每日一题_2023.08.20

A 43-year-old man presents to his physician with fatigue. The patient says he is concerned about his fatigue because he has a strong family history of cancer. He thinks that if his parents did not drink, smoke, and eat such poor diets they would have lived longer lives. He says that because of all this, he never drinks alcohol or smokes tobacco. He has also followed a strict vegan diet for 10 years. He says that all of his meals are high in leafy green vegetables. Laboratory tests show a hematocrit of 35% with a normal RBC distribution width. Results of a peripheral blood smear are shown in the image. Which of the following laboratory tests will most definitively determine the likely cause of his abnormal blood smear?

一名43岁男性因疲劳就诊。这名患者说，他担心自己的疲劳，因为他有很强的癌症家族史。他认为，如果他的父母不喝酒、不抽烟、不吃那么糟糕的饮食，他们就会活得更久。他说，因为这一切，他从不喝酒或吸烟。他还遵循严格的素食饮食10年。他说，他所有的食物都含有大量的绿叶蔬菜。实验室检查显示血细胞比容为35%，红细胞分布宽度正常。外周血涂片结果如图所示。下列哪项化验最能确定他的血涂片异常的可能原因?

(A) Folate level叶酸水平

(B) Homocysteine level同型半胱氨酸水平

(C) Methylmalonic acid level 甲基丙二酸水平

(D) Serum B12 level血清B12水平

(E) Urine vitamin B12 level尿维生素B12水平

答案解析：

该患者有大细胞性贫血伴超分叶中性粒细胞，这种疾病很可能是由维生素B12缺乏或叶酸缺乏引起。同型半胱氨酸水平升高提示叶酸缺乏或维生素B12缺乏，但对两者的鉴别没有帮助。

正确答案：B