Paper II — 2025 March (Supplementary (SAY)) (2019 Scheme) — Q6
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Paper II
2025 March (Supplementary (SAY)) (2019 Scheme) · 100 marks · 180 min
Question
A 35 year male presented with cough, fever since the past three weeks and weight loss. Blood
counts were normal with raised ESR. Chest x-ray showed right upper lobe consolidation.
(a) What is the clinical diagnosis and probable causative agent. 2 mark(s)
(b) Describe the laboratory diagnosis with special emphasis on rapid diagnostic methods. 4 mark(s)
Q66 marksShort Essays
Answer
(a) Clinical diagnosis and probable causative agent: Pulmonary tuberculosis, caused by Mycobacterium tuberculosis — chronic cough (>3 weeks), fever, weight loss, raised ESR, and right upper lobe consolidation on chest X-ray (the classical apical/upper-lobe predilection of post-primary/reactivation TB, reflecting the organism’s preference for well-aerated, higher-oxygen-tension lung zones) is the classical presentation.
(b) Laboratory diagnosis, with emphasis on rapid diagnostic methods:
Sputum smear microscopy (Ziehl-Neelsen staining, or the more sensitive fluorescent auramine-rhodamine stain) — rapid, cheap, widely available, but limited by the need for a relatively high bacillary load to be reliably positive.
CBNAAT/GeneXpert MTB/RIF — the key rapid diagnostic method: a cartridge-based, automated real-time PCR assay delivering results within about 2 hours while simultaneously detecting rifampicin resistance, a practical, fast proxy for likely MDR-TB; the preferred initial test in India’s National TB Elimination Programme.
Truenat MTB/MTB-Rif — a portable, chip-based real-time PCR platform usable at peripheral health-facility level, offering similarly rapid, decentralized testing.
Culture — on Löwenstein-Jensen solid medium (slow, 3–8 weeks) or automated liquid culture systems (e.g., BACTEC MGIT, faster at roughly 1–3 weeks) — remains the diagnostic gold standard and the only method enabling full phenotypic drug-susceptibility testing.
Line Probe Assay (LPA) — PCR-based hybridization assay detecting mutations conferring resistance to first- and second-line drugs, for detailed drug-resistance profiling.
Tuberculin skin test (Mantoux)/Interferon-Gamma Release Assay (IGRA) — detect immune sensitization (evidence of infection, past or present) rather than active disease directly, and cannot distinguish latent from active TB on their own.
Chest X-ray — supportive (upper-lobe infiltrates/consolidation, as in this patient), not diagnostic alone.
