From the Guidelines
When both MCV and MCHC are low, the most critical labs to order include a complete blood count (CBC) with peripheral smear, iron studies (serum iron, total iron binding capacity, ferritin), and hemoglobin electrophoresis, as these tests help differentiate between iron deficiency anemia and thalassemia, which are the most likely causes of these lab abnormalities.
Key Labs to Order
- Complete blood count (CBC) with peripheral smear to assess red blood cell morphology and detect any abnormalities
- Iron studies, including serum iron, total iron binding capacity, and ferritin, to diagnose iron deficiency anemia, with ferritin being the most sensitive marker 1
- Hemoglobin electrophoresis to identify thalassemias, which can present with similar lab abnormalities
- Reticulocyte count to assess bone marrow response
- Vitamin B12 and folate levels to rule out other nutritional anemias that might coexist
Additional Testing
In certain cases, additional testing may be necessary, such as:
- Lead levels, especially in children 1
- Inflammatory markers like CRP or ESR if chronic disease is suspected
- Stool occult blood tests to identify potential gastrointestinal bleeding sources These comprehensive tests allow for accurate diagnosis and appropriate treatment planning for the underlying cause of the microcytic, hypochromic anemia indicated by low MCV and MCHC values. It is essential to consider the clinical context and potential inflammatory conditions that may affect ferritin levels, as noted in the British Society of Gastroenterology guidelines 1.
From the Research
Low MCV and MCHC Diagnosis
When MCV and MCHC are low, it is essential to order labs that can help diagnose the underlying cause of microcytic anemia.
- The most common cause of microcytic anemia is iron deficiency, as stated in the study 2.
- To diagnose iron deficiency, the following labs can be ordered:
- Serum ferritin: This is the most definitive test for iron deficiency, as it measures the amount of iron stored in the body 2.
- Iron concentration: This measures the amount of iron in the blood.
- Transferrin saturation: This measures the percentage of transferrin that is saturated with iron.
- Iron-binding capacity: This measures the amount of transferrin that is available to bind to iron.
- Serum transferrin receptors: This can help differentiate between iron deficiency and other microcytic states 2.
- Other labs that can be ordered to rule out other causes of microcytic anemia include:
- Hemoglobin electrophoresis: This can help diagnose thalassemia and other hemoglobinopathies.
- Reticulocyte count: This can help diagnose sideroblastic anemia and other disorders of iron metabolism.
- It is essential to note that normal values of MCV, MCH, and MCHC do not exclude empty iron stores in anemic patients, as stated in the study 3.
- The study 3 also found that MCH was slightly more accurate than MCV and MCHC in diagnosing empty iron stores.