What is the appropriate management for an adult patient with iron deficiency anemia, as indicated by laboratory values of low ferritin, iron, and iron saturation, and high total iron-binding capacity?

Management of Iron Deficiency Based on Laboratory Values

These laboratory values (ferritin 41 ng/mL, transferrin saturation 9%, serum iron 35 μg/dL, TIBC 386 μg/dL) confirm iron deficiency and require both iron replacement therapy and investigation to identify the underlying cause, particularly evaluation for gastrointestinal pathology in men and postmenopausal women. 1

Interpretation of Laboratory Values

Your patient's iron studies definitively indicate iron deficiency:

• Ferritin 41 ng/mL: This falls below the 45 μg/L threshold that provides optimal sensitivity and specificity for iron deficiency (specificity 0.92), and is well below the 150 μg/L level that would exclude absolute iron deficiency even with inflammation 1

• Transferrin saturation 9%: This is markedly low (normal >20%), confirming inadequate iron availability for erythropoiesis 1, 2

• Elevated TIBC 386 μg/dL: The raised total iron-binding capacity is characteristic of iron deficiency 1

• Low serum iron 35 μg/dL: Consistent with depleted iron stores 1

Immediate Clinical Actions Required

1. Determine Hemoglobin Level

Check the hemoglobin immediately if not already done, as this determines urgency of investigation and treatment approach 1:

• Men with Hb <110 g/L or postmenopausal women with Hb <100 g/L: Warrant fast-track referral for urgent gastrointestinal evaluation 1
• Any level of anemia with iron deficiency: Should be investigated, with stronger indication for more severe anemia due to higher likelihood of serious GI pathology 1

2. Initiate Iron Replacement Therapy

Start oral iron supplementation immediately while pursuing diagnostic workup 1, 2:

• Ferrous sulfate 324 mg daily (containing 65 mg elemental iron) is a reasonable first-line choice 3, 2
• Alternative dosing: 325 mg daily or on alternate days (alternate-day dosing may improve tolerability) 2
• Administration: Take on empty stomach for optimal absorption; if not tolerated, may take with meals (preferably with meat protein and 500 mg vitamin C to enhance absorption) 1
• Expected response: Hemoglobin should rise ≥10 g/L within 2 weeks if true iron deficiency 1

3. Mandatory Diagnostic Evaluation

The following investigations are essential to identify the source of iron deficiency 1:

History and Physical Examination

Focus on specific high-yield elements 1:

• Dietary history: Assess iron intake adequacy
• Medication review: NSAIDs, aspirin, anticoagulants 1
• Bleeding history: Menstrual blood loss (premenopausal women), hematochezia, melena, hematuria
• GI symptoms: Dyspepsia, dysphagia, change in bowel habits, abdominal pain
• Risk factors: Family history of GI malignancy, previous GI surgery, inflammatory bowel disease

Laboratory Testing

• Urinalysis or urine microscopy: To exclude urinary tract bleeding 1
• Celiac disease screening: Tissue transglutaminase (tTG) antibody testing, as celiac disease is found in 3-5% of IDA cases 1
• Complete blood count with indices: Assess MCV, MCH for microcytosis/hypochromia 1

Endoscopic Evaluation

For men and postmenopausal women with newly diagnosed iron deficiency 1:

• Bidirectional endoscopy (gastroscopy and colonoscopy) should be first-line GI investigation 1
• Gastroscopy with duodenal biopsies: Even if celiac serology is negative, obtain biopsies if there are other features suggesting celiac disease (though not routinely required if tTG negative) 1
• CT colonography: Reasonable alternative if colonoscopy not suitable 1
• Rationale: Approximately one-third of men and postmenopausal women with IDA have underlying GI pathology, including malignancy 1

For premenopausal women 1:

• GI investigation generally not warranted if menorrhagia or recent pregnancy explains iron deficiency and there are no GI symptoms or family history of GI malignancy 1
• Lower threshold for investigation if: GI symptoms present, family history of GI cancer, or persistent iron deficiency despite adequate iron replacement 1

Special Considerations and Pitfalls

When to Consider Intravenous Iron

IV iron is indicated over oral iron in the following situations 1, 4, 2:

• Intolerance to oral iron (nausea, abdominal pain, constipation)
• Malabsorption conditions (celiac disease, inflammatory bowel disease, post-bariatric surgery) 1
• Ongoing blood loss that cannot be immediately controlled
• Chronic inflammatory conditions (chronic kidney disease, heart failure, inflammatory bowel disease, cancer) where oral absorption is impaired 1, 2
• Pregnancy (second and third trimesters) 1, 2
• Failure to respond to oral iron after 4-6 weeks of adequate therapy 4

Monitoring Response to Therapy

Reassess hemoglobin after 2-4 weeks of iron therapy 1:

• Expected response: Hb rise ≥10 g/L within 2 weeks is highly suggestive of absolute iron deficiency 1
• If no response: Consider malabsorption, continued bleeding, incorrect diagnosis, or non-adherence 5
• Continue iron therapy: For 3-6 months after hemoglobin normalizes to replenish iron stores 6, 2

Common Pitfalls to Avoid

• Do not delay investigation pending response to iron therapy in men or postmenopausal women, as this may miss GI malignancy 1
• Do not assume dietary deficiency alone without excluding pathologic causes, especially in men and postmenopausal women 1
• Do not overlook celiac disease screening, as it is present in 3-5% of IDA cases and requires specific management 1
• Do not interpret ferritin in isolation if inflammatory conditions are present; ferritin up to 100 μg/L may still reflect iron deficiency in the setting of inflammation 1