**Question:** In a case of Kala-azar, the aldehyde test becomes positive after -

**Core Concept:** Kala-azar is a severe form of leishmaniasis caused by Leishmania donovani, transmitted by sandflies. The aldehyde test is a diagnostic tool used to detect the presence of Leishmania parasites.

**Why the Correct Answer is Right:** The aldehyde test is positive in Kala-azar because Leishmania donovani has a unique glycolipid called lipophosphoglycan (LPG) on its surface. This LPG contains aldehyde groups which react with anti-LPG antibodies in the test, leading to a positive test result.

**Why Each Wrong Option is Incorrect:**

A. False: The aldehyde test is specific to Kala-azar, not false positive for other diseases.
B. False: The test is specific to Kala-azar, not false negative for other diseases.
C. False: The test is specific to Kala-azar, not false negative for other diseases.
D. False: The test is specific to Kala-azar, not false positive for other diseases.

**Clinical Pearl / High-Yield Fact:** The specific nature of the aldehyde test for Kala-azar makes it a reliable diagnostic tool in endemic areas, allowing for rapid, accurate diagnosis of the disease.

**Correct Answer:**

**Correct Answer:** C. False: The test is specific to Kala-azar, not false negative for other diseases.

This indicates that the aldehyde test is highly specific for Kala-azar, meaning it is very unlikely to produce a false negative result for a patient with Kala-azar. The test is not affected by other diseases, ensuring its reliability in diagnosing Kala-azar in endemic areas.