Paper II
Question
Describe collection of specimens in a case of suspected leprosy.
Answer
Collection of specimens in a case of suspected leprosy:
- Slit-skin smear (SSS) — the standard specimen for direct demonstration of Mycobacterium leprae. A small incision is made at the selected site (typically the earlobes and 2–3 active skin lesions), the site is squeezed to minimize blood contamination, and the dermal tissue fluid/scraping is collected by scraping the cut surface with a scalpel blade, then smeared onto a glass slide. Standard sites: both earlobes, plus lesions selected from the trunk/limbs, chosen from the most active/infiltrated edge of a representative lesion. Smears are stained with the Ziehl-Neelsen (modified, weak acid-fast) stain, and the bacteriological index (BI) and morphological index (MI) are calculated to assess bacterial load and proportion of viable (solid-staining) bacilli — important for classification and monitoring treatment response.
- Skin biopsy — a full-thickness punch biopsy taken from the active edge of a representative skin lesion, for histopathological examination (demonstrating granulomatous inflammation with or without acid-fast bacilli, and helping classify the leprosy type across the Ridley-Jopling spectrum).
- Nerve biopsy — occasionally performed (from an affected sensory/cutaneous nerve, e.g., sural or radial cutaneous nerve) in cases of suspected pure neuritic leprosy without skin lesions, for histopathological confirmation.
- Nasal smear/scraping — historically used, given nasal mucosal involvement in lepromatous leprosy, though less commonly performed now compared to slit-skin smear.
General precautions: specimens should be collected using standard aseptic technique with attention to minimizing bleeding (which dilutes/washes away bacilli), and slides should be clearly labelled with site of collection for correlation with clinical findings.