From the Guidelines
Elevated Mean Corpuscular Volume (MCV) is primarily caused by macrocytic anemias, vitamin deficiencies, and certain medications or conditions, with the most common causes including vitamin B12 and folate deficiencies, as indicated by the European Consensus on the diagnosis and management of iron deficiency and anaemia in inflammatory bowel diseases 1. The causes of elevated MCV can be broken down into several categories, including:
- Macrocytic anemias, which are characterized by larger than normal red blood cells
- Vitamin deficiencies, such as vitamin B12 and folate deficiencies, which impair DNA synthesis and lead to larger red blood cells 1
- Certain medications, such as methotrexate, which can interfere with DNA synthesis and cause macrocytosis, as recommended by the British Association of Dermatologists' guidelines for the safe and effective prescribing of methotrexate for skin disease 2016 1
- Conditions like alcoholism, liver disease, and hypothyroidism, which can also elevate MCV
- Reticulocytosis, or an increase in immature red blood cells, which can naturally elevate MCV
- Laboratory errors, such as prolonged storage of blood samples before testing, which can artificially increase MCV values When elevated MCV is detected, further testing, including vitamin B12 and folate levels, liver function tests, thyroid studies, and possibly bone marrow examination, may be necessary to determine the underlying cause, as suggested by the European Consensus on the diagnosis and management of iron deficiency and anaemia in inflammatory bowel diseases 1.
From the Research
Causes of Elevated MCV
Elevated Mean Corpuscular Volume (MCV) is a condition where the average volume of red blood cells is higher than normal. The causes of elevated MCV can be classified into several categories:
- Megaloblastic anemia, which is caused by deficiency or impaired utilization of vitamin B12 and/or folate 2
- Nonmegaloblastic macrocytic anemia, which is caused by various diseases such as:
- Vitamin B12 deficiency, which can lead to neurological deficits and is associated with an increased MCV 3, 4, 5, 6
- Folate deficiency, which can also cause elevated MCV 4, 5
Association with Other Conditions
Elevated MCV has been associated with several other conditions, including:
- Multiple sclerosis, where patients may have low serum vitamin B12 and folate levels and high levels of homocysteine 6
- Pregnancy, where an MCV cutoff of 93.1 can correctly identify abnormal vitamin B12 levels with 81% sensitivity and 77% specificity 3
- Aging, where the prevalence of macrocytic anemia may increase due to the growing older population 2
Diagnostic Value of MCV
The diagnostic value of MCV in detecting vitamin B12 deficiency is limited, with a sensitivity of 17-77% depending on the population studied 4. Therefore, MCV should not be used as the only parameter to rule out vitamin B12 deficiency, and further evaluation is necessary to confirm the diagnosis.