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': 'Ham test is done for - \nSelect and explain. \nA. PNH, B. Megaloblastic anemia, C. Sickle cell anemia, D. Thalassemia', 'role': 'user'}, {'content': "Answer: A \nExplanation: Diagnosis of paroxysmal nocturnal hemoglobinuria\n\nUntil recently the diagnosis of P.N.H was based on special tests that were based on the principle that P.N.H red cells are susceptible to complement-mediated lysis. These tests are :\n\nHAM Test\n\nHam's acidified serum test is one of the screening tests for P.N.H. Patient's red cells gets lysed in an acidic pH in the presence of complement.\n\nSucrose Test\n\nRed cells lyse on the addition of sucrose and complement in the medium.\nAddition of sucrose decreases the ionic strength.\nBut now the diagnosis of P.N.H depends upon analyzing the expression G.P.I—AP on the hematopoietic stem cells using monoclonal antibodies and flow cytometry. The simplest method is to analyze the expression of CD59 on erythrocytes.\nPNH is diagnosed by flow cytometry, which provides a sensitive means for detecting red cells that are deficient in GPI-linked protein such as CD59.", 'role': 'assistant'}]