What is the workup for iron deficiency anemia?

Comprehensive Workup for Iron Deficiency Anemia

The workup for iron deficiency anemia should include serum ferritin as the primary diagnostic test, followed by a complete gastrointestinal evaluation with upper and lower endoscopy to identify the underlying cause, particularly in adult men and postmenopausal women. 1, 2

Diagnostic Laboratory Testing

• Serum ferritin is the most powerful test for diagnosing iron deficiency, with a concentration <12 μg/dL being diagnostic of iron deficiency 1
• In patients with concurrent inflammation, malignancy, or hepatic disease, ferritin may be falsely elevated; a higher threshold (<100 μg/L) should be used to diagnose iron deficiency in these cases 1, 2
• Complete blood count with red cell indices provides sensitive indication of iron deficiency in the absence of chronic disease or hemoglobinopathy 1, 2
• Microcytosis (low MCV) is characteristic of iron deficiency but may also occur in thalassemia and other hemoglobinopathies 1
• Elevated red cell distribution width (RDW >14.0%) with microcytosis strongly suggests iron deficiency anemia 2
• Transferrin saturation <30% may help confirm the diagnosis when ferritin results are equivocal 1
• Hemoglobin electrophoresis should be considered when microcytosis is present in patients of appropriate ethnic background to prevent unnecessary GI investigation 1

History and Physical Examination

• Document dietary history to identify iron-deficient diets, though this alone should not be presumed as the cause of anemia 1
• Record upper and lower GI symptoms, though these rarely correlate with investigation findings 1
• Note the use of aspirin, NSAIDs, and anticoagulants, which should be discontinued when possible 1
• Obtain family history of hematological disorders (thalassemia, sideroblastic anemia), telangiectasia, and bleeding disorders 1
• In premenopausal women, assess menstrual blood loss and pregnancy status, as these are common causes of iron deficiency anemia 3

Gastrointestinal Evaluation

• GI investigations should be considered in all patients with confirmed IDA unless there is a history of significant non-GI blood loss 1
• All patients should be screened for celiac disease, as 2-3% of patients presenting with IDA have this condition 1
• Upper GI endoscopy should be performed first, with small bowel biopsies taken during the procedure 1
• Unless upper GI endoscopy reveals carcinoma or celiac disease, all adult men and postmenopausal women should undergo examination of the lower GI tract 1
• Colonoscopy is preferred over CT colography for investigation of the lower GI tract, but either is acceptable and preferable to barium enema 1
• Dual pathology (lesions in both colon and upper GI tract) occurs in 10-15% of patients, necessitating complete evaluation 1
• Further visualization of the small bowel is not necessary unless there are symptoms suggestive of small bowel disease or if hemoglobin cannot be maintained with iron therapy 1
• Faecal occult blood testing is of no benefit in the investigation of IDA 1

Special Considerations

• In premenopausal women, the approach should be more selective, with celiac disease screening recommended for all, but other GI investigations based on clinical judgment 1
• For pregnant women, higher doses of iron supplementation may be required due to increased demands 2
• In patients with recurrent IDA and normal endoscopy results, Helicobacter pylori should be eradicated if present 1
• If anemia persists despite treatment, consider other causes such as malabsorption, chronic inflammation, or rare hematologic disorders 4

Treatment Approach

• All patients should receive iron supplementation to correct anemia and replenish body stores 1
• Oral iron (100-200 mg elemental iron daily) is the initial treatment of choice for most patients 4
• An increase in hemoglobin of at least 2g/dL within 4 weeks indicates adequate response to therapy 2
• Parenteral iron can be used when oral preparations are not tolerated or in cases of malabsorption 1, 5
• Blood transfusions should be reserved for patients with or at risk of cardiovascular instability due to severe anemia 1

Common Pitfalls to Avoid

• Do not accept a positive dietary history alone as the cause of anemia without completing a full GI investigation 1
• Do not accept minor upper GI findings (such as erosions or peptic ulcer) as the sole cause of iron deficiency without completing lower GI evaluation 1
• Do not rely solely on hemoglobin and hematocrit for diagnosis, as these are late indicators of iron deficiency 2
• Do not overlook celiac disease as a potential cause, even in the absence of gastrointestinal symptoms 1
• Do not assume a normal ferritin excludes iron deficiency in patients with inflammatory conditions 2