What is Mean Corpuscular Volume?
The term “mean corpuscular volume” (or MCV for short) is a crucial tool for doctors to pinpoint the root cause of anemia, a condition where your body lacks enough healthy red blood cells. MCV is a measurement from a lab test that determines the average size of your red blood cells. This information is important in diagnosing anemia.
Here’s an easier way to explain it – think of MCV like a blueprint of anemia, giving details on the properties of your red blood cells. Alongside other lab values such as hemoglobin and hematocrit (the percentage of your total blood volume that’s made up of red blood cells), MCV can categorize anemia into three main types—microcytic, normocytic, and macrocytic.
Microcytic anemia occurs when MCV levels are below normal, and your red blood cells are smaller than usual. Normocytic anemia is when MCV levels fall within the normal range, and your red blood cells are their standard size. Lastly, macrocytic anemia is when MCV values overshoot the normal range, leading to larger-than-normal red blood cells. This classification is essential because it guides further investigations and helps your doctor to decide the best course of action.
In addition, MCV is used to calculate something called the red blood cell distribution width (RDW) – a measure that depicts the variety in red blood cell size and shape in your blood. This too, provides valuable information for your doctor to diagnose and manage your anemia.
What Causes Mean Corpuscular Volume?
Doctors use a measurement called MCV (Mean Corpuscular Volume) to clearly identify the type of anemia a patient has. There are three types of anemia: microcytic, normocytic, and macrocytic.
Microcytic anemia means that the red blood cells are smaller than usual, and much smaller compared to white cells. On a full blood test, the MCV is below 80 fL (femtoliters), whereas a normal MCV is between 80 and 100 fL. This type of anemia is often linked to long-term iron-deficiency, sideroblastic anemia (a group of blood disorders), and thalassemias (inherited blood disorders), though it can also be a symptom of other conditions. In microcytic anemia, the cells often show a larger clear or pale center, especially when linked to iron-deficiency and long-term disease-related anemia.
Macrocytic anemia describes a situation where the red blood cells are larger than normal, with the MCV measurement exceeding 100 fL on a full blood test. One type of this anemia, megaloblastic anemia, is associated with impaired DNA synthesis, while another type, non-megaloblastic anemia, keeps normal DNA synthesis. Megaloblastic anemia is commonly caused by deficiencies in folate (also known as folic acid or vitamin B9), vitamin B12, or orotic aciduria (a rare genetic disorder that prevents conversion of orotic acid to uridine monophosphate). Non-megaloblastic anemia can result from liver failure, chronic alcoholism, or a rare inherited disease known as Diamond-Blackfan anemia.
Normocytic anemia is when the hemoglobin and hematocrit (a measure of red blood cells in the blood) levels are low, but MCV falls within the normal range of 80 to 100 fL. This type can further be divided into hemolytic or non-hemolytic groups. Normocytic hemolytic anemia can occur within blood vessels, and outside blood vessels due to various underlying causes. Other indicators on a full blood test can help to identify the type of anemia, assisting in diagnosis. Non-hemolytic normocytic anemias may be found in conditions such as early stage anemia due to long-term disease, early iron-deficiency anemia, aplastic anemia (when the body stops producing enough new blood cells), microangiopathic hemolytic anemias (a group of disorders causing red blood cell death) and certain infections caused by plasmodium (parasites that cause diseases such as malaria).
Risk Factors and Frequency for Mean Corpuscular Volume
The MCV (Mean Corpuscular Volume) usually increases as people get older. The pattern of this increase appears to follow two line graphs: the first includes people from 1 to 25 years old, and the second includes those from 26 to 88 years old. It is also observed that women between 40 to 80 years old typically have lower MCV values than men. Age and gender influence these changes in MCV.
Different types of anemia more commonly affect specific demographics. For example, microcytic anemia, which often occurs due to iron deficiency, especially affects menstruating women who do not have adequate iron supplementation. However, in men and postmenopausal women over 50, colorectal cancer could potentially cause this type of anemia, so they should undergo a colonoscopy to rule it out.
- Anemia of chronic disease is another common type of anemia across the globe, which is frequently seen in patients with chronic inflammatory conditions. This leads to irregular iron levels. Anyone can be affected by this type of anemia, regardless of age and gender.
