How should I manage a patient with iron deficiency anemia based on these lab results?

Interpretation and Management of Iron Studies

These labs show functional iron deficiency (low TIBC and low UIBC despite normal serum iron and transferrin saturation), which requires investigation for underlying causes and consideration of iron supplementation based on clinical context.

Lab Interpretation

Your patient's iron studies reveal:

• Serum Iron: 64 µg/dL (normal) - within reference range 1
• UIBC: 129 µg/dL (LOW) - below normal range of 155-355 1
• Transferrin Saturation: 33.2% (normal) - within 20-50% range 1
• TIBC: 193 µg/dL (LOW) - significantly below normal range of 250-450 1

This pattern suggests functional iron deficiency or anemia of chronic disease/inflammation rather than absolute iron deficiency. The low TIBC with normal transferrin saturation is atypical for classic iron deficiency anemia, where TIBC is typically elevated 1.

Clinical Context Assessment

Determine if anemia is present:

• Check hemoglobin level - anemia is defined as Hb <130 g/L in men or <120 g/L in non-pregnant women 1
• If anemic, the urgency increases: men with Hb <120 g/L and postmenopausal women with Hb <100 g/L warrant more urgent investigation 1

Assess for inflammation or chronic disease:

• Measure serum ferritin - this is the single most useful marker for iron deficiency 1
  • Ferritin <15 µg/L confirms absolute iron deficiency 1
  • Ferritin <45 µg/L suggests iron deficiency in most contexts 1
  • Ferritin <100 ng/mL with inflammation indicates iron deficiency 2
  • Ferritin >100 µg/L makes absolute iron deficiency unlikely 1
• Check inflammatory markers (CRP, ESR) - ferritin is an acute phase reactant and may be falsely elevated with inflammation 1

Investigation Strategy

For patients WITH anemia:

Bidirectional endoscopy is recommended for men and postmenopausal women to exclude gastrointestinal malignancy, as GI blood loss is the most common cause in these populations 1, 3. This includes:

• Upper endoscopy (gastroscopy) with duodenal biopsies 1
• Colonoscopy 1

Celiac disease screening should be performed with tissue transglutaminase (tTG) antibody testing 1, 3. If positive, confirm with small bowel biopsy 1.

Premenopausal women <40 years without red flags may not require bidirectional endoscopy if menstrual blood loss is the likely cause 3.

For patients WITHOUT anemia (non-anemic iron deficiency):

GI investigation is generally not warranted in premenopausal women without other concerning features, as menorrhagia is the likely cause 1. However, investigation should be considered if there are additional risk factors or symptoms 1.

Treatment Approach

Oral Iron Supplementation (First-line):

Ferrous sulfate 325 mg (65 mg elemental iron) daily is the standard treatment 4, 2. Key points:

• Every-other-day dosing improves absorption and reduces side effects 2
• Treatment duration: typically 3-6 months to normalize hemoglobin and replenish stores 3
• Reassess in 2-4 weeks - expect Hb rise ≥10 g/L within 2 weeks if true iron deficiency 1, 2
• Approximately 50% of patients experience adverse effects affecting adherence 2

Intravenous Iron (Second-line or specific indications):

Consider IV iron if 2, 5, 3:

• Intolerance to oral iron
• Inadequate response to oral therapy after 2-4 weeks
• Malabsorption (celiac disease, inflammatory bowel disease, post-bariatric surgery)
• Heart failure (IV iron improves exercise capacity) 1, 2
• Chronic kidney disease with ESA therapy 1

In CKD patients on dialysis, higher ferritin targets (>200 ng/mL) and transferrin saturation >20% reduce ESA requirements 1. IV iron can be beneficial even with ferritin 500-1200 ng/mL if transferrin saturation <25% 1.

Common Pitfalls to Avoid

• Do not assume dietary deficiency alone - always investigate for GI pathology in men and postmenopausal women 1
• Do not rely solely on transferrin saturation when ferritin is unavailable - it has limited specificity 1, 5
• Do not over-supplement iron - excessive supplementation can cause iron overload, especially in hereditary hemochromatosis 6, 7
• Do not ignore dual pathology - 1-10% of patients have bleeding sources in both upper and lower GI tracts 1
• Do not forget to stop NSAIDs if being used, as they are common causes of occult GI bleeding 1