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': 'Deficiency of Vit. C in infant is best estimated by Vit. C level in – \nSelect and explain. \nA. Plasma, B. Urinary excretion, C. Buffy coat estimation, D. Adrenal cortical Vit. C estimation', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Leukocyte vitamin C\n\nLeukocyte concentration of vitamin is a better indicator of body store, it may be deficient even in the absence of clinical signs of deficiency.\nIt is estimated by buffy coat preparation.\n\n\u200b \nPlasma vitamin C\n\nPlasma ascorbic and levels vary widely and cannot be relied upon to detect early vitamin C deficiency. Urinary vitamin C\nSaturation of the tissues with vitamin C can be estimated from the urinary excretion of the vitamin after a test dose of ascorbic acid.\nExcretion of 80% of the test dose in the urine within 3-5 hr after parenteral administration is considered to be normal.\nIn vitamin C deficiency, less than 80% of test dose is excreted.', 'role': 'assistant'}]