A 28-year-old healthcare worker in India undergoes pre-employment tuberculosis screening with a Mantoux tuberculin skin test. Induration measured at 72 hours is 12 mm. The worker has no symptoms, no known TB contact, no immunosuppression, and received BCG vaccination in infancy. What does this result indicate?
- A Negative; no further action needed
- B Positive; likely due to BCG vaccination and not specific for TB infection
- C Positive; indicates latent TB infection requiring treatment ✓
- D Equivocal; repeat test after 2 weeks
Correct answer: C. Positive; indicates latent TB infection requiring treatment
Explanation
As per Indian NTEP/ICMR guidelines, Mantoux induration ≥10 mm is considered positive in healthcare workers regardless of BCG history. BCG causes induration usually <10 mm and wanes over years. In a healthcare worker, 12 mm meets the cutoff for LTBI. The option claiming BCG as the cause is the tempting distractor, but the cutoff supersedes BCG interpretation in high-risk groups.
Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.