What is the diagnosis of iron deficiency based on serum ferritin levels?

From the Guidelines

Iron deficiency should be diagnosed based on serum ferritin levels, with a threshold of <45 ng/mL indicating iron deficiency, as recommended by the American Gastroenterological Association (AGA) 1.

Key Points to Consider

• In patients with underlying inflammation or chronic kidney disease, additional laboratory tests may be needed to confirm iron deficiency.
• The use of a cut-off of 45 ng/mL over 15 ng/mL when using ferritin to diagnose iron deficiency is recommended by the AGA 1.
• Bidirectional endoscopy is recommended for asymptomatic postmenopausal women and men with iron deficiency anemia, while for asymptomatic premenopausal women, bidirectional endoscopy is suggested over iron replacement therapy only 1.

Interpretation of Serum Ferritin Levels

• Serum ferritin levels below 45 ng/mL indicate iron deficiency.
• In the presence of inflammation, a higher threshold (such as <100 ng/mL) may be used to diagnose iron deficiency.
• Additional tests like transferrin saturation (<16%), serum iron, or soluble transferrin receptor may be needed to confirm iron deficiency.

Treatment and Investigation

• Treatment typically involves oral iron supplementation (ferrous sulfate 325 mg 1-3 times daily, providing 65 mg elemental iron per tablet) for 3-6 months to replenish stores.
• For those who cannot tolerate oral iron due to gastrointestinal side effects, intravenous iron formulations like iron sucrose or ferric carboxymaltose may be used.
• The underlying cause of iron deficiency should always be investigated, particularly in men and postmenopausal women where gastrointestinal blood loss is a common cause.

From the Research

Iron Deficiency Calculator Based on Serum Ferritin

• Iron deficiency is a common cause of morbidity and can arise as a consequence or complication from many diseases 2.
• The diagnosis of iron deficiency is typically made by measuring serum ferritin levels, with a level of <30 ng/mL indicating iron deficiency in individuals without inflammatory conditions 3.
• Serum ferritin levels can be used to calculate the severity of iron deficiency, with lower levels indicating more severe deficiency.
• The following factors can be used to calculate iron deficiency based on serum ferritin:
  • Serum ferritin level (<30 ng/mL)
  • Presence of inflammatory conditions
  • Presence of anemia
  • Symptoms such as fatigue, pica, or restless legs syndrome
• A study published in the European Journal of Heart Failure recommends defining iron deficiency in patients with heart failure as a transferrin saturation (TSAT) <20% and a serum ferritin level <400 μg/L 4.
• Another study published in JAMA states that iron deficiency is diagnosed by low serum ferritin (typically <30 ng/mL) in individuals without inflammatory conditions or by transferrin saturation (iron/total iron binding capacity × 100) less than 20% 3.
• It is essential to note that the calculation of iron deficiency based on serum ferritin levels may vary depending on the individual's clinical context and the presence of underlying conditions.

Key Considerations

• The use of intravenous iron preparations is indicated for the treatment of iron deficiency when oral preparations are ineffective or cannot be used 2.
• Oral iron supplementation is typically the first-line treatment for iron deficiency anemia, with daily doses between 80 mg and 200 mg of elemental iron 5.
• The choice of iron supplement and dosage may depend on the individual's specific needs and medical history.
• Regular monitoring of serum ferritin levels and other iron parameters is necessary to assess the effectiveness of iron supplementation and adjust treatment as needed.

Clinical Applications

• Iron deficiency calculators based on serum ferritin levels can be useful tools for healthcare professionals to diagnose and manage iron deficiency in various clinical contexts.
• These calculators can help identify individuals at risk of iron deficiency and guide treatment decisions, including the choice of iron supplement and dosage.
• However, it is crucial to consider the individual's clinical context and medical history when using these calculators to ensure accurate diagnosis and effective treatment.