What is the interpretation of iron studies in a patient with anemia (iron deficiency)?

From the Guidelines

Iron studies interpretation in a patient with anemia involves evaluating serum iron, total iron-binding capacity (TIBC), and ferritin levels to determine the underlying cause of the anemia 1, 2, 3, 4, 5.

Key Findings

• A low serum iron level (<50 μg/dL) and low ferritin level (<30 ng/mL) indicate iron deficiency anemia, which may be treated with oral iron supplementation, such as ferrous sulfate 325 mg three times daily for 3-6 months 2.
• In the presence of inflammation, a serum ferritin level up to 100 mg/L may still be consistent with iron deficiency 2, 3, 4.
• A high ferritin level (>200 ng/mL) and normal or elevated serum iron level may suggest anemia of chronic disease, which may require treatment with erythropoiesis-stimulating agents, such as epoetin alfa 10,000 units subcutaneously weekly for 4-6 weeks.

Diagnostic Criteria

• Iron deficiency anemia: serum ferritin < 30 mg/L, transferrin saturation < 16% 4.
• Anemia of chronic disease: serum ferritin > 100 mg/L, transferrin saturation < 16% 4.
• Mixed anemia: serum ferritin between 30 and 100 mg/L 2, 3, 4.

Treatment

• Oral iron supplementation: ferrous sulfate 325 mg three times daily for 3-6 months 2.
• Intravenous iron: may be considered as first-line treatment in patients with clinically active IBD, with previous intolerance to oral iron, with hemoglobin below 100 g/L, and in patients who need erythropoiesis-stimulating agents 2, 3.

From the FDA Drug Label

Evaluate the iron status in all patients before and during treatment. Administer supplemental iron therapy when serum ferritin is less than 100 mcg/L or when serum transferrin saturation is less than 20%.

The interpretation of iron studies in a patient with anemia (iron deficiency) involves evaluating the iron status by checking serum ferritin and serum transferrin saturation levels.

• Serum ferritin should be greater than 100 mcg/L.
• Serum transferrin saturation should be greater than 20%. If these levels are below the recommended thresholds, supplemental iron therapy should be administered 6.

From the Research

Interpretation of Iron Studies

The interpretation of iron studies in a patient with anemia (iron deficiency) is crucial for diagnosis and treatment. The following points highlight the key aspects of iron studies:

• Ferritin measurement is the most important analysis in the study of iron deficiency, but there is no consensus on the diagnostic cut-off 7.
• A ferritin level of < 12-20 μg/L is commonly used, but increasing the diagnostic cut-off to 30 μg/L can significantly improve sensitivity with only a small reduction in specificity 7.
• The ferritin level increases with inflammation and should be considered in conjunction with the CRP level 7.
• Transferrin receptor measurement can be a useful supplement to ferritin measurement, as it increases with iron deficiency without being influenced by inflammation 7, 8.

Differentiating Iron Deficiency Anemia from Anemia of Chronic Disease

Iron deficiency anemia and anemia of chronic disease are two common causes of anemia, and distinguishing between them is essential for diagnosis and treatment. The following points highlight the key differences:

• Serum iron, TIBC, and serum ferritin can be used to diagnose iron deficiency anemia, but these tests have limitations in differentiating it from anemia of chronic disease 9, 10.
• The mean corpuscular volume (MCV) has strong predictive value in differentiating between iron deficiency anemia and anemia of chronic disease, with an MCV of 75 microns3 or less indicating iron deficiency anemia 10.
• Soluble transferrin receptor (sTfR) concentration can be used to diagnose and differentiate iron deficiency anemia from anemia of chronic disease, with a high sensitivity and specificity for iron deficiency anemia 8.

Clinical Application

In clinical practice, iron studies should be interpreted in the context of the patient's clinical presentation and other laboratory results. The following points highlight the key aspects of clinical application:

• Iron deficiency anemia is a common cause of anemia, particularly in females and in developing countries 11.
• Serum ferritin concentration can be used to confirm the diagnosis of iron deficiency anemia, with a low level indicating iron deficiency 11.
• A combination of iron studies, including ferritin, transferrin receptor, and MCV, can be used to diagnose and differentiate iron deficiency anemia from anemia of chronic disease 7, 8, 10.