Which of the following statements regarding anemia in hospitalized patients is MOST correct?A. A low serum iron, normal or low serum ferritin, and normal or high total iron-binding capacity are associated with iron-deficiency anemia
Correct Answer: A
Reasons for anemia in hospitalized patients are myriad and can include exacerbation of an underlying disease, blood loss from procedures, hemodilution from fluid administration, and impaired erythropoiesis. Phlebotomy for diagnostic purposes is also major cause of anemia. One study showed that 74% of patients developed anemia during their hospitalization.
Evaluation of the RBC indices can help determine the cause of anemia. The mean corpuscular volume (MCV) is the average volume of the patient’s RBC and can be low, normal, or elevated. Microcytic RBCs are formed because of decreased production of hemoglobin, which can be due to abnormal globin (thalassemias) or heme (sideroblastic anemias) production or lack of iron (iron-deficiency, anemia of inflammation). Iron studies can help elucidate the cause of microcytic anemias. Iron-deficiency anemia is characterized by low serum iron, a high transferrin, and low ferritin levels. Anemia of inflammation is associated with low iron levels due to reduced iron absorption from the gastrointestinal tract as well as decreased release of iron from body stores. The serum transferrin is usually normal to low and serum ferritin is usually normal to high. Serum iron and ferritin levels are usually normal to high in sideroblastic anemias and thalassemias.
An elevated MCV (macrocytic) is usually due to red cell membrane defects or DNA synthesis defects. Defects in DNA synthesis is associated with folate or vitamin B12 (cobalamine) deficiency, abnormal RBC maturation (eg myelodysplastic syndrome), or certain chemotherapeutic medications. Liver disease or hypothyroidism can cause red cell membrane defects.
However, the RBCs are normal sized (normocytic) in many cases. In these cases, it may be helpful to determine the mechanism underlying the anemia. Mechanisms leading to anemia include decreased RBC production, increased RBC destruction, and blood loss. These mechanisms are not mutually exclusive and can be operating at the same time in a patient.
The reticulocyte count can help distinguish between decreased RBC production and increased RBC destruction. However, because the reticulocyte count is often reported as a percentage of all RBCs, it can be falsely elevated in anemia. Furthermore, younger reticulocytes with a longer lifespan are released into the circulation in the setting of anemia. The reticulocyte production index is a calculated index that corrects for both hematocrit and reticulocyte lifespan.