Which test evaluates the extrinsic pathway?

Correct Answer: A

Rationale: The correct answer is A: PT (INR). The PT evaluates the extrinsic pathway by measuring the time it takes for blood to clot after adding tissue factor. This pathway involves factors outside the blood vessel. PTT (choice B) evaluates the intrinsic pathway, TT (choice C) evaluates the common pathway, and closure time (choice D) assesses platelet function, not the extrinsic pathway. Therefore, PT is the most appropriate choice for evaluating the extrinsic pathway.

Correct Answer: D

Rationale: The correct answer is D: Vitamin K deficiency. Prolonged PT and aPTT indicate impaired coagulation factors, which are dependent on Vitamin K for synthesis. The normal blood test rules out hemophilia A, a genetic deficiency of factor VIII (choice A), thrombocytopenia, a low platelet count (choice B), and Von Willebrand disease, a deficiency in a blood protein that helps with clotting (choice C). Therefore, the most likely diagnosis is Vitamin K deficiency due to the abnormal coagulation factors.

Correct Answer: B

Rationale: The correct answer is B: Vitamin B12 deficiency. Anemia in a strict vegetarian is likely due to inadequate intake of Vitamin B12 found in animal products essential for red blood cell production. Iron deficiency (A) is common in vegetarians but not the primary cause of anemia in this case. Erythropoietin defect (C) is rare and not specific to vegetarianism. Calcium deficiency (D) does not directly cause anemia.

Correct Answer: B

Rationale: The correct answer is B: Absolute lymphocytosis. This is the most important diagnostic criterion for Chronic Lymphocytic Leukemia (CLL). CLL is characterized by a high number of mature-looking lymphocytes in the blood. The presence of absolute lymphocytosis (>5,000/microliter) is a key feature in diagnosing CLL. Hypogammaglobulinemia (choice A) can occur in CLL but is not the primary diagnostic criterion. Male predominance (choice C) and enlarged lymph nodes (choice D) are common features of CLL but do not serve as the primary diagnostic criterion.

Correct Answer: B

Rationale: The correct answer is B: Vector infective for life. Dengue fever is caused by the dengue virus, which is transmitted to humans through the bite of infected Aedes mosquitoes. Once a mosquito is infected with the virus, it remains infective for the rest of its life, making it a lifelong vector for dengue transmission. This is why controlling mosquito populations is crucial in preventing the spread of dengue fever. Choice A (DNA virus) is incorrect because dengue fever is caused by an RNA virus, not a DNA virus. Choice C (Prefers polluted water) is incorrect as Aedes mosquitoes, the vector for dengue, breed in clean, stagnant water. Choice D (Joint symptoms more than chikungunya) is incorrect as joint symptoms are actually more common and severe in chikungunya fever, not in dengue fever.