**Question:** Which of the following conditions is associated with Coomb's positive hemolytic anaemia:

A. Autoimmune haemolytic anaemia
B. DIC (Disseminated Intravascular Coagulation)
C. Paroxysmal cold haemoglobinuria
D. Infective Haemolytic Anaemia

**Core Concept:**
Coomb's test is a laboratory test that detects antibodies or other factors that can cause haemolytic anaemia. Coomb's positive haemolytic anaemia refers to a type of haemolytic anaemia where the blood clotting factors are involved in the destruction of red blood cells. This can result from autoimmune reactions, clotting disorders, or infections.

**Why the Correct Answer is Right:**
Coomb's positive haemolytic anaemia is associated with autoimmune haemolytic anaemia because in this condition, there is the presence of autoantibodies directed against red blood cell (RBC) antigens. These autoantibodies cause the RBCs to be destroyed prematurely in the spleen and liver, leading to anemia.

**Why Each Wrong Option is Incorrect:**

A. **Disseminated Intravascular Coagulation (DIC)**: DIC is a condition characterized by the activation of coagulation pathways leading to excessive clot formation and consumption of clotting factors. It is not associated with Coomb's positive haemolytic anaemia.

B. **DIC**: Similar to option A, Disseminated Intravascular Coagulation (DIC) is a condition characterized by excessive clot formation and consumption of clotting factors, but it is not associated with Coomb's positive haemolytic anaemia.

C. **Paroxysmal Cold Haemolytic Anaemia (PCHA)**: PCHA is a rare acquired autoimmune haemolytic anaemia triggered by exposure to cold temperatures. It is not associated with Coomb's positive haemolytic anaemia.

D. **Infective Haemolytic Anaemia**: This option refers to a type of haemolytic anaemia caused by infections. However, infective haemolytic anaemia is not associated with Coomb's positive haemolytic anaemia.

**Clinical Pearl:**

Coomb's test is a valuable diagnostic tool in identifying the cause of haemolytic anaemia, particularly in cases where the cause is not immediately apparent. A positive result on the Coomb's test narrows down the possible causes of haemolytic anaemia, leading to more targeted and appropriate treatment. Understanding the clinical presentation and relevant laboratory tests can help in reaching a correct diagnosis and appropriate management of patients with haemolytic anaemia.