This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: vitamins, Subject name: Biochemistry
[{'content': 'Diagnosis of vitamin B1 deficiency is made by \nSelect and explain. \nA. Thiamine level, B. Transketolase activity, C. Carboxylase activity, D. Transaminase activity', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Diagnosis of Vit B1 deficiency is made by Transketolase activity.Biochemical Parameters In thiamine deficiency, blood thiamine is reduced, but pyruvate, alpha-ketoglutarate and lactate are increased. Erythrocyte transketolase activity is reduced; this is the earliest manifestation seen even before clinical disturbances.Reference: Textbook of Biochemistry by D M Vasudevan, sixth edition pg no. 392', 'role': 'assistant'}]