Saturday, August 1, 2009

Labs: Complete Blood Count (CBC)

I'll be starting on a segment that covers the topics of laboratory tests and procedures to try and explain what these things are and what their results mean. Here's one of the most basic but also most important blood tests.

The Complete Blood Count (CBC) is one of the most basic lab tests used to monitor a person's health. The ability of the CBC to check for a large array of potential problems like infections, anemia, bleeding, and even certain types of cancers makes it one of the most important blood tests.

Results of a complete blood count would look like the following:

click on image to enlarge

Notice that there are three columns present. On the left most column, you will see the different components that make up a CBC. The middle column represents the results of the blood tests in their proper units. And on the right most column are the reference levels for each blood component. Reference levels tell us between what levels the results should fall under to be considered normal. It is then the job of the physician to figure out what is happening should anything fall outside the reference levels. It is worthwhile to mention that different laboratories often have different sets of reference values, depending on which standard unit of measurement they use.

Knowing what each column stands for, we now delve into understanding the important components.

The complete blood count test is divided into four distinct categories.

Part I: White Blood Cell Count and its components

The first five entries in the example represent the WBC Count and the different components that make up the white blood cells that are present. The neutrophils, lymphocytes, monocytes and eosinophils represent different types of white blood cells each having a different function in the protecting the body from infection. The figure that we are interested in is the WBC count which gives us a general picture of the body's defenses.

Part II: Red Blood Cells and its components

The amount of blood we have circulating in our bodies is important. it is what allows our organs to function properly. The red blood cell count is the amount of blood present, with the hemoglobin indicating how much of those red blood cells are carrying oxygen, while hermatocrit tells us how much of our blood is made up of red blood cells.

The three components often move in tandem to each other.

Part III: Platelet count

Platelets are a special type of blood cells that help our bodies close wounds.

Part IV: Red Blood Cell ratios

The MCV, MCH, MCHC, MPV and RDW are ratios that provide us with information about the red blood cells. They come into play when anemia is present, as the sizes and shapes of the red blood cells sometimes can pinpoint the cause.

Now that we know what each component is, we need to understand means and what do levels outside the reference range indicate. Below is a chart explaining this.

click on image to enlarge

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