What does a percent saturation of 12 and a ferritin level of 81 indicate?

Iron Status Interpretation with Transferrin Saturation 12% and Ferritin 81 ng/mL

A transferrin saturation of 12% with ferritin of 81 ng/mL indicates functional iron deficiency that requires iron supplementation, despite the ferritin level being within normal limits. 1

Understanding the Laboratory Values

When interpreting iron studies, both transferrin saturation (TSAT) and ferritin must be considered together:

• TSAT of 12%: This is significantly below the threshold of 20% that indicates iron deficiency according to clinical guidelines 1
• Ferritin of 81 ng/mL: This falls in a gray zone (30-100 ng/mL) that could represent possible iron deficiency, especially when inflammation is present 2

Clinical Significance

This pattern represents a classic case of functional iron deficiency, where:

• Iron is inadequately available for erythropoiesis despite seemingly adequate stores
• The low TSAT (<20%) indicates poor iron availability for red blood cell production
• The ferritin level (81 ng/mL) suggests some iron stores are present but may be insufficient 1

Recommended Management

1. Iron supplementation is indicated:

   • For adults: Oral iron at a dose of at least 200 mg elemental iron daily 1
   • If oral iron is ineffective or poorly tolerated, consider IV iron therapy

2. Follow-up monitoring:

   • Measure TSAT and ferritin after 4-8 weeks of therapy
   • Target TSAT >20% and ferritin >100 ng/mL 1

3. Further evaluation:

   • Investigate potential causes of iron deficiency (blood loss, malabsorption)
   • Consider testing for chronic inflammation if ferritin seems disproportionately high compared to TSAT

Important Distinctions

Types of Iron Deficiency:

• Absolute iron deficiency: Depleted iron stores (ferritin <12 ng/mL in healthy subjects, <100 ng/mL in chronic kidney disease) 1
• Functional iron deficiency: Inadequate iron availability despite some stores (low TSAT with normal/elevated ferritin) 1

Common Pitfalls to Avoid:

1. Don't rely solely on ferritin: A ferritin of 81 ng/mL might appear normal, but the low TSAT of 12% clearly indicates functional iron deficiency 1, 3

2. Don't overlook inflammation: Ferritin is an acute phase reactant and may be falsely elevated in inflammatory states, masking iron deficiency 1, 4

3. Don't miss the clinical impact: Low TSAT (<20%) is independently associated with increased morbidity and mortality, regardless of ferritin levels 5

Special Considerations

If the patient has chronic kidney disease, heart failure, or is receiving erythropoietin therapy, the iron requirements are higher and IV iron may be more appropriate than oral supplementation 1, 5

For patients with chronic liver disease or inflammatory conditions, the interpretation becomes more complex, and additional testing such as reticulocyte hemoglobin content or soluble transferrin receptor may be helpful 6