Which test result is most useful for tailoring antitubercular therapy by identifying the pathogen's drug susceptibility?

• A. Culture and sensitivity
• B. X-ray
• C. Complete blood count
• D. Positive sputum culture

Answer: (A)

The key idea is that choosing the right drugs for TB hinges on knowing which drugs actually kill the bacteria in this patient. That information comes from culture combined with drug susceptibility testing. Growing the Mycobacterium tuberculosis from the patient allows a controlled test of how the organism responds to standard anti-TB drugs. The susceptibility results tell you which drugs the strain is susceptible to and which it resists, so the regimen can be tailored to avoid ineffective meds and address any resistance patterns, including MDR-TB.

Other results can help with diagnosis or disease extent—imaging shows radiographic involvement, and a complete blood count or a positive culture confirms infection—but they don’t reveal drug susceptibility. That MDT (culture with sensitivity testing) step is what directly guides which drugs to use.