A nurse is caring for a client whose history reveals the clinical manifestations of pernicious anemia. The nurse should anticipate a prescription for which of the following diagnostic tests?

Choice A rationale The white blood cell count measures immune response and infection status. Normal ranges are typically 5,000 to 10,000 mm. In pernicious anemia, the primary deficit is vitamin B12, not an acute infection or primary leukocytic disorder. While severe B12 deficiency can occasionally cause mild leukopenia due to abnormal DNA synthesis in bone marrow, it is not a diagnostic gold standard for confirming this specific type of megaloblastic anemia. Choice B rationale Activated partial thromboplastin time assesses the intrinsic and common coagulation pathways. Normal values range from 30 to 40 seconds. Pernicious anemia involves an inability to absorb vitamin B12 due to a lack of intrinsic factor from gastric parietal cells. Coagulation studies do not identify vitamin malabsorption or macrocytic changes in red blood cells. Therefore, this test is irrelevant for diagnosing the underlying cause of the client's hematologic manifestations or B12 status. Choice C rationale The Sickledex test is a screening tool used to detect the presence of hemoglobin S, which is characteristic of sickle cell trait or sickle cell disease. It does not evaluate for vitamin B12 levels or the presence of megaloblastic cells. Pernicious anemia is a macrocytic anemia, whereas sickle cell is a structural hemoglobinopathy. Using a sickle cell screen would provide no useful diagnostic data regarding gastric intrinsic factor deficiencies. Choice D rationale The Schilling test is specifically designed to determine the cause of vitamin B12 deficiency. It involves administering radioactive B12 and measuring its excretion in the urine. This helps distinguish between malabsorption caused by intestinal issues and malabsorption caused by a lack of intrinsic factor, which defines pernicious anemia. By evaluating how the body handles B12 with and without added intrinsic factor, clinicians can confirm the diagnosis of this specific autoimmune-related anemia.