Mean Corpuscular Volume (MCV) Lab Values

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Outline

Objective:

Determine the significance and clinical use of  Mean Corpuscular Volume lab value in clinical practice

 

Lab Test Name:

Mean Corpuscular Volume

 

Description:

Provides a measure of the RBC volume averaged over millions of cells

MCV:

  • Average size volume of individual RBCs 
  • Determination of etiology of anemia

 

Indications:

Determining etiology of anemia:

  • Iron-deficient anemia
  • Pernicious anemia- B12 deficiency
  • Folic acid deficient anemia
  • Aplastic anemia- deficiency of all blood cell types

Normal Therapeutic Values:

Normal – 80-100 fL

Collection:

  • CBC 
  • Lavender tube

 

What would cause increased levels?

Elevated MCV: >100 fL

  • Macrocytosis- larger than normal RBCs
    • Folate/Vitamin B12 deficiency
  • Megaloblastic anemia
  • Reticulocytosis

 

What would cause decreased levels?

Low MCV:<80 fL

  • Microcytosis- a defect in hemoglobin synthesis resulting in smaller than normal RBCs
  • Iron deficiency anemia
  • Thalassemia- genetic disorder in which there is less hemoglobin in the body
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Transcript

Hey everyone, Abby here with nursing.com. This lesson covers MCV or mean corpuscular  volume. We’ll talk about the normal values and situations in which this lab would be increased or decreased. Let’s get started.  

 

mean corpuscular volume abbreviated as MCV measures the red blood cell volume averaged over millions of cells. Remember, the mean is an average. Now, the average size and volume of individual red blood cells is measured with this lab, but it also defines the etiology of anemia. So, we can determine, is it an iron deficiency? Is it B12 or folate? It helps us to see. Now, how it’s calculated, the MCV measured in femtoliters, is equal to 10 times the hematocrit value, divided by the red blood cell count. 

 

Now, when do you think we would have this test run? What would indicate it? Well, you already talked about anemia, right? Yeah. Kind of spoiled the surprise. It helps us to determine what the cause of the anemia is or what type. So, as mentioned, it could be iron deficiency, it could be a B12 or folate deficiency. It also could be just full blown bone marrow suppression, no red blood cells or other blood products. As you can see here, it’s measured on a CBC. It’s collected in a lavender tube. Normal values are between 80 and a hundred femtoliters. When non values are increased, that means that they’re above a hundred femtoliters. That indicates that there’s macrocytosis going on, or the red blood cells are larger than normal and that is a folate or vitamin B12 deficiency. We know that the vitamin B12 deficiency is our pernicious anemia, right? It could also be that the red blood cells are huge <laugh> megaloblastic anemia. It could also be in the case of an elevation in reticulocytes or young red blood cells, and this is just a sign that there’s an unusually rapid, really rapid request from the bone marrow to produce red blood cells.

 

 It will be decreased or below 80  femtoliters in microcytosis, or smaller than normal red blood cells. This is going to be the case in iron deficient anemia and a rare blood disorder, Thalassemia. Now, look at these images. You can see this is macrocytic and this is microcytic. That’s when we see the difference in lab values, let’s take a look at our linchpins. 

 

The mean corpuscular volume MCV lab measures the average size of red blood cells. They should range in size between 80 and a hundred  femtoliters. If it’s bigger than that, the red blood cells are huge and that is going to indicate a B12 or folate deficiency. If they’re small or really tiny red blood cells, we have an iron deficiency, therefore not allowing for those red cells to be formed as easily. And remember, as is typical in nursing and in general, these are labs that are never going to be used on their own for diagnosis. Keep in mind that big picture, right? Our patient has a lot going on. 

 

Well done. Everyone now go out and be your best self today and happy nursing.

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