Mean corpuscular volume
Encyclopedia
The mean corpuscular volume, or "mean cell volume" (MCV), is a measure of the average red blood cell
size that is reported as part of a standard complete blood count
.
In patients with anemia
, it is the MCV measurement that allows classification as either a microcytic anemia
(MCV below normal range), normocytic anemia
(MCV within normal range) or macrocytic anemia (MCV above normal range).
If the MCV was determined by automated equipment, the result can be compared to RBC morphology on a peripheral blood smear. Any deviation would be indicative of either faulty equipment or technician error.
For further specification, it can be used to calculate red blood cell distribution width
s can increase MCV. In pernicious anemia
(macrocytic), MCV can range up to 150 femtolitre
s. An elevated MCV is also associated with alcoholism
(as are an elevated GGT
and a ratio of AST
:ALT
of 2:1). Vitamin B12
and/or folic acid
deficiency has also been associated with macrocytic anemia (high MCV numbers).
are iron deficiency (due to inadequate diet
ary intake, gastrointestinal blood loss
, or menstrual blood loss
), thalassemia
, or chronic disease. In iron deficiency anemia
(microcytic anemia), it can be as low as 60 to 70 femtolitres. In some cases of thalassemia
, the MCV may be low even though the patient is not iron deficient.
A low MCV number in a patient with a positive stool guaiac test
(bloody stool) is highly suggestive of GI cancer.
Red blood cell
Red blood cells are the most common type of blood cell and the vertebrate organism's principal means of delivering oxygen to the body tissues via the blood flow through the circulatory system...
size that is reported as part of a standard complete blood count
Complete blood count
A complete blood count , also known as full blood count or full blood exam or blood panel, is a test panel requested by a doctor or other medical professional that gives information about the cells in a patient's blood...
.
In patients with anemia
Anemia
Anemia is a decrease in number of red blood cells or less than the normal quantity of hemoglobin in the blood. However, it can include decreased oxygen-binding ability of each hemoglobin molecule due to deformity or lack in numerical development as in some other types of hemoglobin...
, it is the MCV measurement that allows classification as either a microcytic anemia
Microcytic anemia
Microcytic anemia is a generic term for any type of anemia characterized by small red blood cells. The normal mean corpuscular volume is 76-100 fL, with smaller cells as macrocytic....
(MCV below normal range), normocytic anemia
Normocytic Anemia
Normocytic anemia is a common issue that occurs for men and women typically over 85 years old. Its prevalence increases with age, reaching 44 percent in men older than 85 years...
(MCV within normal range) or macrocytic anemia (MCV above normal range).
Methodology And Normal Values
- To calculate the MCV, expressed in femtoliters (fLFemtolitreThe femto litre is the metric unit of volume equal to 10−15 litre, or one quinine cillionth or one quadrillionth litre. It is abbreviated FL or fl. One femto litre is the same as 1 μm3.1....
, or 10-15L), the following formula is used:10 x hematocrit (%) divided by RBC count (millions/mm3). The normal range for MCV is: 80-99 fL. - Use of volume-sensitive automated blood cell counters, such as the Coulter counter. In this type of apparatus, the red cells pass one-by-one through a small aperture and generate a signal directly proportional to their volume.
- Other automated counters measure red blood cell volume by means of techniques that measure refracted, diffracted, or scattered light.
If the MCV was determined by automated equipment, the result can be compared to RBC morphology on a peripheral blood smear. Any deviation would be indicative of either faulty equipment or technician error.
For further specification, it can be used to calculate red blood cell distribution width
Red blood cell distribution width
The red blood cell distribution width is a measure of the variation of red blood cell width that is reported as part of a standard complete blood count. Usually red blood cells are a standard size of about 6–8 μm. Certain disorders, however, cause a significant variation in cell size. Higher...
High
In presence of hemolytic anaemia, presence of reticulocyteReticulocyte
Reticulocytes are immature red blood cells, typically composing about 1% of the red cells in the human body.Reticulocytes develop and mature in the red bone marrow and then circulate for about a day in the blood stream before developing into mature red blood cells. Like mature red blood cells,...
s can increase MCV. In pernicious anemia
Pernicious anemia
Pernicious anemia is one of many types of the larger family of megaloblastic anemias...
