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Chapter 3. Blood

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A 61-year-old woman visits her family doctor complaining of severe fatigue, which has become progressively worse over the past 6 months. She is referred to a hematologist following the results of a complete blood cell count, which shows decreased hematocrit (24%), decreased hemoglobin concentration (8 g/dL), and decreased red blood cell count 2.6 x 1012/L. The mean cell volume and reticulocyte counts are normal. Which type of anemia does the patient have?

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A Macrocytic anemia (large red cells)

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B Microcytic anemia (small red cells)

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C Normocytic, hypoproliferative anemia

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D Normocytic, hyperproliferative anemia

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E No anemia is present

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C. Low hemoglobin concentration and hematocrit demonstrate the presence of anemia. Mean cell volume is normal because the red blood cell count is reduced in proportion to the reduced hematocrit; therefore a normocytic anemia is present. The reticulocyte count is not increased, as would occur, for example, in hemorrhage or hemolytic disease, indicating that the anemia is hypoproliferative (low red cell production).

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A 21-year-old woman returns to the United States from a student exchange visit to Australia. The morning after her flight, she is awakened because she is experiencing a pain throughout her right leg, which is of pale blue color. She is taken to the emergency department, where a clinical diagnosis determines that she has deep vein thrombosis. Which of the following laboratory findings would be consistent with this history?

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A Antithrombin III defect

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B Decreased hematocrit

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C Decreased fibrinogen

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D Decreased platelet count

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E Factor VIII defect

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A. The patient is likely to be in a hypercoagulable state, predisposing her to deep vein thrombosis. Defects in anticoagulants, such as antithrombin III, produce a hypercoagulable state. Decreased platelets, fibrinogen, or factor VIII all oppose coagulation; hematocrit is not directly relevant.

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The addition of sodium citrate to banked blood inhibits coagulation. By what mechanism do citrate ions inhibit coagulation?

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A Antagonist to adenosine diphosphate

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B Antagonist to thromboxane A2

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C Binds to factor VII

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D Binds to factor X

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E Chelates Ca2+ ions

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E. Citrate ions chelate Ca2+, which is required as a cofactor for several ...

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