The patient’s presentation is consistent with iron deficiency anemia (IDA). In a patient of this age, colorectal cancer should be suspected, so colonoscopy would be the next best step.
IDA is the most common cause of microcytic anemia. Ferritin is the major physiologic storage form of iron, and low ferritin is very specific for IDA, and is generally used to diagnose IDA. However, elevated ferritin, an acute phase reactant, should be interpreted with caution in the the context of underlying inflammatory processes or neoplasia and may not necessarily correlate with excess body iron stores. Common causes of IDA include blood loss from the gastrointestinal tract and impaired absorption, such as in celiac disease. A complete history is important to evaluate for potential causes of blood loss. In older patients, gastrointestinal malignancy should always be considered and appropriately evaluated with upper endoscopy and colonoscopy if indicated.
Killip et al. present a discussion of IDA, stating it is the most common nutritional deficiency worldwide. They present algorithms to summarize the diagnosis of IDA and the subsequent evaluation of potential etiologies. Additionally, they recommend against routine screening for IDA except during pregnancy.
Rockey and Cello conducted a prospective study of 100 patients with IDA and found gastrointestinal lesions in 62 of those patients. They suggest that asymptomatic elderly patients should be evaluated first with colonoscopy and then with upper endoscopy if colonoscopy findings are negative.
Illustration A is an algorithm for the diagnosis of iron deficiency anemia.
Illustration B is an algorithm for the evaluation and management of iron deficiency anemia.
Answer 1 and 3: CT and MRI are not indicated at this time in the workup of this patient's anemia, which is most likely due to occult GI blood loss. Colonoscopy is the appropriate screening for GI malignancy. Depending on the results of the initial scope, CT or PET may be indicated to look for metastatic disease.
Answer 2: Blood transfusion is not required at this time as the patient is hemodynamically stable without severe symptoms. Patients with slow occult blood loss are less likely to require urgent transfusion as they are able to compensate over time for the volume and hemoglobin losses.
Answer 4. Gel electrophoresis can be helpful in the diagnosis of thalassemia, which is another common cause of microcytic anemia but is less likely in this demographic.
Killip S1, Bennett JM, Chambers MD. Iron deficiency anemia. Am Fam Physician. 2007 Mar 1;75(5):671-8.
PMID:17375513 (Link to Abstract)
Rockey DC, Cello JP. Evaluation of the gastrointestinal tract in patients with iron-deficiency anemia.N Engl J Med. 1993;329:1691–5.
PMID:8179652 (Link to Abstract)