From the Guidelines
When hemoglobin levels are normal but MCV and MCHC are low, this likely indicates microcytic hypochromic red blood cells with compensatory mechanisms maintaining adequate hemoglobin, and the most common possibility is iron deficiency in its early stages. This condition is characterized by microcytosis, which is a mean corpuscular volume (MCV) lower than the normal range, as noted in the guidelines for the management of iron deficiency anaemia by the British Society of Gastroenterology 1. The presence of low MCHC further supports this diagnosis, as it indicates that the red blood cells have a lower than normal concentration of hemoglobin.
According to the study by the British Society of Gastroenterology 1, serum ferritin concentration is the most powerful test for iron deficiency, and a serum ferritin concentration of <12 μg/dl is diagnostic of iron deficiency. However, other possibilities such as thalassemia minor, anemia of chronic disease, or sideroblastic anemia should also be considered.
Key points to consider in this diagnosis include:
- Microcytosis may be absent in combined deficiency, such as with folate deficiency, which may be recognized by a raised red cell distribution width (RDW) 1
- The anaemia of chronic disease due to the inability to use iron may also present with microcytosis 1
- Haemoglobinopathies frequently cause microcytosis in certain ethnic groups, but this should not be presumed to be the cause unless confirmed by laboratory testing 1
Further testing is recommended to confirm the diagnosis, including serum iron, ferritin, total iron binding capacity, and hemoglobin electrophoresis. For suspected iron deficiency, oral iron supplementation may be prescribed while awaiting test results.
From the Research
Significance of Normal Hemoglobin with Low MCV and MCHC
- Normal hemoglobin levels with low Mean Corpuscular Volume (MCV) and Mean Corpuscular Hemoglobin Concentration (MCHC) can indicate microcytic anemia, which is defined as anemia with an MCV of less than 80 mcm3 in adults 2.
- The most common cause of microcytic anemia is iron deficiency anemia, which can be managed with oral or intravenous iron, depending on the severity and comorbid conditions of the affected individual 2, 3.
- Other causes of microcytic anemia include thalassemia, sickle cell anemia, and sideroblastic anemia, which can be identified through further testing and evaluation 2, 4.
- A low MCV and MCHC can also be indicative of iron depletion, which can quickly develop into iron deficiency anemia if not detected early 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
- Hematological parameters such as hematocrit, Hb, MCV, MCH, MCHC, and red blood cell distribution width (RDW) can be useful in differentiating between different types of microcytic anemia, including iron deficiency anemia and alpha-thalassemia 4.
- Genomic DNA testing and measurement of serum ferritin can also be used to diagnose and differentiate between these conditions 4.
- It is essential to consider the age, sex, and race of the individual when interpreting hemoglobin levels and MCV, as normal ranges can vary 3.