Iron Deficiency Anemia Diagnosis and Management

Diagnostic Testing

The American Gastroenterological Association recommends assessing iron status through laboratory testing, with serum ferritin as the primary marker, where levels <45 μg/L have 85% sensitivity for iron deficiency 1
In the absence of inflammation, ferritin <30 μg/L is diagnostic of iron deficiency, according to the Clinical Nutrition guideline society 2
Presence of inflammatory conditions can affect iron deficiency diagnosis, and serum ferritin up to 100 μg/L may still be consistent with iron deficiency in the presence of inflammation, as stated by the Clinical Nutrition guideline society and the American Gastroenterological Association 2, 3

The following laboratory tests are used to diagnose iron deficiency:

Test	Description
Hemoglobin concentration	Measures the amount of hemoglobin in the blood
Hematocrit	Measures the proportion of red blood cells in the blood
Complete blood count with red cell indices	Measures various parameters of red blood cells, including mean corpuscular volume (MCV) and mean corpuscular hemoglobin (MCH)
Serum ferritin	Measures the amount of ferritin in the blood, which reflects iron stores
Transferrin saturation	Measures the percentage of transferrin that is saturated with iron
Screening for celiac disease	Measures the presence of certain antibodies to diagnose celiac disease, which can cause iron deficiency anemia

Transferrin saturation below 16-20% indicates insufficient iron available for erythropoiesis, calculated as: (serum iron/TIBC) × 100, as recommended by the Centers for Disease Control and Prevention 5

The American Gastroenterological Association suggests considering bidirectional endoscopy, especially in postmenopausal women and men with iron deficiency anemia, to identify esophageal webs, strictures, and other structural causes of dysphagia 1, 6
The Centers for Disease Control and Prevention recommends additional testing, including serum ferritin, complete blood count with red cell indices, and red blood cell distribution width (RDW), which is typically elevated (>14%) in iron deficiency 5

Ferric carboxymaltose up to 1000 mg in a single 15-minute infusion, as well as iron sucrose 200 mg per dose, 10-minute infusion, and iron dextran with variable dosing based on calculated iron deficit, are recommended by the European Society of Medical Oncology and American Gastroenterological Association 7, 8
IV iron administration should be considered in cases of poor response to oral iron, intolerance to oral iron, need for rapid iron repletion, or failure of first-step oral therapy, as recommended by Clinical Nutrition and the American Gastroenterological Association 9, 3
Intravenous iron may be considered in patients with poor response to oral iron, intolerance to oral iron, severe anemia, or inflammatory conditions, as suggested by the American Gastroenterological Association, American College of Gastroenterology, and American Society of Hematology 3, 10, 11

Repeat hemoglobin, ferritin, and transferrin saturation tests should be conducted after 8-10 weeks of treatment, as recommended by Clinical Nutrition and the American Gastroenterological Association 9, 3
The target ferritin level is 50-100 μg/L, as suggested by Clinical Nutrition, Journal of Hepatology, European Association for the Study of the Liver, and the American Gastroenterological Association 9, 12, 13, 3
Ferritin levels should not be checked immediately after IV iron administration, as levels will be falsely elevated, according to Clinical Nutrition 9
Monthly measurement of hemoglobin and ferritin is recommended during the initial phase of treatment, as suggested by the European Association for the Study of the Liver 13

Women of reproductive age may require higher iron intake due to menstrual losses, and should be monitored closely, as suggested by the American College of Obstetricians and Gynecologists 12
Patients with chronic kidney disease (CKD) who have high ferritin levels (500-1200 ng/ml) but low Transferrin Saturation (TSAT) (<25%) may benefit from iron therapy, as recommended by the Kidney International Supplements guideline and the National Kidney Foundation 14, 15
Patients with chronic inflammatory diseases may require higher ferritin cutoffs (up to 100 μg/L) to diagnose iron deficiency, with a moderate strength of evidence, as suggested by the American Gastroenterological Association and the European Crohn’s and Colitis Organisation 3, 16
Patients with functional iron deficiency despite normal or elevated ferritin levels require special consideration, as recommended by the National Institute of Diabetes and Digestive and Kidney Diseases 12

Common gastrointestinal side effects of iron supplementation include constipation, diarrhea, and nausea, as reported by Clinical Nutrition and the European Society for Clinical Nutrition and Metabolism 9, 9
If anemia develops during treatment, the frequency of phlebotomy should be decreased if hemoglobin is <12 g/dL, and treatment should be temporarily suspended if hemoglobin is <11 g/dL, according to Journal of Hepatology and the European Association for the Study of the Liver 13, 13
If iron intolerance occurs, administration on alternate days may improve absorption and reduce side effects, as suggested by the European Society for Clinical Nutrition and Metabolism 9
Overtreatment, or iron supplementation in the presence of normal or high ferritin, is not recommended and potentially harmful, as stated by Clinical Nutrition and the European Society for Clinical Nutrition and Metabolism 9, 9
Exceeding target ferritin levels should be avoided to prevent iron overload toxicity, as recommended by the American Society of Hematology 17

The following societies have made recommendations for iron deficiency management:

Society	Recommendation
American Gastroenterological Association	Screen for celiac disease in patients with iron deficiency anemia, and confirm iron deficiency through laboratory assessment
European Crohn’s and Colitis Organisation	Use higher ferritin cutoffs (up to 100 μg/L) to diagnose iron deficiency in patients with chronic inflammatory diseases
National Kidney Foundation	Evaluate for EPO deficiency in patients with chronic kidney disease, and consider IV iron supplementation in patients with high ferritin (500-1200 ng/ml) but low transferrin saturation (<25%)
Centers for Disease Control and Prevention	Include hemoglobin concentration, hematocrit, complete blood count with red cell indices, serum ferritin, transferrin saturation, and screening for celiac disease in initial laboratory tests for suspected iron deficiency anemia
World Health Organization	Use reticulocyte hemoglobin content (CHr) to monitor treatment response, with a moderate strength of evidence

16, 18, 15, 4, 19, 20, 6, 5, 21