What labs are used to work up microcytic anemia?

From the Guidelines

The initial laboratory workup for microcytic anemia should include a complete blood count (CBC) with red cell indices, peripheral blood smear, reticulocyte count, serum iron studies (serum iron, total iron binding capacity, transferrin saturation, and ferritin), and hemoglobin electrophoresis. This recommendation is based on the most recent and highest quality study available, which emphasizes the importance of a comprehensive laboratory workup in diagnosing microcytic anemia 1. The following tests are essential in the initial workup:

• Complete blood count (CBC) with red cell indices
• Peripheral blood smear
• Reticulocyte count
• Serum iron studies (serum iron, total iron binding capacity, transferrin saturation, and ferritin)
• Hemoglobin electrophoresis Additional tests to consider are:
• Lead levels (especially in children)
• Soluble transferrin receptor levels
• Inflammatory markers like C-reactive protein or erythrocyte sedimentation rate In cases where the diagnosis remains unclear, a bone marrow examination may be necessary, particularly for suspected sideroblastic anemia, where bone marrow examination with iron staining is essential 1. Specific testing for hereditary conditions such as thalassemia should include hemoglobin electrophoresis and potentially genetic testing. The pattern of results, particularly the red cell distribution width (RDW), mean corpuscular volume (MCV), and iron studies, provides valuable diagnostic information to guide appropriate treatment strategies, as highlighted in the study published in Gut in 2021 1. It is also important to note that serum ferritin concentration is the most powerful test for iron deficiency, and a level of <15 μg/L is indicative of absent iron stores, while levels of less than 30 μg/L are generally indicative of low body iron stores 1. However, serum ferritin may be raised above 12–15 μg/dl in patients with iron deficiency and concurrent chronic inflammation, malignancy, or hepatic disease. Therefore, a comprehensive approach to laboratory testing is necessary to accurately diagnose and manage microcytic anemia.

From the Research

Laboratory Tests for Microcytic Anemia

To work up microcytic anemia, several laboratory tests can be used, including:

• Complete blood count (CBC) to determine the mean corpuscular volume (MCV) and confirm the presence of microcytic anemia 2
• Serum ferritin measurement to diagnose iron deficiency anemia, as low ferritin levels suggest iron deficiency 3, 4
• Total iron-binding capacity, transferrin saturation level, and serum iron level to differentiate between iron deficiency anemia and other microcytic anemias 3, 4, 2
• Hemoglobin electrophoresis to diagnose thalassemia and other hemoglobinopathies 3, 4, 2
• Reticulocyte count to evaluate the bone marrow's response to anemia 2

Diagnostic Approach

The diagnostic approach to microcytic anemia involves:

• Categorizing the anemia as microcytic, macrocytic, or normocytic based on the MCV 2
• Examining the peripheral smear to confirm the diagnosis 2
• Using specific tests, such as serum iron level, total iron-binding capacity, and hemoglobin electrophoresis, to separate the microcytic anemias 2
• Evaluating the erythrocyte size-distribution width to distinguish iron deficiency from thalassemia minor 2

Common Causes of Microcytic Anemia

The most common causes of microcytic anemia are:

• Iron deficiency anemia, which is the most common type of microcytic anemia 5, 3, 4
• Thalassemia, which is a genetic disorder that affects the production of hemoglobin 3, 4, 2
• Anemia of chronic disease, which is characterized by low iron levels and decreased total iron-binding capacity 4
• Sideroblastic anemia, which is a rare disorder that affects the production of hemoglobin 5