MCV - Mean corpuscular volume: normal, high and low values

MCV

What does MCV mean?

 What is MCV? MCV is the English acronym for mean corpuscular volume, in Italian mean globular volume or mean globular value. It is a parameter found in the blood count that indicates the average value of the volume of red blood cells, or erythrocytes.

It is important not to confuse the mean cell volume with the MPV analysis, which instead stands for Mean platelet volume: this parameter gives us information on the average volume of our platelets and certainly helps us to understand how healthy and efficient is hematopoiesis (the synthesis of all blood cells, including leukocytes and platelets), but not from specific information on erythrocytes.

THE normal values of MCV oscillate between 80 and 100 femtoliters. MCV values below 80 fl indicate a microcytosis of red blood cells, also called microcythemia: that is, small red blood cells will be produced. Conversely, values greater than 100 µl describe a condition of macrocytosis of red blood cells (hence large red blood cells).

The value of the MCV it is useful in the diagnosis of anemia, since some of them are associated with microcytosis and others with macrocytosis. Furthermore, to make a more precise diagnosis of anemia, it is useful to look at other parameters indicated in the blood count, such as:

  • Hemoglobin or Hb: protein contained exclusively in Red blood cells which acts as an oxygen carrier. Physiological values range between 12-16 g / dL for women and 13-17 g / dL in men. The finding of low hemoglobin is an indication of anemia, and is typically associated with low erythrocytes.
  • Red blood cells or RBCs, in Italian erythrocytes or red blood cells): indicates the amount of red blood cells present in the blood. A condition of low erythrocytes indicates anemia and is obviously associated with a drop in hemoglobin levels, the latter being contained in erythrocytes. Physiological values are 4.52 - 5.90 x1012 per liter (men) and 4.10 - 5.10 x1012 per liter (women). However, blood tests can reveal high erythrocytes: high red blood cell values, in which case they are labeled as erythrocytosis. Low red blood cells can also underlie possible bleeding.
  • Hematocrit or htc: the percentage of blood volume occupied by the corpuscular elements, ie the blood cells. Blood is made up of a liquid part (the plasma) and a part made up of cells (red blood cells, white blood cells ...). An increase in the hematocrit describes hemoconcentration: this occurs when the number of red blood cells is increased due to certain diseases, or when the liquid component of the blood is reduced. The hematocrit is decreased in case of anemia, as the amount of red blood cells is reduced.
  • MCH: Content cell average of Hemoglobin. Indicates the mass average hemoglobin contained in a single erythrocyte. Low MCV and MCH they are often associated; in this case we are in the presence of hypochromic and microcytic anemia. The term hypochromic indicates low MCH e derives from the fact that the reduced hemoglobin content alters the color of the red cells under the microscope: the red blood cells have a biconcave disc appearance with the central area lighter and, in the case of hypochromia, this light is increased, since the amount of hemoglobin, which gives RBCs their red color. Conversely, a High MCH it reads like hyperchromia. Therefore High MCV and MCHon the contrary, they define hyperchromic macrocytic anemia.
  • MCHC: Concentration cellular average of hemoglobin. This parameter depends on the relationship between the quantity of hemoglobin and from volume of erythrocytes. Conditions that alter the morphology of red blood cells modify this parameter. An example is spherocytosis, for example, in which red blood cells are spherical in shape rather than discoid. Blood tests will reveal MCHC high in case of microcytosis (since, even in the presence of a normal hemoglobin content, it will be more "concentrated" as the erythrocytes are smaller) and Low MCHC in the presence of macrocytosis.
  • RDW o amplitude of the erythrocyte distribution: it is a parameter that gives information on diameter mean of red blood cells and is expressed as a percentage ratio. It is useful for discriminating different anemias that present themselves as microcytic: ferropriva anemia and thalassemia, for example, both result in the production of small red blood cells (microcytes), but the RDW value is different. A high RDW indicates, in summary, that in the blood we have a majority percentage of erythrocytes all of the same size, associated with a minority percentage of smaller or larger red blood cells.

Low MCV

From these parameters it is clear that the blood count is a fundamental exam, in hematology but also in general medicine, to evaluate some aspects of our health. Let us now examine the alterations of the globular value and the possible causes.

What does it mean to have low MCV? MCV is considered low if i values are less than 80 fl. If the hemoglobin values are also low, we are in the presence of microcytic anemia.

Causes of low MCV

Some examples of microcytic anemia I'm:

Chronic disease anemia (e.g. in the presence of renal insufficiency);

Iron deficiency anemia;

Thalassemia (genetic disease causing altered hemoglobin production);

Sideroblastic anemia (Defective production of a component of hemoglobin, the heme group, results in the production of altered red blood cells, called sideroblasts ring, due to their characteristic appearance under the microscope).

Other causes of low to medium corpuscular volume can be:

- Vitamin B6 deficiency;

- Rheumatoid arthritis;

- Lead poisoning;

- Cooley's disease;

The most frequent cause of microcytosis in the population is certainly low iron or hyposideremia:

We get a certain amount of iron in our diet every day; our body also has a considerable reserve of iron (about 3-4 g), distributed variously between the liver, spleen, bone marrow and red blood cells (in the latter case linked to a specific component of hemoglobin called heme group). A progressive consumption of these deposits, or any other loss of iron (as occurs for example for women with a heavy menstrual cycle) over the long term depletes the body's reserve. The resulting anemia is due to the fact that iron is essential for the correct synthesis of red blood cells and is the fundamental constituent of hemoglobin; if it fails, there will consequently be a progressive decrease in the number of erythrocytes, up to anemia.

