MCV In A Blood Test: What Is It, Decoding, Norms, Deviations

2024 Author: Rachel Wainwright | [email protected]. Last modified: 2023-12-15 07:39

MCV in a blood test - what is it?

The content of the article:

1. Red blood cells and their function in the body
2. Normal MCV Values
3. Reasons for increasing MCV
4. MCV in the blood test is lowered
5. How is MCV blood test done

MCV (mean corpuscular volume) is one of the erythrocyte indices, which shows the average volume of erythrocytes. This indicator is able to characterize the entire population of red blood cells in the blood. The calculated measure denotes the average volume that one erythrocyte takes. The value of this index is calculated by the formula: hematocrit as a percentage, multiplied by 10 and divided by the total number of red blood cells in the blood. In most laboratories, MCV is measured in cubic microns (μm2) or femtoliters (fl).

The MCV index determines the average volume of red blood cells

A change in the erythrocyte composition of the blood is one of the main laboratory criteria in the diagnosis of anemia, therefore, the calculation of the average volume of erythrocytes in combination with other indicators of the clinical blood test is used for differential diagnosis, monitoring and evaluation of the effectiveness of treatment of anemia and diseases of the hematopoietic system, determination of violations of the water-electrolyte balance.

Red blood cells and their function in the body

Erythrocytes are red blood cells that contain hemoglobin. Their main function is to transport oxygen and carbon monoxide between the lungs and tissues of other organs. In addition, erythrocytes are involved in the reactions of the immune system, play a significant role in maintaining the acid-base balance, serve as a means of transporting nutrients (glucose, amino acids, salts, fatty acids) and decay products (uric acid, urea, ammonia, creatine).

Red blood cells form in the bone marrow. Their life cycle is 120 days, after which the erythrocytes are metabolized by the cells of the liver, spleen and bone marrow. They are being replaced by young forms of red blood cells called reticulocytes. Before entering the microvasculature, cells go through several stages of development, during which their shape, size and chemical composition change. For the normal synthesis of red blood cells, a sufficient intake of vitamin B12, iron and folic acid is necessary.

Mature erythrocytes are non-nuclear cells that have the shape of biconcave discs, which allows them to penetrate into the narrowest and most curved sections of the vascular bed. Due to the plasticity of erythrocytes, the viscosity of blood in small capillaries is much lower than in large ones.

The average diameter of a red blood cell in an adult is between 6.8 and 7.5 microns. Red blood cells with a diameter of less than 6.8 microns are called microcytes, and a condition in which the size of peripheral blood red blood cells is much less than normal means the presence of microcytosis. The presence in the blood of abnormally large, with a diameter of more than 8 microns, erythrocytes (macrocytes) makes it possible to suspect macrocytosis in the patient.

The indicator of the average volume of erythrocytes has diagnostic value in assessing micro- and macrocytosis, it is used in calculating the average content and concentration of hemoglobin in erythrocytes.

Normal MCV Values

The norm of MCV in the blood test varies depending on age: in newborns it is maximum, in children in the first days and months of life, its range is somewhat wider than in adults, after a year the indicator decreases, and by the age of 18 it is fixed at a level of 80 to 100 fl. This means that with age, the level of the average volume of red blood cells becomes lower. For men and women, the MCV rate and the interpretation of the blood test will also be different. In addition, the norms of blood parameters may differ depending on the method of determination, laboratory, units of measurement.

Normal MCV values by gender and age

Age	MCV, fl
0-1 day	Girls - up to 128 fl Boys - up to 128 fl
1 Week	Girls - up to 100 fl Boys - up to 100 fl
1 week to 1 year	Girls - 77-79 fl Boys - 77-79 fl
1-2 years	Girls - 72-89 fl Boys - 70-90 fl
3-6 years old	Girls - 76-90 fl Boys - 76-89 fl
7-12 years old	Girls - 76-91 fl Boys - 76-81 fl
13-16 years old	Girls - 79-93 fl Boys - 79-92 fl
20-29 years old	Women - 82-96 fl Men - 81-93 fl
30-39 years old	Women - 91-98 fl Men - 80-93 fl
40-49 years old	Women - 80-100 fl Men 81-94 fl
50-59 years old	Women - 82-99 fl Men - 82-94 fl
60-65 years old	Women 80-100 fl Men - 81-100 fl
65 and older	Women - 80-99 fl Men - 78-103 fl

An increase or decrease in the MCV index in the general blood test may indicate various diseases and pathological conditions, for example, a violation of the water-salt balance: with a decrease in the average volume of erythrocytes, the disorders are hypertensive, and with an increase, they are hypotonic.

Reasons for increasing MCV

An increase in MCV in the blood may indicate a lack of vitamin B12, a lack of folic acid, the development of hyperchromic or macrocytic anemia, myelodysplastic syndrome, pathologies of the liver, bone marrow, renal failure, myxedema, hypothyroidism. The indicator of the average volume of red blood cells can be increased in case of methanol poisoning, alcohol abuse, smoking, and taking certain medications.

A false overestimation of the average volume of erythrocytes can occur with hyperglycemia and diabetic ketoacidosis, cold agglutination of erythrocytes.

Deviations of the MCV index from the norm in one direction or another can serve as an indicator of different types of anemia.

MCV in the blood test is lowered

The MCV index can be lowered in the case of microcytic anemia (iron deficiency, sideroblastic), hypochromic anemia with a lack of hemoglobin, thalassemia, with renal diseases that increase the level of erythropoietin, hypertensive dehydration, blood loss, conditions accompanied by impaired formation or increased destruction of the liver with tissue changes, erythremia, hypothyroidism, cancer and autoimmune diseases. The average volume of red blood cells often decreases during pregnancy in women who are iron deficient. The reason for the reduced rate may be lead poisoning, mechanical hemolysis, the presence of giant platelets.

To confirm or refute the diagnosis, additional studies are prescribed: a biochemical blood test, determination of hormone levels, detection of tumor markers, immunological tests, ultrasound and others.

How is MCV blood test done

Determination of the erythrocyte index is performed as part of a general blood test, but it can also be prescribed as a separate study.

Blood sampling is performed on an empty stomach, after an overnight fasting period of at least eight, and preferably ten to twelve hours. On the eve of the analysis, it is recommended to refrain from excessive physical and psycho-emotional stress, to exclude physiotherapy procedures.

MCV in a blood test is calculated automatically - using a hematological analyzer, which determines the average volume of all measured red blood cells. The manual calculation method, in which the laboratory assistant himself counts the cells and makes calculations according to the formula, is rarely used.

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Anna Kozlova Medical journalist About the author

Education: Rostov State Medical University, specialty "General Medicine".

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