What is the workup for anemia with low Mean Corpuscular Volume (MCV)?

From the Guidelines

For a workup of anemia with low MCV, start with a complete blood count (CBC) with differential, peripheral blood smear, iron studies (serum iron, total iron-binding capacity, ferritin), and hemoglobin electrophoresis, as recommended by the most recent guidelines 1. The initial evaluation should focus on identifying the underlying cause of the microcytic anemia.

• Iron studies, including serum iron, total iron-binding capacity (TIBC), and ferritin, are crucial in diagnosing iron deficiency anemia, which is a common cause of microcytic anemia 1.
• A low serum iron, high TIBC, and low ferritin suggest iron deficiency anemia, and if confirmed, oral iron supplementation with ferrous sulfate 325 mg three times daily can be initiated 1.
• Hemoglobin electrophoresis is essential to rule out thalassemia, especially if the patient has a family history or is of Mediterranean, African, or Southeast Asian descent, as thalassemia can also cause microcytic anemia 1.
• If iron studies and hemoglobin electrophoresis are normal, consider anemia of chronic disease, and check inflammatory markers like C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) 1. While awaiting test results, take a detailed history focusing on potential causes of blood loss, dietary habits, and any chronic medical conditions, and perform a physical examination looking for signs of systemic disease or occult bleeding 1. This approach allows for a comprehensive evaluation of the most common causes of microcytic anemia, and the history and physical exam can provide valuable clues to the underlying etiology and guide further investigation if needed. The most recent guidelines from 2021 1 provide the best evidence for the workup of anemia with low MCV, and should be followed to ensure the best possible outcomes in terms of morbidity, mortality, and quality of life.

From the Research

Workup for Anemia with Low Mean Corpuscular Volume (MCV)

The workup for anemia with low MCV, also known as microcytic anemia, involves several steps to determine the underlying cause.

• The initial step is to confirm the presence of microcytic anemia by measuring the MCV, which is typically less than 83 micron^3 2.
• The next step is to evaluate iron status by measuring serum ferritin, iron concentration, transferrin saturation, and iron-binding capacity 2, 3.
• Other tests that may be useful in the workup of microcytic anemia include:
  • Serum transferrin receptors to assess tissue iron deficiency 3
  • Erythrocyte zinc protoporphyrin to assess iron-deficient erythropoiesis 3
  • Percentage of hypochromic erythrocytes to assess iron-deficient erythropoiesis 3
  • Reticulocyte haemoglobin concentration to assess iron-deficient erythropoiesis 3
• A complete blood count (CBC) with reticulocyte count and examination of the peripheral smear may also be helpful in evaluating microcytic anemia 4.
• In some cases, additional tests such as hemoglobin electrophoresis or erythrocyte size-distribution width may be necessary to distinguish between different causes of microcytic anemia, such as iron deficiency or thalassemia minor 2, 4.

Key Laboratory Tests

The following laboratory tests are essential in the workup of anemia with low MCV:

• Serum ferritin to assess iron stores 5, 2, 3, 6
• Serum iron and total iron-binding capacity to assess iron status 2, 3, 6
• CBC with reticulocyte count and examination of the peripheral smear to evaluate microcytic anemia 5, 4
• Serum transferrin receptors to assess tissue iron deficiency 3

Importance of Comprehensive Evaluation

A comprehensive evaluation, including measurement of iron status and CBC, is crucial in diagnosing and managing microcytic anemia 5, 6. Relying solely on CBC measures without examining indicators of iron status may lead to misdiagnosis or delayed diagnosis of iron deficiency anemia 6.