From the Guidelines
Low MCV is not only indicated for ferritin deficiency, as it can be caused by several conditions beyond iron deficiency, including thalassemia, anemia of chronic disease, and sideroblastic anemia. According to the study published in the Journal of the National Comprehensive Cancer Network 1, microcytic anemia (MCV < 80 fL) can be caused by iron deficiency, thalassemia, anemia of chronic disease, and sideroblastic anemia. While ferritin levels are an important indicator of iron deficiency, a low MCV requires a comprehensive evaluation to determine the underlying cause.
Some key points to consider when evaluating a patient with low MCV include:
- Iron deficiency: low ferritin levels, low transferrin saturation, and elevated total iron binding capacity 1
- Thalassemia: normal ferritin levels, very low MCV relative to the degree of anemia, and abnormal hemoglobin electrophoresis results
- Anemia of chronic disease: low ferritin levels, elevated inflammatory markers, and a normocytic or microcytic anemia
- Sideroblastic anemia: presence of sideroblasts in bone marrow biopsy and abnormal iron studies
A thorough evaluation of a patient with low MCV should include a complete blood count with peripheral smear, iron studies, inflammatory markers, and in some cases, lead levels or hemoglobin electrophoresis to determine the underlying cause of the microcytosis. The diagnosis and treatment of low MCV should be guided by the underlying cause, rather than solely relying on ferritin levels.
From the Research
Low MCV Indications
- Low MCV is not only indicated for ferritin, but also for other conditions such as thalassemia, anemia of chronic disease, lead toxicity, and sideroblastic anemia 2, 3, 4, 5.
- Iron deficiency anemia is the most common cause of microcytic anemia, which is characterized by a low MCV 2, 3, 4, 5.
- A low MCV can be an indication of iron deficiency anemia, but it can also be caused by other factors, and serum ferritin measurement is the first laboratory test recommended in the evaluation of microcytosis 4, 5.
- The combined use of serum ferritin and MCV measurements can help distinguish between iron deficiency, beta-thalassemia trait, and normal subjects with an accuracy of over 95% 6.
Diagnostic Considerations
- Serum ferritin level is the best single laboratory parameter for the diagnosis of iron deficiency 5.
- If the serum ferritin level is not initially low, further evaluation should include total iron-binding capacity, transferrin saturation level, serum iron level, and possibly hemoglobin electrophoresis 4.
- Anemia of chronic disease is suggested with low iron levels and decreased total iron-binding capacity 4.
- Patients with beta-thalassemia trait usually have elevated levels of hemoglobin A2 4.