How should iron deficiency anemia be diagnosed and treated?

Iron Deficiency Anemia: Diagnosis and Treatment

Start with oral iron supplementation (ferrous sulfate 325 mg daily or alternate-day dosing) for most patients with iron deficiency anemia, but use intravenous iron upfront if the patient has inflammatory bowel disease with active inflammation, malabsorption conditions, oral iron intolerance, or ongoing blood loss unresponsive to oral therapy.

Diagnosis

Laboratory Testing

• Use ferritin <45 ng/mL as the diagnostic threshold for iron deficiency in patients with anemia, as this provides optimal sensitivity and specificity 1
• In patients with inflammatory conditions (IBD, chronic kidney disease, heart failure), iron deficiency can exist with ferritin between 45-100 ng/mL 1
  • Confirm with additional testing: transferrin saturation <20%, soluble transferrin receptor, or reticulocyte hemoglobin equivalent 1, 2

Identifying the Underlying Cause

After diagnosing IDA, investigate systematically 1, 3:

• Dietary iron intake assessment
• Menstrual blood loss history in premenopausal women
• Gastrointestinal evaluation: Consider bidirectional endoscopy in men and postmenopausal women (approximately one-third have underlying GI pathology, including malignancy) 3
• Test for H. pylori infection 1
• Screen for celiac disease 1
• Review medications (NSAIDs, proton pump inhibitors)

Treatment Approach

Oral Iron Therapy (First-Line for Most Patients)

Dosing strategies 1:

• Ferrous sulfate 325 mg daily, OR
• Alternate-day dosing may improve tolerability with similar absorption rates 1
• Add vitamin C to enhance absorption 1

Common side effects include nausea, abdominal pain, and constipation, which frequently limit adherence 1.

Intravenous Iron Therapy

Use IV iron when 1, 3:

1. Patient does not tolerate oral iron
2. Ferritin levels fail to improve despite oral iron trial
3. Conditions where oral iron absorption is compromised
4. Ongoing blood loss requiring rapid repletion

Preferred formulations: Choose preparations allowing iron deficit replacement in 1-2 infusions rather than multiple doses 1

Safety considerations: True anaphylaxis is very rare; most reactions are complement activation-related pseudo-allergy (infusion reactions) and should be managed accordingly 1

Condition-Specific Management

Inflammatory Bowel Disease

• Determine if IDA results from inadequate intake/absorption versus blood loss 1
• Treat active inflammation first to enhance iron absorption 1
• Use IV iron in patients with active inflammation and compromised absorption 1

Post-Bariatric Surgery

• Use IV iron therapy in patients with procedures disrupting duodenal iron absorption who have IDA without identifiable GI blood loss 1

Celiac Disease

• Ensure strict adherence to gluten-free diet to improve iron absorption 1
• Start with oral iron supplementation based on severity and tolerance
• Progress to IV iron if stores don't improve 1

Portal Hypertensive Gastropathy

• Begin with oral iron supplements 1
• Switch to IV iron if ongoing bleeding and no response to oral therapy 1
• Consider nonselective β-blockers to treat portal hypertension when no other chronic blood loss source identified 1

Gastric Antral Vascular Ectasia (GAVE)

• If inadequate response to iron replacement, consider endoscopic therapy with band ligation or argon plasma coagulation 1

Small-Bowel Angioectasias

• Perform deep enteroscopy with distal attachment for detection and treatment 1
• Treat with ablative thermal therapies (argon plasma coagulation) or hemostatic clips 1
• Always accompany endoscopic treatment with iron replacement 1
• Reserve medical therapy for refractory cases when iron replacement and endoscopy fail 1

Common Pitfalls to Avoid

• Don't miss iron deficiency in inflammatory conditions by relying solely on ferritin >45 ng/mL—use additional markers 1
• Don't delay GI investigation in men and postmenopausal women with unexplained IDA, as malignancy may be present 3
• Don't continue oral iron indefinitely if ferritin fails to improve—switch to IV iron 1
• Don't overlook the need for multidisciplinary involvement (gastroenterology, hematology, nutrition) in complex cases 1

Treatment Goals

Iron repletion improves quality of life and decreases complications related to anemia, including fatigue, exercise intolerance, worsening heart failure, and cognitive symptoms 1, 2. The goal is to replenish iron stores and normalize hemoglobin, not just treat symptoms.