Iron deficiency anemia

Iron deficiency is the most common cause of anemia and usually results from blood loss; malabsorption, such as with celiac disease, is a much less common cause. Symptoms are usually nonspecific. Red blood cells tend to be microcytic and hypochromic, and iron stores are low, as shown by low serum ferritin and low serum iron levels with high serum total iron-binding capacity. If the diagnosis is made, occult blood loss should be suspected until proven otherwise. Treatment involves iron replacement and treatment of the cause of blood loss. Iron is absorbed in the duodenum and upper jejunum. Iron absorption is determined by its source and by what other substances are ingested with it. Iron absorption is best when food contains heme iron (meat). Dietary nonheme iron is usually in the ferric state (+3) and must be reduced to the ferrous state (+2) and released from food binders by gastric secretions. Nonheme iron absorption is reduced by other food items (eg, vegetable fiber phytates and polyphenols; tea tannates, including phosphoproteins; bran) and certain antibiotics (eg, tetracycline). Ascorbic acid is the only common food element known to increase nonheme iron absorption. The average American diet, which contains 6 mg of elemental iron/1000 kcal of food, is adequate for iron homeostasis. Of about 15 mg/day of dietary iron, adults absorb only 1 mg, which is the approximate amount lost daily by cell desquamation from the skin and intestine. In iron depletion, absorption incre...

The AGA defines anemia as a hemoglobin level of less than 13 g per dL (130 g per L) in men and less than 12 g per dL (120 g per L) in patients who are not pregnant. Serum ferritin testing is commonly used to diagnose iron deficiency in patients with anemia. Based on a systematic review, the AGA recommends using a ferritin threshold value of less than 45 ng per mL (45 mcg per L) for diagnosing iron deficiency in patients with anemia. This threshold has 85% sensitivity and 92% specificity for iron deficiency. Without anemia, the ferritin threshold for iron deficiency is uncertain. Ferritin testing is less accurate in patients with chronic inflammatory conditions or chronic kidney disease, and additional tests including serum iron, transferrin saturation, soluble transferrin receptor, and C-reactive protein can help diagnose iron deficiency. Helicobacter pylori infection is associated with iron deficiency caused by atrophic gastritis and hypochlorhydria, which reduce iron absorption. Treating H. pylori infection improves the benefit of iron supplementation in anemia. After negative bidirectional endoscopy results, the AGA suggests noninvasive testing and treatment for H. pylori in IDA by urea breath testing, although stool antigen testing and serology can also be used. Celiac disease is another common cause of iron deficiency. The AGA suggests serologic testing for celiac disease in patients with iron deficiency, especially those with a family history of the disease, a person...