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: Orthopaedics
[{'content': 'A lady presents with right knee swelling. Aspiration was done in which CPPD crystals were obtained. Next best investigation is - \nSelect and explain. \nA. ANA, B. RF, C. CPK, D. TSH', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Finding CPPD crystal in aspirated synovial fluid is diagnostic of CPPD arthropathy.\nCPPD arthropathy in some patients may be associated with :- Primary hyperparathyroidism, Hypothyroidism, Hemochromatosis, Hypomagnesemia, Hypophosphatasia.\nANA (antinuclear antibody) is for SLE, RF (rheumatoid factor) is for rheumatoid arthritis and CPK (creatinine phosphokinase) is raised in dermatomyositis & polymyositis.\nSo, among the given option only TSH is the relevant investigation in context of CPPD arthropathy as it may be associated with hypothyroidism.', 'role': 'assistant'}]