This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Systemic Bacteriology (Gram Positive Bacilli, Gram Negative Bacilli), Subject name: Microbiology
[{'content': 'When should you perform Widal test in a case of Typhoid? \nSelect and explain. \nA. 1st week, B. 2nd week, C. 3rd week, D. 4th week', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Lab diagnosis for typhoid B - Blood culture - 1st week A - Agglutination Test - 2nd week S - Stool culture - 3rd week U - Urine culture - 4th week Widal test Highly sensitive but poorly specific Also biological false positive in - Infectious mono nucleosis Malaria SLE For Widal paired testing should be done', 'role': 'assistant'}]