From the Guidelines
To diagnose iron deficiency anemia, a complete blood count (CBC), serum ferritin, serum iron, total iron-binding capacity (TIBC), and transferrin saturation should be ordered, as these tests collectively provide a comprehensive assessment of iron status and help differentiate iron deficiency anemia from other microcytic anemias. The CBC is essential as it will show decreased hemoglobin, hematocrit, and mean corpuscular volume (MCV), indicating a microcytic anemia 1. Serum ferritin is the most specific test for iron stores and is typically low (<30 ng/mL) in iron deficiency, with levels less than 15 μg/L confirming iron deficiency 1. Additional iron studies should include serum iron (decreased), total iron-binding capacity (TIBC, increased), and transferrin saturation (decreased, usually <15%) 1. In unclear cases, soluble transferrin receptor levels may be helpful as they increase with iron deficiency but remain normal in anemia of chronic disease 1. Hemoglobin electrophoresis might be necessary to rule out thalassemias, which can present similarly 1. It's also important to consider the patient's inflammatory status, as chronic inflammation can affect iron metabolism and ferritin levels, making diagnosis more complex 1. The most recent and highest quality study, from 2020, recommends measuring serum ferritin levels to diagnose iron deficiency anemia, with levels less than 15 μg/L confirming iron deficiency 1. Therefore, based on the strongest and most recent evidence, ordering a CBC, serum ferritin, serum iron, TIBC, and transferrin saturation is the most appropriate approach to diagnose iron deficiency anemia.
From the Research
Labs to Check for Iron Deficiency Anemia
To diagnose iron deficiency anemia, several laboratory tests can be utilized. These include:
- Complete Blood Count (CBC) parameters such as:
- Red Blood Cell (RBC) count
- Hematocrit levels
- Mean Corpuscular Volume (MCV)
- Mean Corpuscular Hemoglobin Concentration (MCHC)
- Mean Corpuscular Hemoglobin (MCH) 2
- Serum ferritin levels, which is the preferred initial diagnostic test 3, 4
- Transferrin saturation (iron/total iron binding capacity × 100) 3
- Reticulocyte Hemoglobin Content (CHr), which can be used for diagnosis and monitoring of iron therapy 5
- Total iron-binding capacity, serum iron, and serum transferrin receptor levels may be helpful in certain cases 4
Diagnostic Criteria
Iron deficiency is typically defined as a serum ferritin level <30 ng/mL in individuals without inflammatory conditions 3. Iron deficiency anemia is defined as a ferritin level <30 µg/L with a hemoglobin level <120 g/L 2.
Special Considerations
In pregnant women, a hemoglobin concentration of less than 11.0 g/dL in the first trimester and less than 10.5 or 11.0 g/dL in the second or third trimester is considered anemia 6. The American College of Obstetricians and Gynecologists recommends screening for anemia with a complete blood count in the first trimester and again at 24 0/7 to 28 6/7 weeks of gestation 6.