Causes of iron deficiency:

  1. Reduced food intake (diet low in meat and legumes);
  2. Insufficient absorption of dietary iron (frequent in some diseases of the gastrointestinal tract);
  3. Excessive blood loss (bleeding; menstruation);
  4. Increased need not compensated by adequate supplementation (for example in pregnancy).

Low MCV remedies and therapy

 How to lower the mcv? The answer is not complicated: as we have seen, low MCV definitely indicates microcytic anemia, so treatment will aim to treat the latter. In case of iron deficiency anemia, the first step is certainly iron supplements (with the diet, but also pharmacological). In case of severe anemia, with very low hemoglobin levels, support with transfusions is very important. Controlling the underlying disease (eg kidney failure, vitamin deficiency, rheumatoid arthritis) will also have benefits on microcytic anemia.

High MCV

What does it mean to have high MCV? MCV values are considered high if above 100 fl and indicate a condition of macrocytosis. High MCV-associated anemia is macrocytic anemia.

Causes of high MCV

The most frequent cause of macrocytic anemia is deficiency of vitamin B12 and folic acid or folate, very important substances for the correct maturation of erythrocytes. Our body has a reserve of these elements, but dietary intake and their correct absorption in the gastrointestinal tract are essential.

The shortage of B12 is folate cause megaloblastic anemia. The defective absorption of B12 due to stomach affections (fundamental since it produces the intrinsic factor, without which the absorption of of the vitamin does not occur) causes instead pernicious anemia.

 

Hemolytic anemia is also associated with macrocytosis: in this case there is an excessive breakdown of red blood cells. Hemolysis can occur in the circulation (due to poisons, incompatible transfusions, or mechanical causes, such as the presence of artificial heart valves or in the case of patients undergoing hemodialysis), and in this case it is intravascular; but it can also be the work of the spleen, the organ typically responsible for hemocateresis. In the latter case, hemolytic anemia is caused by the production of abnormal red blood cells (as occurs in the case of thalassemia, spherocytosis or sickle cell anemia), which are therefore a doubled burden on the spleen.

Other causes of medium-high corpuscular volume:

- Alcoholism;

- Hypothyroidism;

- Liver disease;

- Bone marrow diseases such as aplastic anemia (in which there is a functional insufficiency of the marrow which will affect not only red blood cells, but also white blood cells and platelets) and myelodysplastic syndrome (in which the synthesis of corpuscular elements exists, but it is faulty).

How to lower the MCV

Since the latter is an indicative parameter of an underlying enemy state, the first step to regularizing it will be to treat anemia. In case this is due to folate and B12 deficiencies, an adequate diet accompanied by supplements will bring benefits in the long term. In the case of the other causes mentioned above, therapy will be based on thyroid hormone compensation, on the treatment of liver disease or medullary aplasia.

Symptoms of high and low MCV

Symptoms of high or low MCV are related to the underlying anemia, plus any manifestations of underlying disease (liver or gastrointestinal disease, chronic kidney disease, rheumatoid arthritis, etc.)

Typical symptoms of anemia are:

- Easy fatigue;

- Sense of weakness (asthenia);

- Palpitations and tachycardia;

- headache;

- Neuromuscular pains;

- Pallor;

- Chest pain;

- Dyspnea (feeling of shortness of breath) from exertion.

Why is the MCV measured: indications for the exam

As we have seen, the mean globular volume is a parameter now routinely measured on the blood count, because it allows us to identify the possible cause of anemia more precisely. Consequently, in the presence of the aforementioned symptoms (or, in general, a clinical suspicion of anemia) the first step will be a complete blood count, the first examination that any doctor prescribes to his patient, whether it is a first approach or a control. .

Preparation and Factors Affecting Measurement

 In view of the sampling for the evaluation of the mean globular volume it is essential to observe a fasting period of at least 8 hours. The age of the patient may affect the measurement (elderly patients are more likely to have a high MCV in the absence of precise causes).

CVD and pregnancy

Pregnancy is a beautiful and delicate period for the female body: pregnant women are particularly exposed to folate, B12 and iron deficiency, because the intake of these elements takes into account not only the mother's needs, but also that of the fetus. With the same dietary intake and in the presence of normal reserves, consumption has practically doubled. For this reason, the risk of developing ferrous (microcytic) or B12 and folate deficiency (macrocytic) anemia is increased. The blood tests, with the parameters mentioned above, will be accompanied by a martial attitude (sideremia and serum ferritin), B12 and folic acid, for a prompt and accurate diagnosis.

In light of the above, it is essential for pregnant women to prevent iron and B12 deficiency with an adequate diet (especially meat, eggs, milk and legumes and vegetables high in iron and vitamins, such as spinach) and, if necessary, with supplements.

MCV and sport

Athletes, especially those involved in high-level sports, are also more at risk of developing anemia, particularly iron deficiency.

One of the causes can be the increase in gastrointestinal losses, especially frequent in long-lasting endurance sports, such as walking or marathon. Iron deficiency negatively affects athletic performance, as it leads to reduced hemoglobin production. The latter is essential for the transport of oxygen to the tissues; as a result, fatigue increases, especially in the case of aerobic activity.

MCV in children

 CVD values in children are important in identifying the origin of anemia. In fact, as also for adults, the anemic state could be due to an increased destruction of red blood cells, an increase in losses (haemorrhages) and a reduced synthesis. The latter must be investigated thoroughly, to exclude primary pathologies of the marrow or hemoglobinopathies.

 

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