- The lepromin skin test is used to determine what type of leprosy a person has.
- It is a prognostic test that is very helpful in classifying leprosy.
- It is similar to tuberculin test
- It cannot be used for diagnostic purpose since it is positive in a significant number of normal people and is negative towards the lepromatous pole of the disease.
- It is based on delayed type of hypersensitivity (DTH)
- Kensuke Mitsuda published the first paper leading to the lepromin reaction (1919). It involves the injection of a standardized extract of the inactivated “leprosy bacillus”,(Mycobacterium leprae or “Hansen’s Bacillus”) under the skin.
- Two types of antigens are available:
- Mitsuda lepromin, an autoclaved suspension of tissue (whole bacilli) obtained from experimentally infected armadillos (Lepromin A);
- Dharmendra lepromin, a purified chloroform-ether extracted suspension of M. leprae (fractionated bacilli with soluble protein component).
- In India, lepromin antigen is prepared by the Central Leprosy Teaching and Research Institute, Chengalpattu, Tamil Nadu.
Lepromin Test Procedure
An extract sample o.1 mL of inactivated Hansen’s Bacillus/ lepromin(antigen) is intradermally injected just under the skin, usually on the forearm. The injection site is labeled and examined 3 days and 28 days later to see if there is a reaction.
The introduction of lepromin injection gives two types of reactions (diphasic responses).
- Early reaction of Fernandez– erythema develops in 24-48 hours and remains for 3-5 days.
- Late reaction of Mitsuda– nodule appears after 1-2 weeks.
Applications of lepromin test
- Classificationof leprosy patients
- lepromin test is positive for tuberculoid type of leprosy
- Negative in lepromatous type
- Assessment the prognosis:
- A positive reaction indicates good prognosis and a negative a bad prognosis. negative to positive indicate good treatment.
- Assessment resistance of individuals to leprosy
- Positive lepromin test indicates resistance to Leprosy disease.
