Which of the following is not the criteria in the international prognostic index for non Hodgkin's lymphoma?

Correct Answer: C

Rationale: The correct answer is C: Lymphocyte count. In the International Prognostic Index for Non Hodgkin's Lymphoma, the criteria are based on the number of extranodal sites, LDH level, and performance status. Lymphocyte count is not included in the IPI criteria because it does not play a significant role in predicting the prognosis of Non Hodgkin's Lymphoma. Lymphocyte count is not a commonly used parameter in prognostic scoring systems for this type of cancer. Therefore, the absence of lymphocyte count as a criteria in the IPI is justified.

Correct Answer: D

Rationale: The correct answer is D: Aplastic anemia. Aplastic anemia is characterized by pancytopenia, which includes low hemoglobin levels leading to anemia. The dry tap marrow indicates bone marrow failure, which is a hallmark of aplastic anemia. The subcutaneous petechiae are due to thrombocytopenia, another feature of this condition. Iron deficiency anemia (A) typically presents with microcytic hypochromic red blood cells and is not associated with bone marrow failure. Megaloblastic anemia (B) is characterized by macrocytic red blood cells and is usually due to deficiencies in vitamin B12 or folate. Hemolytic anemia (C) involves the premature destruction of red blood cells and is not typically associated with bone marrow failure.

Correct Answer: C

Rationale: The correct answer is C, Microangiopathic hemolytic anemia. Schistocytes are fragmented red blood cells caused by mechanical damage as they pass through narrowed vessels. This occurs in conditions like thrombotic thrombocytopenic purpura and hemolytic uremic syndrome, which are types of microangiopathic hemolytic anemia. Sickle cell trait (A) and Thalassemia (B) are genetic disorders affecting red blood cell structure and production, not causing mechanical fragmentation. Idiopathic thrombocytopenic purpura (D) is a disorder characterized by low platelet count, unrelated to RBC fragmentation.

Correct Answer: C

Rationale: The correct answer is C: Platelets change their shape during the process of platelet aggregation in vascular injury. Platelets undergo shape change from a discoid to a spiky form, leading to the exposure of their glycoprotein receptors, which then bind to fibrinogen and other platelets to form a platelet plug. This process is crucial for hemostasis and preventing excessive bleeding. Explanation for why other choices are incorrect: A: There will be initial vasodilation - Vasodilation is not a direct result of platelet aggregation but rather an initial response to vascular injury to increase blood flow to the area. B: Clotting factors play no role in its formation - Clotting factors are essential for the later stages of hemostasis, but platelet aggregation is primarily driven by platelet activation and shape change. D: Serotonin stimulates platelet aggregation - While serotonin is released from platelets upon activation, it does not directly stimulate platelet aggregation.

Correct Answer: B

Rationale: The correct answer is B because once a mosquito vector, usually Aedes aegypti, is infected with the dengue virus, it remains infective for life. This is due to the virus establishing a lifelong infection in the mosquito's salivary glands. A: Incorrect. Dengue is caused by an RNA virus, specifically the flavivirus. C: Incorrect. Aedes mosquitoes prefer clean, stagnant water for breeding, not polluted water. D: Incorrect. Joint symptoms are common in both dengue fever and chikungunya, but usually more severe in chikungunya.