How should iron deficiency anemia be managed?

Laboratory Interpretation and Management of Severe Iron Deficiency Anemia

Critical Laboratory Findings

This patient has severe iron deficiency anemia requiring immediate iron replacement therapy and comprehensive gastrointestinal evaluation. 1

Key Abnormalities:

• Hemoglobin: 8.1 g/dL (severely low, normal 11.1-15.9 g/dL) 1
• Ferritin: 5 ng/mL (critically low, normal 15-150 ng/mL) - confirms absolute iron deficiency 1
• Iron saturation: 3% (severely depleted, normal 15-55%) 1
• MCV: 71 fL (microcytic, normal 79-97 fL) 1
• MCH: 18.6 pg (hypochromic, normal 26.6-33.0 pg) 1
• MCHC: 26.3 g/dL (hypochromic, normal 31.5-35.7 g/dL) 1
• RDW: 16.9% (elevated, indicates mixed red cell populations) 1

The combination of ferritin <15 ng/mL with transferrin saturation <15% definitively confirms iron deficiency anemia. 1

Immediate Management Algorithm

Step 1: Initiate Iron Replacement Therapy

Start oral iron supplementation immediately with ferrous sulfate 325 mg daily (containing 65 mg elemental iron) or on alternate days. 1, 2, 3

• Optimal administration: Take on an empty stomach with 500 mg vitamin C to enhance absorption 1
• If gastrointestinal side effects occur (nausea 11%, constipation 12%, diarrhea 8%), consider taking with meals or switching to alternate-day dosing 1
• Alternative formulations include ferrous fumarate or ferrous gluconate if ferrous sulfate is not tolerated 1
• Continue iron therapy for 3 months after hemoglobin normalization to replenish iron stores 1

Step 2: Mandatory Gastrointestinal Investigation

All postmenopausal women and men with confirmed iron deficiency anemia require comprehensive gastrointestinal evaluation to exclude malignancy, regardless of symptoms. 1

Upper GI Evaluation:

• Perform esophagogastroduodenoscopy (EGD) with mandatory small bowel biopsies to screen for celiac disease (present in 2-3% of IDA patients) 1
• Upper endoscopy identifies a cause in 30-50% of patients 1
• Document and discontinue NSAIDs if being used 1

Lower GI Evaluation:

• Proceed with colonoscopy or CT colonography even if upper endoscopy reveals a lesion (unless advanced gastric cancer or celiac disease is found) 1
• Dual pathology (upper and lower GI lesions) occurs in 10-15% of patients 1
• Colonoscopy is preferred over barium enema as it allows visualization of angiodysplasia and tissue biopsy 1
• Do not accept esophagitis, erosions, or peptic ulcer as the sole cause without completing lower GI evaluation 1

Step 3: Additional Diagnostic Considerations

Screen for celiac disease in all patients with iron deficiency anemia. 1

• Obtain tissue transglutaminase antibodies or endomysial antibodies 1
• Small bowel biopsies during EGD are mandatory 1

Evaluate for Helicobacter pylori infection as it can impair iron absorption 1

Assess dietary iron intake though dietary deficiency alone should not preclude full GI investigation 1

Step 4: When to Consider Intravenous Iron

Intravenous iron should be used in specific circumstances: 1, 3

• Intolerance to oral iron despite formulation changes 1, 3
• Malabsorption conditions (celiac disease, inflammatory bowel disease, post-bariatric surgery) 1, 3
• Active inflammation with compromised absorption 1
• Ongoing blood loss unresponsive to oral therapy 1
• Need for rapid iron repletion 3, 4

Step 5: Further Investigation if Refractory

Additional small bowel evaluation is only necessary if: 1

• Anemia becomes transfusion-dependent 1
• Visible blood loss (melena) occurs 1
• Hemoglobin cannot be restored or maintained with iron therapy 1

In these cases, consider deep enteroscopy with distal attachment to detect small bowel angiodysplasias, which can be treated with argon plasma coagulation or hemostatic clips 1

Critical Pitfalls to Avoid

Do not assume menstrual blood loss is the sole cause in premenopausal women without investigating other sources if anemia is severe or refractory. 1, 5

Do not perform fecal occult blood testing - it is insensitive and non-specific and provides no diagnostic value in IDA workup 1

Do not stop investigation after finding minor upper GI lesions (esophagitis, gastritis, small ulcers) without completing lower GI evaluation 1

Do not delay investigation in patients taking NSAIDs or anticoagulants - these medications should not deter comprehensive evaluation 1

Monitoring Response

Reassess hemoglobin after 3 weeks of oral iron therapy to confirm therapeutic response 1

• Expected rise: 1-2 g/dL increase in hemoglobin 5
• If no response, consider malabsorption, ongoing blood loss, incorrect diagnosis, or non-compliance 6
• Once hemoglobin normalizes, continue iron for 3 months to replenish stores 1

Monitor hemoglobin concentration long-term to detect recurrence, especially if no definitive GI source was identified 1