MCV - Kresser Institute Membership Site

Marker Name: MCV

REFERENCE RANGES FOR MCV:

Laboratory reference range: 79–97 fL

Functional reference range: 85–92 fL

DESCRIPTION:

Mean corpuscular volume (MCV) is one of the standard indices used to describe red blood cells. As the name implies, MCV provides an average volume of red blood cells. MCV is important for the differential diagnosis of anemia,¹ which is often defined as an abnormally low hematocrit or hemoglobin level.² An abnormally high MCV is called macrocytosis, while an abnormally low MCV is microcytosis. As such, diagnoses of anemia can be qualified as microcytic anemia, normocytic anemia, or macrocytic anemia, depending on MCV.³

MCV is reported as a single number, and it represents the mean volume across all red blood cells. For various diagnostic purposes, it is important to know whether the red blood cells are similar in volume or represent a wide range of volumes. For example, a normal MCV could reflect a collection of red blood cells that share a similar volume within the normal range or, just as easily, equal numbers of red blood cells that have abnormally low volumes and abnormally high volumes.

To determine the distribution of volumes in a sample, the MCV is evaluated with another measurement called the red blood cell distribution width, or RDW. The RDW can be either normal or elevated, as no biological state routinely results in an RDW that is lower than normal.⁴ A normal RDW generally means that the red blood cells in a sample have a similar volume, while a high RDW indicates red blood cells with varying volumes.

The volume of a red blood cell is determined by the amount of hemoglobin, ions, and water contained within it. As with other cells in the body, protein pumps regulate cationic and anionic content in red blood cells. Under normal conditions, red blood cells contain low sodium, high potassium, and very low calcium levels. If these protein pumps are dysfunctional, it can change the ion content within the cells and subsequently, the volume of red blood cells.⁵ Free water can move passively into and out of red blood cells through osmosis to areas of relatively high solute concentration. Alternatively, red blood cells contain specific water channels called aquaporins that can actively move water across the cell membrane.⁶

In certain cases, macrocytosis, or an elevated MCV, may occur without the presence of anemia. For example, pregnant women, newborns, and infants may have macrocytosis without anemia.⁷ Macrocytic anemia usually falls into one of four major categories: a nutritional deficiency, the adverse effect of a drug, a primary bone marrow disorder (e.g., leukemia, myelodysplastic disorder), or a chronic illness other than cancer. A wide array of medications and drug classes can cause macrocytosis, including antivirals, chemotherapeutic agents, anticonvulsants, and antimicrobials.^7,8

The most common cause of microcytic anemia is iron-deficiency anemia.⁹ Iron-deficiency anemia, in turn, is due to decreased iron intake, decreased absorption, chronic disease, or bleeding. The other major causes of microcytic anemia are thalassemia, sideroblastic anemia (either hereditary or acquired), and anemia of chronic disease.¹⁰ Certain drugs, nutritional deficiencies, and metal poisoning may also cause microcytic anemia.

Mean corpuscular volume is always measured in conjunction with other red blood cell indices such as mean corpuscular hemoglobin (MCH), mean corpuscular hemoglobin concentration (MCHC), and red cell distribution width (RDW).¹¹ Likewise, red blood cell indices are virtually always measured with a total red blood cell count, hemoglobin, and hematocrit, along with a reticulocyte count in some cases.

PATHOLOGICAL/CONVENTIONAL RANGE INDICATIONS: High in:^7,8,12

Aging
Pregnancy
Infancy
Nutrient imbalances
- Vitamin B12 deficiency
- Folate deficiency
Aplastic anemia
Hemolytic anemia
Reticulocytosis
Megaloblastic anemia
Liver disease
Excessive alcohol intake
Hypothyroidism
Leukemia
Multiple myeloma
Myelodysplastic syndrome (MDS) variants
Drugs
- Oral contraceptives
- Proton pump inhibitors
- Histamine H₂ receptor blockers
- Nitrous oxide
- Metformin
- Colchicine
- Triamterene
- Sulfasalazine
- Antimicrobials (e.g., pyrimethamine, sulfamethoxazole, trimethoprim, valacyclovir)
- Antiviral treatment of HIV infection (e.g., zidovudine, stavudine)
- Chemotherapeutic agents (e.g., hydroxyurea, cyclophosphamide, busulfan, methotrexate, azathioprine, mercaptopurine, cladribine, etc.)
- Anticonvulsants (e.g., phenytoin, valproic acid, primidone)

Low in:^9,10,13,14

Alpha and beta thalassemia
Sideroblastic anemia
Nutrient imbalances
- Iron deficiency
- Vitamin B6 deficiency
- Copper deficiency
- Lead poisoning
- Zinc poisoning
Chronic inflammation (e.g., chronic infection, malignancy, rheumatologic disorders, inflammatory bowel disease, chronic immune activation, and other inflammatory disorders)
Hemoglobinopathies
Inherited microcytic anemia
Hypothermia
Drugs
- Chloramphenicol
- Isoniazid
- Busulfan
- Penicillamine
- Linezolid

FUNCTIONAL RANGE INDICATIONS:

High in:

Same as conventional indications

Low in:

Same as conventional indications

References: