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 (with a diagnostic cutoff of 45 ng/mL), transferrin saturation, complete blood count, and screening for celiac disease, followed by bidirectional endoscopy in men and postmenopausal women to exclude gastrointestinal malignancy. 1

Diagnostic Approach

Laboratory Testing

• First-line tests:

  • Complete blood count (CBC) with hemoglobin, hematocrit, MCV, RDW
  • Serum ferritin (primary diagnostic marker)
    • Cutoff of 45 ng/mL is recommended by the American Gastroenterological Association 1
  • Transferrin saturation (<20% suggests iron deficiency) 2
  • Additional tests in equivocal cases:
    • Serum iron
    • Total iron binding capacity (TIBC)

• Diagnostic criteria:

  • Anemia: Hemoglobin below lower limit of normal for the laboratory 1
  • Iron deficiency: Serum ferritin <45 ng/mL 1
  • In inflammatory conditions: May need additional markers as ferritin can be falsely elevated 1, 2

Response to Treatment as Diagnostic Tool

• A good response to iron therapy (Hb rise ≥10 g/L within 2 weeks) is highly suggestive of iron deficiency, even with equivocal iron studies 1

Gastrointestinal Evaluation

Initial Evaluation

• Screening for celiac disease:

  • Serologic testing (first-line approach)
  • Small bowel biopsy only if serology positive 1
  • Found in 3-5% of IDA cases 1

• Endoscopic evaluation:

  • Men and postmenopausal women: Bidirectional endoscopy (gastroscopy and colonoscopy) is strongly recommended 1
  • Premenopausal women: Bidirectional endoscopy is conditionally recommended 1
  • Alternative: CT colonography for those unsuitable for colonoscopy 1

• H. pylori testing:

  • Non-invasive testing for H. pylori, with treatment if positive 1

Further Evaluation (if initial workup negative)

• For patients with negative bidirectional endoscopy and inadequate response to iron therapy or recurrent IDA:
  • Small bowel evaluation (capsule endoscopy preferred) 1
  • Renal tract evaluation 1

Treatment

Oral Iron Therapy

• First-line treatment:

  • Oral iron supplementation with 60-120 mg elemental iron daily 1, 2
  • Common preparations:
    • Ferrous sulfate 325 mg (65 mg elemental iron)
    • Ferrous gluconate 300 mg (37 mg elemental iron)
    • Ferrous fumarate 210 mg (69 mg elemental iron) 2

• Dosing schedule:

  • Traditional approach: Divided into 2-3 doses daily 2
  • Alternative approach: Once daily or every other day dosing may improve tolerance 3
  • Add vitamin C to enhance absorption if response is poor 2

Parenteral Iron Therapy

• Indications:

  • Intolerance to oral iron preparations
  • Malabsorption conditions
  • Continued blood loss
  • Inflammatory conditions
  • Chronic kidney disease 2, 4

• Monitoring response:

  • Check hemoglobin after 3-4 weeks of treatment
  • Expected response: Hemoglobin rise of approximately 2 g/dL
  • Hemoglobin increase of at least 1.0 g/dL at day 14 predicts adequate response 2

Special Populations

Pregnant Women

• Screening: At first prenatal visit 1
• Treatment: 60-120 mg/day elemental iron 1
• Referral: If Hb <9.0 g/dL or Hct <27.0%, refer to specialist 1
• Dose adjustment: When Hb normalizes, decrease to 30 mg/day 1

Chronic Inflammatory Conditions

• May require IV iron therapy due to impaired oral absorption 2, 5
• Inflammatory bowel disease patients often benefit from parenteral iron 5

Common Pitfalls to Avoid

• Inadequate diagnostic workup (missing underlying cause)
• Premature discontinuation of therapy before iron stores replenished
• Overlooking celiac disease as a cause
• Inappropriate use of parenteral iron when oral therapy would suffice
• Inadequate follow-up of treatment response
• Misinterpreting lab values in the context of inflammation 2

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