Which iron study results indicate a need for intravenous (IV) iron therapy, specifically iron sucrose (iron sucrose)?

IV Iron Therapy Recommendation Based on Iron Studies

Option C (Ferritin 1000 µg/L & TSAT 15%) is the correct answer where IV iron therapy should be recommended.

Rationale for Decision

The key principle is that TSAT <20% indicates functional iron deficiency regardless of ferritin level, and this is the primary indication for IV iron therapy, particularly when ferritin is elevated due to inflammation 1.

Analysis of Each Option:

Option A: Ferritin 400 µg/L & TSAT 25%

• TSAT is above the 20% threshold
• This represents iron-replete status
• Not indicated for IV iron 1

Option B: Ferritin 300 µg/L & TSAT 70%

• TSAT is markedly elevated (>50%)
• This indicates iron overload risk
• Contraindicated for IV iron - therapy should be withheld when TSAT ≥50% 1

Option C: Ferritin 1000 µg/L & TSAT 15% ✓

• TSAT <20% indicates functional iron deficiency
• Despite elevated ferritin, the low TSAT demonstrates inadequate iron availability for erythropoiesis
• This is a clear indication for IV iron therapy 1
• The DRIVE study specifically demonstrated benefit in patients with ferritin 500-1200 ng/mL and TSAT <25%, showing significant hemoglobin increases with IV iron 1

Option D: Ferritin 800 µg/L & TSAT 60%

• TSAT >50% indicates iron overload
• Contraindicated for IV iron 1

Clinical Context for Functional Iron Deficiency

Functional iron deficiency occurs when:

• Ferritin is between 30-800 ng/mL (or even >800 ng/mL in inflammatory states)
• TSAT is <20% (most critical parameter)
• Iron stores exist but are sequestered and unavailable for erythropoiesis 1

Evidence Supporting Treatment at High Ferritin with Low TSAT:

The landmark DRIVE study randomized 134 hemodialysis patients with ferritin 500-1200 ng/mL and TSAT <25% to IV ferric gluconate versus no iron 1. Results showed:

• Hemoglobin increased significantly more with IV iron (16±13 vs 11±14 g/L; P=0.028)
• Baseline ferritin was NOT predictive of iron responsiveness
• TSAT <20% remained the key indicator for treatment benefit 1

Important Clinical Pitfalls

⚠️ Do not withhold IV iron based solely on elevated ferritin - in inflammatory conditions (cancer, CKD, chronic disease), ferritin is an acute phase reactant and does not accurately reflect iron availability 1

⚠️ TSAT <20% has high sensitivity (>90%) for diagnosing functional iron deficiency, while ferritin <100 ng/mL has only 35-48% sensitivity in inflammatory states 1

⚠️ Withhold IV iron when TSAT ≥50% to avoid iron overload complications 1

⚠️ Monitor for hypersensitivity reactions - patients should be observed for at least 30 minutes post-infusion with resuscitation equipment available 1

Treatment Approach for Option C

For a patient with ferritin 1000 µg/L and TSAT 15%:

1. Administer IV iron (iron sucrose 100 mg weekly or ferric gluconate 125 mg weekly) 2, 3
2. Consider adding erythropoiesis-stimulating agent (ESA) if anemic, as combination therapy is more effective than either alone for functional iron deficiency 1, 2
3. Recheck iron parameters 4-8 weeks after completing iron therapy 1
4. Expect hemoglobin increase of 1-2 g/dL within 4-8 weeks 1, 2