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': 'Which of the following has no role in the diagnosis of childhood TB? \nSelect and explain. \nA. ELISA, B. Mantoux, C. CXR, D. FNAC', 'role': 'user'}, {'content': "Answer: A \nExplanation: Lab investigations of pediatric TB\n\nESR and blood count: No value in diagnosis or follow up of TB.\nDemonstration of AFB: Children don't expectorate out sputum, but swallow it. Therefore sputum is not available for examination. A laryngeal swab may be obtained for smear and culture examination for mycobacteria. It is customary to examine the gastric lavage in children for bacteriological examination on 3 consecutive days. Aspiration of early morning gastric contents (before breakfast) is done with a Ryle's tube and sent for bacteriological examination. Adding vancomycin to the sample improves the yield of mycobacterium. The CSF, Pleural fluid or bronchial aspirate, urine and discharges from tuberculosis sinuses are examined for tubercle bacilli.\nHistopathology: Material for histopathology may be obtained by biopsy or FNAC.\nPCR: High sensitivity and specificity for pleural fluid and low for gastric aspirate.\nCXR and CT may show characteristic features.\nUSG may be helpful for the detection of enlarged abdominal lymph nodes.\nSerology: Elisa or other methods have no utility in pediatric TB.", 'role': 'assistant'}]