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: Pathology
[{'content': 'A 23-year-old female presented with jaundice and pallor for 2 months. Her peripheral blood smear shows the presence of spherocytes. The most relevant investigation to arrive at a diagnosis is: \nSelect and explain. \nA. Tests for PNH, B. Osmotic fragility test, C. Coombs test, D. Reticulocyte count', 'role': 'user'}, {'content': 'Answer: C \nExplanation: The presence of spherocytes can be seen in the following conditions:\n\nHereditary spherocytosis\nAutoimmune hemlolytic anemia\nG6PD deficiency\nInfections\nBurns\nHemolytic disease of new born\nPNH is not a cause for the presence of spherocytes; so, no test for this condition is required.\nOsmotic fragility is increased with spherocytes. So, it does not add anything to our existing information about the disease causing spherocyte formation.\nReticulocyte count is expected to be elevated in the setting of haemolytic anemia (suggested by jaundice and pallor).\n\nCoombs test is done for detection of the antibodies formed against the normal antigens present on the surface of cells like platelets and red blood cells. So, it is going to be positive in autoimmune hemolytic anemia whereas negative in hereditary spherocytosis. Thus, a differentiation between these conditions can be done.', 'role': 'assistant'}]