**Question:** Coomb's + ve Hemolytic Anaemia is seen in all except-

A. Dengue fever
B. Sickle cell anaemia
C. Thalassemia
D. Malaria

**Core Concept:**

Coomb's test, also known as Coomb's or Direct Antiglobulin Test (DAT), is a laboratory test used to detect the presence of antibodies against red blood cell (RBC) antigens in a patient's serum. Coomb's +ve Hemolytic Anaemia occurs when there are antibodies in the blood that cause destruction of RBCs, leading to hemolysis. The correct answer should not be a condition where antibodies are present to cause hemolysis.

**Why the Correct Answer is Right:**

Dengue fever is an acute viral infection caused by dengue virus. Although it can cause anemia, it's not a hemolytic anemia due to the absence of antibodies that cause direct destruction of RBCs. Dengue fever primarily causes hemolysis through indirect mechanisms like tissue damage and leakage, not by hemolysis due to antibodies.

**Why Each Wrong Option is Incorrect:**

**A. Dengue:** As mentioned above, dengue fever does cause anemia but not due to hemolysis by antibodies.

**B. Sickle cell anaemia:** This is a genetic disorder characterized by sickle-shaped RBCs. While it can cause hemolysis due to the deformity of RBCs, it is not a Coomb's +ve Hemolytic Anaemia.

**C. Thalassemia:** Thalassemia is a group of hereditary disorders characterized by reduced RBC production and hemolysis. However, it's not a Coomb's +ve Hemolytic Anaemia. Thalassemia primarily causes hemolysis indirectly due to reduced RBC production and altered RBC shape, not due to antibodies causing direct destruction of RBCs.

**D. Malaria:** Malaria is a parasitic infection caused by Plasmodium species. It can lead to hemolysis through direct invasion of RBCs, not due to Coomb's +ve Hemolytic Anaemia. Malaria primarily causes hemolysis through parasite invasion and damage to the RBCs, not due to antibodies causing direct destruction of RBCs.

**Clinical Pearl:** Hemolytic Anaemias due to Coomb's +ve Hemolytic Anaemia are primarily caused by autoantibodies produced in response to autoimmune conditions, drugs, or infections. In contrast, the mentioned conditions cause hemolysis through different mechanisms.