- Sideroblastic anemia can be inherited or acquired, and may be caused by a number of factors including lead exposure, lacking vitamin B6, consuming alcohol chronically, or copper deficiency. It’s crucial to identify these causes to narrow down the diagnosis.
- Myelodysplastic disorders affect roughly 10,000 individuals each year, primarily men over 65.
- Myeloproliferative diseases can be both inherited and acquired.
- Thalassemia, a type of anemia, can either be alpha or beta, and affects different populations. Alpha-thalassemia is commonly seen in African, Southern Chinese, Malaysian, and Thai populations, whereas beta-thalassemia is seen in African and Mediterranean populations.
- Macrocytic anemia is quite common, with a global prevalence that varies from 1.7% to 3.6%. It is caused by deficiencies of folate and vitamin B12, which can affect any demographic, particularly individuals following vegan diets or suffering from certain diseases.
- Diamond-Blackfan anemia is a congenital condition showing up within the first year of life. It affects various races and ethnicities, and the rate of occurrence varies between 1 per 100,000 to 1 per 200,000 live births.
- Lastly, normocytic anemia can be due to a variety of causes and can affect people of all ages, genders, and ethnicities.
Signs and Symptoms of Mean Corpuscular Volume
Mean Corpuscular Volume, or MCV, is a measure used in blood tests. It helps to diagnose different types of anemia, which is a condition characterized by a low count of red blood cells. When the MCV is below 80 fL, it might mean that an individual has iron-deficiency anemia. Symptoms can include pale skin, fatigue, sensitivity to cold, spoon-shaped nails, and dry lips.
People with iron-deficiency anemia often have a history of long-term blood loss or chronic inflammation. Exposure to lead paint or a family history of thalasemia, a blood disorder, could be additional factors. There are also other types of anemia, such as anemia of chronic disease or thalasemias, which come with their own symptoms and can often be traced back to a family history of these conditions or a disease causing chronic inflammation, such as rheumatoid arthritis or cancer.
Iron-deficiency anemia can also be related to certain conditions like endometriosis. However, higher MCV, above 100 fL, can suggest vitamin B12 deficiency, often connected to a vegan diet without supplements or certain medical conditions. Folate deficiency is another possible scenario, particularly risky for pregnant women in term of birth defects. An elevated MCV can also be linked with certain medical conditions, diseases or suggest a higher risk of heart and brain problems, and also give hints related to probability of survival and treatment response in some types of cancer, such as esophageal squamous cell carcinoma.
Mean Corpuscular Volume between 80 and 100 fL can be associated with both intrinsic and extrinsic normocytic anemias, often characterized by darkened urine. The underlying causes might range from malaria to consumption of undercooked ground beef or autoimmune diseases. It is important to remember that these are general pointers and any diagnosis is based on a comprehensive evaluation by a healthcare professional.
Testing for Mean Corpuscular Volume
If you have anemia, a condition where your body doesn’t make enough red blood cells, the doctor will perform a variety of tests to figure out what’s causing it. One of these tests is a complete blood count (CBC) which measures the number of different cells in your blood, including red blood cells, white blood cells, and platelets. Certain features, such as the size of your red blood cells (measured by MCV), can help them identify the type of anemia you might have.
If you’re a woman who has heavy periods (menorrhagia) and your red blood cells are smaller than normal (MCV below 80 fL), they might do tests such as Von Willebrand factor assay and thyroid panel to figure out if your menstrual history could be the cause of your anemia. If you’re over 50 with small red blood cells, they might do a colonoscopy. This test looks at the lining of your large intestine to check for growths (polyps) or cancer, which might be causing you to lose iron and develop anemia.
If your anemia is due to a chronic disease and the exact cause is unclear, the doctor may run some extra tests. These might include looking for signs of rheumatoid arthritis, lupus, or vasculitis in your blood, and testing your kidneys’ function with a urine test. They might also do a CT scan or chest X-ray to check for cancer.
If they think you may have been exposed to lead, they’ll check your blood lead levels. In some cases, if they need to rule out other causes of a type of anemia called sideroblastic anemia, they might need to take a sample of your bone marrow. Tests to check for conditions like β-thalassemia and α-thalassemia, which are genetic blood disorders, might also be done.
