What is the initial workup and treatment for iron deficiency anemia?

Iron Deficiency Anemia Workup and Treatment

The initial workup for iron deficiency anemia should include serum ferritin (using a cutoff of 45 ng/mL for diagnosis), complete blood count, and screening for celiac disease, followed by bidirectional endoscopy for men and postmenopausal women with newly diagnosed IDA. 1

Diagnostic Criteria

Iron deficiency anemia is diagnosed when:

• Hemoglobin is below the lower limit of normal for the relevant population (<12 g/dL for women, <13 g/dL for men) 1, 2
• Serum ferritin is <45 ng/mL (AGA recommended cutoff) 1, 2
• Transferrin saturation is <20% 2

Additional laboratory findings may include:

• Elevated total iron binding capacity (TIBC)
• Low serum iron
• Microcytic, hypochromic red blood cells

Initial Workup

1. Laboratory testing:

   • Complete blood count
   • Serum ferritin
   • Transferrin saturation
   • Serum iron and TIBC

2. Screening for celiac disease:

   • Serological testing (found in 3-5% of IDA cases) 1
   • Small bowel biopsy at time of gastroscopy if serology positive

3. Urinalysis/urine microscopy to rule out hematuria 1

4. Endoscopic evaluation:

   • Bidirectional endoscopy (gastroscopy and colonoscopy) for:
     • Men with IDA
     • Postmenopausal women with IDA
     • Premenopausal women with IDA not explained by menstrual blood loss 1
   • CT colonography is a reasonable alternative for those not suitable for colonoscopy 1

Treatment Algorithm

1. First-line treatment: Oral iron supplementation

   • Ferrous sulfate 324 mg (65 mg elemental iron) daily or on alternate days 2, 3, 4
   • Continue for 3 months after normalization of iron parameters to fully replenish stores 2
   • Take on empty stomach or with vitamin C to enhance absorption
   • Common side effects: constipation, nausea, abdominal discomfort

2. For patients with oral iron intolerance or poor response:

   • Try alternate oral preparations (ferrous gluconate, ferrous fumarate)
   • Consider alternate-day dosing to improve absorption and reduce side effects
   • If still intolerant or poor response, consider IV iron 2, 5

3. Intravenous iron indications:

   • Intolerance to oral preparations
   • Malabsorption conditions (celiac disease, post-bariatric surgery)
   • Active inflammatory bowel disease
   • Need for rapid iron repletion
   • Chronic kidney disease 2, 4

Monitoring Response to Treatment

• Check hemoglobin after 2-4 weeks of treatment (good response: Hb rise ≥10 g/L within 2 weeks) 1, 2
• Check ferritin and transferrin saturation after 4-8 weeks of treatment
• Target values: ferritin >30 μg/L and transferrin saturation >16% 2
• Continue monitoring iron parameters every three months for one year after normalization 2

Special Considerations

• Premenopausal women: If heavy menstrual bleeding is the likely cause, gynecological evaluation may be needed
• Persistent or recurrent IDA: Consider small bowel evaluation (capsule endoscopy) if bidirectional endoscopy is negative 1
• Inflammatory conditions: Higher ferritin cutoffs may be needed for diagnosis as ferritin is an acute phase reactant 1, 2
• Pregnant women: Higher iron requirements; may need 30-120 mg/day oral iron supplements 2

Pitfalls to Avoid

1. Inadequate investigation: Failure to investigate the underlying cause of IDA, especially in men and postmenopausal women where GI malignancy is a concern
2. Premature cessation of therapy: Iron therapy should continue for 3 months after normalization of parameters
3. Misinterpreting ferritin levels: Ferritin is an acute phase reactant and may be falsely normal in inflammatory states
4. Overlooking celiac disease: Always screen for celiac disease in patients with IDA
5. Checking iron studies too soon after IV iron: Wait at least 4 weeks after IV iron administration before rechecking iron studies 1

By following this systematic approach to diagnosis and treatment, iron deficiency anemia can be effectively managed while identifying and addressing the underlying cause.