In patients of leprosy, Lepromin test is used for:
Ans. is 'b' i.e. Prognosis [Ref: Park 20/e, p 282 (19/ep271, 18/e p258)JLepromin test is not a diagnostic test, as it may give positive result in normal subjects and negative results in lepromatous and near-lepromatous cases.Uses of Lepromin testto evaluate the immune status (cell mediated immunity) of leprosy patientsin classifying the diseaseto estimate the prognosis of leprosy patients (Lepromin test is usually strongly positive in the typical tuberculoid cases and the positivity getting weaker as one passes through the spectrum to the lepromatous end. The typical lepromatous cases are lepromin negative, indicating a failure of CMI. The lepromin negative individuals are at a higher risk of developing progressive multibacillary leprosy, but those who are lepromin positive, either escape the clinical disease or develop paucibacillary disease)Procedure and InferenceThis test is performed by injecting intradermally 0.1 ml of lepromin into the inner aspect of the forearm. Reaction is read at 48 hrs and 21 days.Two types of positive reactions have been described.Early Reaction or Fernandez reactionthis appears as an area of redness and induration at the site of inoculationit develops within 24 to 48 hrs and disappears after 3 to 4 days.the reading is taken at 48 hrs, and if the area of redness is more than 10 mm, the test is considered positive.the early reaction has been described as delayed hypersensitivity reaction to "soluble" constituents of the leprosy bacilli.Late Reaction or Mitsuda reactionthis reaction develops late, becoming apparent in 7-10 days following the infection and reaches peak in 3 or 4 weeks. A nodule develops at the site of inoculation.the reading is taken at 21 days and if the nodule is more than 5 mm in diameter, the reaction is said to be positive.the late reaction is induced by the bacillary component of the antigen. It indicates cell mediated immunity.The early positive reaction indicates whether or not a person has been previously sensitized by exposure to an infection by leprosy bacilli. It is thus more superior to late reaction.The early reaction corresponds to the Mantoux reaction in tuberculosis.Also Know:In the first 6 months of life, most children are lepromin negative; gradually with increasing age more and more persons become positive.BCG vaccination can convert lepra reactions from negative to positive in large no. of individuals.
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