35-year-old woman presents with a 2-year history of recurrent spontaneous bruising, epistaxis, and menorrhagia. Platelet count is 45,000/μL. Bone marrow examination shows adequate megakaryocytes. Which investigation is most appropriate to confirm the suspected diagnosis of immune thrombocytopenia?

A 32-year-old woman presents with recurrent thrombosis in the deep veins of the lower limb. Investigations reveal activated protein C resistance and genetic testing confirms Factor V Leiden mutation. She is not currently pregnant. What is the drug of choice for long-term anticoagulation in this patient?