This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pediatrics
[{'content': "The coagulation profile in a 13–year old girl with Menorrhagia having von Willebrand's disease is – \nSelect and explain. \nA. Isolated prolonged PTT with a nonnal PT, B. Isolated prolonged PT with a normal PTT, C. Prolongation of both PT and PTT, D. Prolongation of thrombin time", 'role': 'user'}, {'content': "Answer: A \nExplanation: Von Willebrand's factor acts as a plasma carrier of factor VIII and circulates in the blood as factor VIII-VWF complex. Its deficiency, therefore, impairs the intrinsic pathway of coagulation and prolongs the PTT as the intrinsic pathway of coagulation remains unimpaired, PT is not altered.\n\ni)\xa0Bleeding time\n\nIt is a not a test for coagulation rather it tests the ability of the vessels to vasoconstrict and the platelets to form a hemostatic plug.\nIt is the time taken for a standardized skin puncture to stop bleeding.\nNormal reference value is between 2-9 minutes.\nProlongation generally indicates the defect in platelet number or function.\n\nii) Prothrombin time (PT) \n\nThis assay tests the extrinsic and common coagulation pathway.\nSo, a prolonged PT can result from a deficiency of factor V, VII, X, prothrombin or fibrinogen.\n\niii) Partial thromboplastin time (PTT) \n\nThis assay tests the intrinsic and common coagulation pathways.\nSo, a prolonged PTT. Can results from the deficiency of factor V, VIII, IX, X, XI, XII, prothrombin or fibrinogen.\n\niv) Thrombin time\n\nIt is the time taken for clotting to occur when thrombin is added to the plasma.\nIt tests the conversion of fibrinogen to fibrin and depends on adequate fibrinogen level.\nProlonged thrombin time results from a decreased level of fibrinogen.", 'role': 'assistant'}]