What are the laboratory findings for Iron Deficiency Anemia (IDA)?

From the Guidelines

Iron deficiency anemia should be diagnosed using a combination of laboratory tests, including a complete blood count (CBC), serum ferritin, serum iron, total iron binding capacity (TIBC), and transferrin saturation, with serum ferritin being the most sensitive test for iron deficiency, as recommended by the British Society of Gastroenterology guidelines 1.

Key Laboratory Tests

• Complete blood count (CBC) to evaluate hemoglobin, hematocrit, and red blood cell indices
• Serum ferritin to assess iron stores, with levels below 30 ng/mL strongly suggesting iron deficiency
• Serum iron and TIBC to evaluate iron availability, with decreased serum iron and increased TIBC indicating iron deficiency
• Transferrin saturation to assess the percentage of transferrin saturated with iron, with levels typically <15% in iron deficiency anemia

Interpretation of Laboratory Results

• A low hemoglobin level (typically <13 g/dL in men and <12 g/dL in women) and microcytic hypochromic red blood cells on the CBC suggest iron deficiency anemia
• Serum ferritin levels below 30 ng/mL confirm iron deficiency, while levels above 100 ng/mL may indicate inflammation or other conditions 1
• Transferrin saturation <20% has high sensitivity for diagnosing absolute or functional iron deficiency, but ferritin levels <100 ng/mL have low sensitivity in patients with inflammatory conditions 1

Additional Tests

• Reticulocyte count to evaluate bone marrow response, which may be low or normal despite anemia
• Peripheral blood smear to evaluate red blood cell morphology, which may show microcytic hypochromic red cells with anisocytosis and poikilocytosis
• Soluble transferrin receptor (sTfR) and reticulocyte hemoglobin content (CHr) or reticulocyte hemoglobin equivalent (RET-He) may be useful in certain situations, such as inflammation or thalassemia, but are not routinely available 1

From the Research

Iron Deficiency Anemia Labs

• The diagnosis of iron deficiency anemia can be challenging due to the cost of ferritin tests, leading physicians to consider alternative methods such as complete blood count (CBC) parameters 2.
• A study found that CBC parameters, including red blood cell (RBC) count, hematocrit, mean corpuscular volume (MCV), mean corpuscular hemoglobin concentration (MCHC), and mean corpuscular hemoglobin (MCH), can be used to diagnose iron deficiency anemia with varying degrees of accuracy 2.
• The study found that a hematocrit cutoff value of 38.5% had low discriminating power in diagnosing iron deficiency only, but five parameters had higher discriminating powers for iron deficiency anemia: RBC count, MCV, MCHC, MCH, and hematocrit 2.
• Another study found that serum ferritin radioimmunoassay is a powerful test for the diagnosis of iron-deficiency anemia, with an area under the receiver operating characteristic curve of 0.95 3.
• The study also found that test properties differed for populations of patients with inflammatory, liver, or neoplastic disease and patients without these conditions, and that likelihood ratio lines can be used to interpret results across the entire range of ferritin concentration values 3.

Laboratory Tests

• Serum ferritin radioimmunoassay is considered a highly accurate test for diagnosing iron-deficiency anemia 3.
• CBC parameters, including RBC count, hematocrit, MCV, MCHC, and MCH, can also be used to diagnose iron deficiency anemia, but with lower accuracy than serum ferritin radioimmunoassay 2.
• The choice of laboratory test may depend on the patient population and the presence of underlying conditions such as inflammation, liver disease, or neoplasia 3.

Note

• One study was not relevant to the topic of iron deficiency anemia labs, as it discussed the total condylar knee prosthesis and its use in knee deformities 4.