This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Communicable & Non Communicable Disease, Subject name: Social & Preventive Medicine
A 30 year old male came with complaint of cough and fever from last 6 weeks. On lab investigations, patient came sputum smear negative and no significant findings were seen on chest X-ray. The consultant is having high suspicion that patient is having TB. What is the next step for managing such a patient? 
Select and explain. 
A. Repeat chest X-ray, B. Do CBNAAT, C. Sta ATT, D. Repeat sputum examination
B: Do CBNAAT
Answer: B: Do CBNAAT 
Explanation: When clinical suspicion is high with negative findings on sputum smear examination and CXR, then CB-NAAT is the next diagnostic modality to be done. It detects mycobacterium tuberculosis in the sample. if MTB is positive, we also test for rifampicin senstivity.