Visceral leishmaniasis (kala-azar) diagnosis in a patient from Bihar with fever, splenomegaly, and progressive wasting. Which combination of tests provides HIGHEST diagnostic sensitivity?
- A rK39 rapid diagnostic test (RDT) plus splenic aspirate smear — combined sensitivity >98% ✓
- B Bone marrow aspirate Giemsa stain alone
- C Leishmanin skin test (Montenegro test) — positive in active disease
- D Peripheral blood thick smear — Leishman-Donovan bodies visible at low parasitaemia
Correct answer: A. rK39 rapid diagnostic test (RDT) plus splenic aspirate smear — combined sensitivity >98%
Explanation
rK39 RDT (detecting anti-rK39 IgG, a kinesin-related protein specific to L. donovani complex) has sensitivity of 93–100% in Indian VL and combined with splenic aspirate smear (sensitivity 93–99%, gold standard for parasite detection) provides near-perfect diagnostic accuracy. Leishmanin (Montenegro) test becomes NEGATIVE in active VL due to anergy and converts positive only after treatment/recovery — it cannot be used for active disease diagnosis. Peripheral blood smear has poor sensitivity (<10%). Bone marrow is less sensitive than splenic aspirate.
Reference: Ananthanarayan & Paniker's Textbook of Microbiology, 11th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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