Evaluation of Iron Deficiency Anemia
The definitive approach to evaluate iron deficiency anemia requires laboratory confirmation with hemoglobin <13g/dL in men or <12g/dL in non-pregnant women, AND ferritin <45ng/mL, followed by appropriate gastrointestinal evaluation based on patient demographics and symptoms. 1
Diagnostic Criteria and Initial Laboratory Testing
- Iron deficiency anemia is defined by hemoglobin <13g/dL in men or <12g/dL in non-pregnant women, combined with ferritin <45ng/mL 1
- Ferritin is the most powerful test for iron deficiency, with the American Gastroenterological Association recommending a cut-off of 45ng/mL rather than the traditional 15ng/mL 1
- Ferritin should be interpreted cautiously in patients with inflammatory conditions, as it's an acute phase reactant that may be falsely elevated despite iron deficiency 1
- Complete blood count with red cell indices provides sensitive indication of iron deficiency in the absence of chronic disease or hemoglobinopathy 1
- Additional laboratory tests to consider include:
Evaluation Algorithm Based on Patient Demographics
For Men and Postmenopausal Women:
- Upper and lower GI investigations should be performed in all cases of confirmed IDA unless there is significant overt non-GI blood loss 1
- Bidirectional endoscopy (upper endoscopy and colonoscopy) is strongly recommended due to higher risk of GI malignancy 1
- Colonoscopy is preferred over CT colography, but either is acceptable and preferable to barium enema 1
For Premenopausal Women:
- All premenopausal women with IDA should be screened for celiac disease 1
- Bidirectional endoscopy is conditionally recommended, with consideration for initial iron replacement therapy in younger women at low risk for GI malignancy 1
- Evaluate for menstrual blood loss as a common cause 2
Additional Testing for All Patients
- All patients should be screened for celiac disease 1
- Non-invasive testing for H. pylori should be performed, followed by treatment if positive 1
- If oesophagogastroduodenoscopy (OGD) is performed as the initial GI investigation, only the presence of advanced gastric cancer or celiac disease should deter lower GI investigation 1
- Further small bowel evaluation is not necessary unless there are symptoms suggestive of small bowel disease or if hemoglobin cannot be restored with iron therapy 1
Special Considerations
- In patients with chronic inflammatory conditions (heart failure, chronic kidney disease, inflammatory bowel disease), additional markers may be needed to assess iron status 1
- For patients with chronic kidney disease, transferrin saturation may be more reliable than ferritin as it is less affected by inflammation 1
- Faecal occult blood testing is of no benefit in the investigation of IDA 1
- Hemoglobin electrophoresis should be considered when microcytosis and hypochromia are present in patients of appropriate ethnic background to prevent unnecessary GI investigation 1
Treatment Approach
- All patients should receive iron supplementation to correct anemia and replenish body stores 1
- Oral iron is typically first-line therapy (ferrous sulfate 325 mg daily or on alternate days) 2
- Parenteral iron can be used when oral preparations are not tolerated or absorbed 1, 2
- Blood transfusions should be reserved for patients with or at risk of cardiovascular instability due to the degree of anemia 1
Follow-up
- Laboratory testing should be repeated after 8-10 weeks of treatment to assess response 3
- Patients with recurrent IDA and normal OGD and colonoscopy results should have H. pylori eradicated if present 1
- Persistent or recurrent iron deficiency requires further investigation 4
By following this systematic approach to evaluation, the underlying cause of iron deficiency anemia can be identified and appropriately treated, reducing morbidity and mortality associated with potentially serious conditions such as gastrointestinal malignancies.