If your red blood cells are normal-sized but you don’t have enough of them (normocytic anemia), the doctor may examine your blood and urine under a microscope. If they see broken red blood cells (schistocytes) and hemoglobin in your urine, it could suggest one type of anemia, called microangiopathic hemolytic anemia. But if these aren’t present and they still suspect hemolysis (breakdown of red blood cells), they may further investigate.
In dialysis patients, doctors may monitor the average size of your red blood cells (MCV), especially the younger, larger ones (MCVr), to track recovery from conditions like iron deficiency and megaloblastic anemia.
In cases of macrocytic anemia, where your red blood cells are larger than normal, your doctor will look for potential causes, such as alcoholism, liver failure, or problems with absorbing nutrients from your diet, including lack of vitamin B12 or folate. They may also test your urine for certain substances, like orotic acid and ammonia, if they suspect you have a rare genetic condition called orotic aciduria. Diamond-Blackfan anemia is another rare condition that they’re usually able to diagnose with the information gathered so far, though additional tests might be done to screen for related conditions.
Treatment Options for Mean Corpuscular Volume
Microcytic anemia, a condition where your red blood cells are smaller than normal, is often due to iron deficiency. Women who experience this may be given iron supplements, and in some cases, birth control pills to control menstrual cycles and reduce blood flow. If hypothroidism, a condition where the thyroid gland doesn’t produce enough hormones, is the cause, medication like levothyroxine may be prescribed.
Macrocytic anemia, where red blood cells are larger than normal, is usually treated based on the root causes. Deficiencies of vitamin B12 and folate, a type of Vitamin B, are treated with supplements. People who drink alcohol may be advised to stop and might be given folate supplements. For patients diagnosed with a rare genetic disorder called orotic aciduria, a certain type of enzyme supplement may be needed to restore the normal function.
Normocytic anemia, where red blood cells are normal size but not enough in number, requires different treatments based on the individual’s condition. For instances, a disease called paroxysmal nocturnal hemoglobinuria may be treated with a drug called eculizumab. Severe anemia may require blood transfusions to restore sufficient red blood cell levels. Bone marrow failure may require hematopoietic stem cell transplantation, where healthy stem cells replace the damaged ones.
For those with hemolytic anemia due to conditions like mechanical heart valves or a hardened and narrowed aorta, surgical interventions might be an option. Conditions like malaria or babesiosis, require treatment with suitable medications to effectively handle the infection.
Microangiopathic hemolytic anemia, another type of anemia, may be the result of various health conditions. Treatments might involve procedures like plasmapheresis, where plasma is removed and replaced with fresh one, and drugs including corticosteroids and other medication to reduce flares.
For hereditary spherocytosis, a condition where red blood cells assume a sphere shape making them fragile and prone to breakage, treatments might include supplements, blood transfusions, and vaccinations against bacteria prior to removal of the spleen.
Anemia of chronic disease can be treated by using anti-inflammatory drugs, corticosteroids, and other medication, unless a malignancy or growth is the root cause, which should then undergo standard cancer treatment. For patients with acquired iron overload, iron supplementation is not recommended. Upon suspicion of an infection caused by H. pylori bacterium, further testing may be required.
What else can Mean Corpuscular Volume be?
When diagnosing different types of anemia based on MCV results from a complete blood count (CBC), doctors consider various related conditions; each type of anemia has different possible causes:
For Microcytic anemias (MCV lower than 80 fL), possible causes might include:
- Iron-deficiency anemia
- Anemia of chronic disease
- Sideroblastic anemia
- H pylori infection
- Thalassemias
Macrocytic anemias (MCV greater than 100 fL) can be megaloblastic or non-megaloblastic in nature. Some of the possible causes include:
- Folate deficiency due to chronic alcoholism, certain drugs, or intestinal malabsorption/resection
- Vitamin B12 deficiency due to intestinal diseases, strict vegan diets, or certain types of anemia
- Conditions leading to liver disease or insufficiency
When it comes to Normocytic anemias (MCV between 80 and 100 fL), the potential causes can be related to various forms of hemolytic or aplastic anemias. Possible conditions include:
- Intravascular hemolytic anemia caused by paroxysmal nocturnal hemoglobinuria or problems with certain clotting conditions
- Extravascular hemolytic anemia caused by hereditary conditions, certain infections, or autoimmune diseases
- Aplastic anemia which could be related to certain genetic disorders, exposure to radiation or harmful substances, various infections, and certain types of leukemia
What to expect with Mean Corpuscular Volume
Anemia, or low blood count, can have outcomes that change based on different factors. Here is a general view of different types of anemia and the likely results:
Iron-deficiency anemia generally improves with iron supplements. However, if it’s due to having a chronic disease like cancer, the outlook gets worse, and it can even be fatal. Anemia caused by chronic diseases depends on the specific disease. For example, anemia caused by cancer isn’t as easily treated as anemia from arthritis.
