• Red Blood Cell Indices
• Red cell mass measurement
• Erythrocyte indices
• Mean Corpuscular Volume
• MCV

• Lavender top tube or EDTA microtainer
• 5 mL of whole blood or fill microtainer

This section details the Mean Corpuscular Volume (MCV) which is a routine part of the Complete Blood Count (CBC) test.

The MCV is the mean volume of a single RBC; which can be calculated from the RBC count and Hematocrit (Hct) using the following formula:

MCV (fl) = Hct (%) × 10/RBC (10¹²/L)

• The MCV is useful in the differential diagnosis of anemia
• Normocytosis = Normal MCV (normal RBC size 82-99 fL)
• Microcytosis = Decreased MCV (small RBC size <82 fL)
• Macrocytosis = Increased MCV (large RBC size >99 fL)

The MCV, is the mean volume of a single red blood cell and provides the basis for classifying anemias.

When the MCV is abnormal, but no anemia exists; an underlying condition is often present, but may not be severe enough to result in anemia.

A bimorphic population of RBCs (one that contains two sizes of RBCs) may result in a normal MCV; however, the RDW will be increased and the peripheral blood smear will be abnormal.

Please see the appropriate section for detailed information on what a normal, high or low MCV may be mean clinically.

The MCV test may be indicated for:

• Evaluation of Anemia
• Detection of a hematologic disorder, neoplasm or immunologic abnormality
• Determination of the presence of hereditary hematologic abnormalities
• Monitoring the effects of acute or chronic blood loss
• Monitoring hematologic status during pregnancy
• Monitoring patients with disorders associated with elevated or decreased erythrocyte counts
• Monitoring the progression of non-hematologic disorders associated with abnormal erythrocyte counts
• Adrenal dysfunction
• Bone marrow failure
• Cancers
• COPD
• Hypothyroidism
• Liver disease
• Malabsorption syndromes
• Renal disease
• Monitoring response to drugs or chemotherapy and to evaluate undesired reactions to drugs that may cause blood dyscrasias

Consult your laboratory for their normal ranges as these may vary somewhat from the ones listed below.

If there is anemia with normal MCV (82-99 fL); consider the following underlying conditions:

I. Anemia with appropriate bone marrow response

• Acute blood loss with anemia
• Hemolytic anemia (may be macrocytic when there is pronounced reticulocytosis)
• Prosthetic heart valves
• Sepsis

II. Anemia with impaired marrow response

• Drug suppression of bone marrow (e.g. chemotherapeutic agents)
• Marrow hypoplasia:
• Aplastic anemia
• Pure red cell aplasia
• Marrow infiltration:
• Infiltration by malignant cells
• Inherited storage diseases
• Myelofibrosis
• Decreased erythropoietin production (kidney disease)
• Endocrine deficiencies
• Liver disease
• Malnutrition

III. Anemia of chronic disease

• Carcinoma/Malignancy
• Crohn's disease
• Lymphoma
• Polymyalgia Rheumatica
• Renal disease
• Rheumatoid arthritis

Conditions with increased MCV (>99 fl):

I. Cobalamin (Vitamin B₁₂) deficiency

• Decreased ingestion:
• Lack of animal products
• Strict vegetarianism
• Impaired absorption:
• Anti-intrinsic factor antibody
• Celiac disease/Sprue
• Drug-induced malabsorption (e.g. Metformin)
• Gastrectomy (total or partial)
• Familial selective malabsorption (Imerslünd-Grasbeck syndrome)
• Gastric mucosal destruction (e.g. by caustics)
• Ileal resection
• Ileitis
• Infiltrative intestinal disease (e.g., lymphoma, scleroderma)
• Intrinsic factor deficiency or abnormality
• Intrinsic intestinal disease
• Pernicious anemia
• Zollinger-Ellison syndrome
• Competitive parasites:
• Fish tapeworm infestations (Diphyllobothrium latum)
• Increased requirements:
• Chronic pancreatic disease
• Hyperthyroidism
• Neoplastic disease
• Pregnancy
• Impaired utilization:
• Abnormal serum cobalamin binding protein
• Enzyme deficiencies
• IF deficiency
• Transcobalamin II deficiency
• r-binder deficiency
• Homocystinuria
• Methylmalonic aciduria
• Nitrous oxide administration

II. Folate Deficiency

• Decreased ingestion:
• Alcoholism
• Infancy
• Lack of vegetables
• Impaired absorption:
• Anticonvulsants
• Celiac disease/Sprue
• Intestinal short circuits
• Intrinsic intestinal disease
• Oral contraceptives
• Steatorrhea
• Increased requirements:
• Exfoliative skin disease
• Hypothyroidism
• Hyperactive hematopoiesis
• Infancy
• Neoplastic disease
• Pregnancy
• Impaired utilization:
• Folic acid antagonists (Methotrexate, triamterene, trimethoprim)
• Enzyme deficiencies
• Dihydrofolate reductase deficiency
• N⁵-methyl tetrahydrofolate — Homocysteine methyltransferase deficiency
• Increased losses:
• Hemodialysis

III. Other Causes

• Metabolic inhibitors:
• Deoxybonucleotide synthesis: Hydroxyurea, cytarabine, phenytoin, or severe iron deficiency
• Folate antagonists: Methotrexate, aminopterin, oral contraceptives
• Purine anaologs: 6-mercaptopurine, 6-thioguanine, azathioprine, acyclovir
• Pyrimidine synthesis: 6-azauridine, 5 fluorouracil, 5-azacitidine, zidovudine
• Inborn errors of metabolism:
• Deficiency of formiminotransferase
• Hereditary orotic aciduria
• Lesch-Nyhan syndrome
• Methyltransferase abnormality
• Other
• Alcoholism
• Cold agglutinins
• Drugs:
• AIDS (Zidovudine-Treated)
• Colchicines
• Pentamidine
• Pyrimethamine
• Triamterene
• Hyperglycemia
• Infection (HIV infection)
• Leukocytosis
• Reticulocytosis

Conditions with decreased MCV (<82 fl):

I. Disorders of iron metabolism

• Iron-deficiency anemia:
• Chronic blood loss (GI or menstrual losses, Carcinomas)
• Dietary inadequacy
• Increased iron loss
• Increased iron requirements
• Malabsorption
• Anemia of chronic disease
• Carcinoma
• Lymphoma
• Polymyalgia Rheumatica (usually normocytic)
• Renal disease
• Rheumatoid arthritis

• Congenital hypochromic-microcytic anemia with iron overload
• Shahidi-Nathan-Diamond syndrome
• Hereditary atransferrinemia

II. Disorders of porphyrin and heme synthesis

• Acute intermittent porphyria
• Acquired sideroblastic anemias
• Hereditary coproporphyria
• Hereditary sideroblastic anemia
• Idiopathic refractory sideroblastic anemia
• Drugs or toxins (ethanol, isoniazid, lead)
• Hereditary sideroblastic anemias
• X chromosome—linked, autosomal anemias
• Disorders of globin synthesis
• Thalassemias
• Hemoglobinopathies
• Sickle cell disease

III. Other

• Hereditary spherocytosis
• Metabolic
• Erythropoietin deficiency (usually normochromic microcytic)
• Hypothyroidism
• Hyperthyroidism
• Nitrofurantoin
• Post-splenectomy
• Pyridoxine responsive anemia (Vitamin B₆ deficiency anemia)
• RBC fragmentation (Marked)
• Whipple's disease

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