This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Coagulation disorders, Subject name: Pediatrics
[{'content': 'The coagulation profile in a 13 year old girl with Menorrhagia having von Willebrands disease is: \nSelect and explain. \nA. Isolated prolonged aPTT with a normal PT, B. Isolated prolonged PT with a normal aPTT, C. Prolongation of both PT and aPTT, D. Prolongation of thrombin time', 'role': 'user'}, {'content': 'Answer: A \nExplanation: - Von Willebrand factor acts as a plasma carrier of factor VIII and circulates in blood as factor VIII-VWF complex. - Thus, VWF deficiency impairs intrinsic pathway of coagulation & prolongs aPTT - Extrinsic pathway of coagulation remains unimpaired, PT is not altered.', 'role': 'assistant'}]