Sideroblastic anemia is usually mild and can be treated with supplements or by avoiding what’s causing it. But, thalassemias, a group of inherited blood disorders, have varying outlooks. β-thalassemia major, one type of thalassemia, is most severe. However, with ongoing blood transfusions and iron decrease treatment, people with this condition can live normal lives. However, life expectancy is still reduced due to the risk of other diseases.
Folate and cobalamin deficiencies, which result in a type of anemia called megaloblastic anemia, usually have a good outlook with proper supplements. But vitamin B12 deficiency can be deadly if it leads to severe neurological issues, though it can be prevented with appropriate supplementation. Folate deficiency is not usually serious, unless the patient is pregnant. In that case, it can be serious for the unborn child.
People with orotic aciduria and Diamond-Blackfan anemia can have a good outlook if they regularly take medicine. If they don’t, their condition can cause serious problems, even death. Anemias caused by chronic alcoholism can have a poor outlook, as these individuals often have many vitamin deficiencies that can lead to brain damage, liver failure and other severe health problems.
Normocytic anemias, which means the red blood cells are normal size but low in number, often have a poor outlook due to ongoing blood cell destruction. However, with new treatments, the outcome can improve. Diseases causing destruction of red blood cells outside of the bloodstream, such as sickle cell disease, generally have a poor outlook with a life expectancy in the range of 30-40 years. These patients may suffer from painful episodes due to blockages in their blood vessels, which can be fatal.
Possible Complications When Diagnosed with Mean Corpuscular Volume
Anemia with varying MCV often results in increased mortality and complications if left untreated. People with iron-deficiency anemia, without iron supplementation, can develop severe heart problems. Lead poisoning is also dangerous and potentially fatal if not treated with chelation therapy and by removing the source of lead toxicity.
Untreated systemic lupus erythematosus, a type of autoimmune disease, can cause problems with kidney function, which is typically the leading cause of death among these patients. β-thalassemia major patients often experience complications from treatment, such as acquired hemochromatosis. These patients specifically need ongoing chelation therapy, or else they face the risk of death due to iron intoxication and severe heart complications.
In pregnant people, folate deficiency can cause neural tube defects in the developing fetus. A deficiency in vitamin B12 may cause nervous system disorders. Lack of the proper supplements for conditions like orotic aciduria and Diamond-Blackfan anemia can be deadly.
People with liver insufficiency or cirrhosis can face a wide range of complications:
- Hyperammonemia (too much ammonia in the blood)
- Ascites (fluid build-up in the abdomen)
- Portal hypertension (high blood pressure in the liver)
- Cardiomegaly (enlarged heart)
- Esophageal varices with potential rupture and bleeding
- Internal hemorrhoids
- Hepatorenal syndrome (kidney failure due to liver disease)
- Hepatic encephalopathy (confusion and coma due to liver failure)
Chronic alcoholism can lead to these complications through alcoholic cirrhosis, along with a syndrome known as Wernicke-Korsakoff syndrome due to thiamine deficiency. People with normocytic anemia can experience various complications like bloody urine, fainting, skin spots, high fevers, and death. Providing timely and effective treatment is essential to prevent these potential complications and improve patient outcomes.
Preventing Mean Corpuscular Volume
The Mean Corpuscular Volume (MCV), which is a measurement of the average size of your red blood cells, is an important part of identifying what kind of anemia you might have, and understanding your risk of heart-related issues. However, MCV alone might not give a full picture of what’s happening, particularly in patients who have both small (microcytic) and large (macrocytic) red blood cells. That’s why doctors usually take a detailed approach. This involves looking at your medical history, doing a physical checkup, and examining results from a Complete Blood Count (CBC) test – a blood test that counts your red and white blood cells and your platelets. This way, doctors don’t rely solely on MCV but use additional crucial details to assess your state of health.
