Communicable diseases: lepromin test: practice question

A PSM question in the style of the NEET PG paper. Answer it first, then read why the right option is right and why each of the others is wrong.

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PSM · Communicable diseases: lepromin test

Sample item

A patient has a few well-defined anaesthetic skin patches and thickened nerves. A lepromin test, read at four weeks, shows a large nodular positive reaction. What does this result indicate?

AAn impending type 2 lepra reactionBGood cell-mediated immunity to M. lepraeCLepromatous disease with absent cell-mediated responseDConfirmed active leprosy with a heavy bacillary load

Original practice item, not a recalled exam question. Nothing here is recorded.

The answer and the reasoning

B. Good cell-mediated immunity to M. leprae

The late (Mitsuda) reaction to lepromin, read at about 3 to 4 weeks, reflects cell-mediated immunity and is strongly positive in tuberculoid leprosy and negative in lepromatous leprosy. It is used for classification and prognosis, not for diagnosis, and it is also positive in many healthy people.

Option by option

A. An impending type 2 lepra reaction
Lepromin reactivity does not predict erythema nodosum leprosum.
B. Good cell-mediated immunity to M. leprae (correct)
Correct. A strong positive late reaction reflects good cell-mediated immunity, as at the tuberculoid end, and helps classification rather than diagnosis.
C. Lepromatous disease with absent cell-mediated response
Lepromatous leprosy is characterised by a negative lepromin reaction.
D. Confirmed active leprosy with a heavy bacillary load
The test is not diagnostic, and a positive result points to a low bacillary load rather than a heavy one.

Source note: Original NextPrep sample item — pending expert review. This item is original practice material awaiting independent expert review, so confirm important facts in a standard textbook.

Questions about this PSM question

What is the answer to this PSM question?

The best answer is B, Good cell-mediated immunity to M. leprae. The late (Mitsuda) reaction to lepromin, read at about 3 to 4 weeks, reflects cell-mediated immunity and is strongly positive in tuberculoid leprosy and negative in lepromatous leprosy.

Why is "An impending type 2 lepra reaction" not the answer?

Lepromin reactivity does not predict erythema nodosum leprosum.

Why is "Lepromatous disease with absent cell-mediated response" not the answer?

Lepromatous leprosy is characterised by a negative lepromin reaction.

Why is "Confirmed active leprosy with a heavy bacillary load" not the answer?

The test is not diagnostic, and a positive result points to a low bacillary load rather than a heavy one.

What concept does this question test?

It tests Communicable diseases: lepromin test in PSM. It is used for classification and prognosis, not for diagnosis, and it is also positive in many healthy people.

How hard is this question?

We tag it as a multi-step question: it asks you to combine more than one idea. The tag is our own editorial judgement, not an official difficulty rating, so read the reason for every option, not only the answer.

How should I study Communicable diseases: lepromin test?

Practise biostatistics with small calculations until sensitivity, predictive values and risk measures are automatic. Then use the flashcards and the other PSM questions on this site to test what stuck.

Is this a real NEET PG question?

No. It is an original practice item (editorial status: sample, version 1). NextPrep does not publish recalled or leaked questions, and independent faculty review of this item has not been completed yet, so confirm important facts in a standard textbook.