PE31.{2,5-8} | Tuberculosis Diagnosis Workflow — Summary & Reflection

KEY TAKEAWAYS

The TB diagnostic workflow in children centres on five interlocking skills: (1) Contact history elicitation and BCG scar identification (PE31.5) — the entry point to any workup; (2) Mantoux TST — 0.1 mL PPD intradermal, read induration at 48–72 h; positive ≥10 mm standard or ≥5 mm in immunocompromised/SAM; false-negative in miliary TB, HIV, malnutrition; (3) Microbiological sampling — gastric aspirate (×3 mornings, neutralised) is the standard non-sputum sample in children; FNAC for lymphadenitis; CSF for TBM; (4) CBNAAT/GeneXpert — first-line rapid molecular test; detects MTB DNA + rifampicin resistance in <2 h; sensitivity ~70–80% in paediatric pulmonary TB; negative result does NOT exclude TB; (5) Blood tests + CXR interpretation (PE31.6) — CBC, ESR, CRP, ADA supportive; CXR hilar lymphadenopathy is the key paediatric sign. Integrate all evidence into the NTEP/IAP category: confirmed (microbiological), probable (clinical-epidemiological), or possible (insufficient evidence).

REFLECT

Return to the 4-year-old girl in the opening scenario. Her father completed TB treatment 8 months ago; she has 5 weeks of fever and weight loss. You have now learned the complete diagnostic workflow. (1) Draft the contact history questions you would ask the mother. (2) How would you interpret a Mantoux induration of 8 mm in this child — positive or negative, and why? (3) She cannot expectorate — which sample would you collect, and how would you explain the procedure to her mother? (4) CBNAAT on the gastric aspirate is negative — does this change your management? Reflect on how the paucibacillary nature of childhood TB means the diagnostic decision rests on the weight of combined evidence, not a single positive test.