(macrocytic), MCV can range up to 150 femtolitre
Femtolitre
The femto litre is the metric unit of volume equal to 10−15 litre, or one quinine cillionth or one quadrillionth litre. It is abbreviated FL or fl. One femto litre is the same as 1 μm3.1....
s. An elevated MCV is also associated with alcoholism
Alcoholism
Alcoholism is a broad term for problems with alcohol, and is generally used to mean compulsive and uncontrolled consumption of alcoholic beverages, usually to the detriment of the drinker's health, personal relationships, and social standing...
(as are an elevated GGT
Gamma glutamyl transpeptidase
Gamma-glutamyltransferase or gamma-glutamyl transpeptidase is an enzyme that transfers gamma-glutamyl functional groups...
and a ratio of AST
Aspartate transaminase
Aspartate transaminase , also called aspartate aminotransferase or serum glutamic oxaloacetic transaminase , is a pyridoxal phosphate -dependent transaminase enzyme . AST catalyzes the reversible transfer of an α-amino group between aspartate and glutamate and, as such, is an important enzyme in...
:ALT
Alanine transaminase
Alanine transaminase or ALT is a transaminase enzyme . It is also called serum glutamic pyruvic transaminase or alanine aminotransferase ....
of 2:1). Vitamin B12
Vitamin B12
Vitamin B12, vitamin B12 or vitamin B-12, also called cobalamin, is a water-soluble vitamin with a key role in the normal functioning of the brain and nervous system, and for the formation of blood. It is one of the eight B vitamins...
and/or folic acid
Folic acid
Folic acid and folate , as well as pteroyl-L-glutamic acid, pteroyl-L-glutamate, and pteroylmonoglutamic acid are forms of the water-soluble vitamin B9...
deficiency has also been associated with macrocytic anemia (high MCV numbers).
Low
The most common causes of microcytic anemiaMicrocytic anemia
Microcytic anemia is a generic term for any type of anemia characterized by small red blood cells. The normal mean corpuscular volume is 76-100 fL, with smaller cells as macrocytic....
are iron deficiency (due to inadequate diet
Diet (nutrition)
In nutrition, diet is the sum of food consumed by a person or other organism. Dietary habits are the habitual decisions an individual or culture makes when choosing what foods to eat. With the word diet, it is often implied the use of specific intake of nutrition for health or weight-management...
ary intake, gastrointestinal blood loss
Gastrointestinal bleeding
Gastrointestinal bleeding or gastrointestinal hemorrhage describes every form of hemorrhage in the gastrointestinal tract, from the pharynx to the rectum. It has diverse causes, and a medical history, as well as physical examination, generally distinguishes between the main forms...
, or menstrual blood loss
Menstruation
Menstruation is the shedding of the uterine lining . It occurs on a regular basis in sexually reproductive-age females of certain mammal species. This article focuses on human menstruation.-Overview:...
), thalassemia
Thalassemia
Thalassemia is an inherited autosomal recessive blood disease that originated in the Mediterranean region. In thalassemia the genetic defect, which could be either mutation or deletion, results in reduced rate of synthesis or no synthesis of one of the globin chains that make up hemoglobin...
, or chronic disease. In iron deficiency anemia
Iron deficiency anemia
Iron-deficiency anemia is a common anemia that occurs when iron loss occurs, and/or the dietary intake or absorption of iron is insufficient...
(microcytic anemia), it can be as low as 60 to 70 femtolitres. In some cases of thalassemia
Thalassemia
Thalassemia is an inherited autosomal recessive blood disease that originated in the Mediterranean region. In thalassemia the genetic defect, which could be either mutation or deletion, results in reduced rate of synthesis or no synthesis of one of the globin chains that make up hemoglobin...
, the MCV may be low even though the patient is not iron deficient.
A low MCV number in a patient with a positive stool guaiac test
Stool guaiac test
The stool guaiac test or guaiac fecal occult blood test is one of several methods that detect the presence of fecal occult blood...
(bloody stool) is highly suggestive of GI cancer.
See also
- Anemia: Differential Diagnosis
- Full blood count
- Mean corpuscular hemoglobinMean corpuscular hemoglobinThe mean corpuscular hemoglobin, or "mean cell hemoglobin" , is the average mass of hemoglobin per red blood cell in a sample of blood. It is reported as part of a standard complete blood count...