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Diagnosis

The cardinal signs of leprosy are

  • Hypopigmentation

  • Anaesthesia or hypoaesthesia

  • Nerve thickening

  • Presence of acid fast bacillus in the skin smear.


A diagnosis of leprosy can be made if any two of i. _ iii are present or iv is present.

Slit skin

smear: This test demonstrates the presence of acid fast bacillus in the skin. A small superficial incision is made in the skin without drawing blood and the serous material from the bottom is smeared on the glass slide and stained with Ziehl Neelsen
stain. It is viewed under the oil immersion microscope. The commonest areas where the skin smear is positive at the earliest and becomes negative the last are the ear lobes and the dorsa of fingers.

The severity of the disease and the progress during treatment can be assessed by one of two indices.

The bacteriological index is given value as follows:

  • 6 + Many clumps of bacilli in the average field (over 100)

  • 5 + 100-1000 bacilli/field

  • 4 + 10-100 bacilli/field

  • 3 + 1-10 bacilli/field

  • 2 + 1-10 bacilli in co-fields

  • 1 + 1-10 bacilli in co-fields

In the bacteriological index both the viable and the nonviable forms are taken into account. Hence the more sensitive index is the Morphological Index (M.I.) which is expressed as a number being the ratio of solid forms to that of the total Bacillary count.