The clinical presentation is suggestive of iron deficiency anemia from an occult gastrointestinal bleed. The laboratory profile for iron deficiency anemia is associated includes low serum iron, ferritin, and transferrin saturation and an elevated total iron binding capacity.
Iron deficiency causes a microcytic anemia due to decreased heme synthesis. It is the most common cause of anemia worldwide. Causes include chronic blood loss (e.g. gastrointestinal malignancy, peptic ulcer disease, menstruation, or parasitic infections), dietary deficiency, or celiac sprue. The new finding of iron deficiency anemia in an elderly person is suspicious for gastrointestinal malignancy until proven otherwise. Iron deficiency anemia progresses through several stages: consumed iron stores, followed by decreased ferritin and iron levels, and a progression from normocytic normochromic to microcytic hypochromic anemia on peripheral blood smear.
Short and Domagalski present an algorithm for the diagnostic workup of iron deficiency anemia. They consider decreased ferritin the most accurate test to diagnose iron deficiency anemia. If a diagnosis is unclear, they suggest measuring the soluble transferrin receptor level. This is an indirect measure of erythropoiesis and is increased in iron deficiency anemia. It is unaffected by inflammatory states and can help identify concomitant iron deficient anemia in patients with anemia of chronic disease.
Del Giudice et al. performed a systematic review of the diagnostic accuracy of clinical features associated with colorectal cancer presenting in primary care. They cite studies showing that the highest positive predictive value of iron deficiency anemia in predicting colorectal cancer were found in men aged 70-79 and women aged 80-89.
Figure A depicts iron deficiency anemia on a blood smear. Note large zones of central pallor in the red blood cells as well as poikilocytosis (abnormally shaped red blood cells).
Answer 2: This is a pattern associated with iron overload in hemochromatosis.
Answer 3: This is a pattern associated with anemia of chronic disease.
Answer 4: This is a pattern associated with folate deficiency, which leads to a megaloblastic anemia.
Answer 5: This is a pattern associated with vitamin B12 deficiency, which leads to a megaloblastic anemia.
Short MW, Domagalski JE. Iron deficiency anemia: evaluation and management. Am Fam Physician. 2013 Jan 15;87(2):98-104.
PMID:23317073 (Link to Abstract)
Del Giudice ME, Vella ET, Hey A, et al. Systematic review of clinical features of suspected colorectal cancer in primary care. Can Fam Physician. 2014 Aug;60(8):e405-15.
PMID:25122831 (Link to Abstract)