Blood Count Test Terminology

Blood Count Test Terminology
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  • 0:02 Blood Testing
  • 1:37 Blood Counts
  • 5:14 Lesson Summary
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Lesson Transcript
Instructor: Adrianne Baron

Adrianne has taught high school and college biology and has a master's degree in cancer biology.

We are going to discuss how healthcare professionals get counts of the various types of cells in blood. We will cover normal ranges and the names used when the counts are not normal.

Blood Testing

There are many different healthcare professions that you may decide to enter. One area that you are interested in is the field of phlebotomy, which deals with drawing blood from a patient. If you become a healthcare professional that draws blood, then your title will be phlebotomist.

You want to be very well informed before making your final decision on becoming a phlebotomist. You strike up a conversation with the phlebotomist, Kia, that works at your doctor's office during an office visit. Kia lets you know some of the basic information about being a phlebotomist.

One of the things that Kia covers is how to read blood draw orders from the doctor. You learn that stat means immediately. The doctor will add this to a blood draw order if the results are needed right away for a patient.

Kia says that you also have to know how the blood is to be drawn from the patient. This changes depending on the type of test being performed. The first and simplest way of getting blood is through doing a capillary puncture or withdrawing blood from the capillaries under the skin using a lancet. A lancet is a short needle that punctures just below the skin. Capillary punctures are only done when only a small amount of blood is needed for blood tests.

Phlebotomists perform a venipuncture, the surgical withdrawal of blood from the veins, if a larger amount of blood is needed. This procedure uses a syringe, a cylinder with a plunger in it used to withdraw and/or inject fluid, or a needle, vacuum system and blood collection tubes.

Blood Counts

Next, Kia tells you about blood count tests, starting with the simplest test first, the hematocrit, or Hct for short. She explains that this is a test to determine the percentage of blood that is occupied by red blood cells. This test is done by capillary puncture. Normal range for a hematocrit varies by sex and age. The normal range for adult females is 59-45% and the range for adult males is 39-50%. A low red blood cell percentage can indicate anemia, and a high percentage of red blood cells can indicate polycythemia.

Kia says they can also determine the number of red blood cells in a set amount of blood in a test known as the red blood cell count. The ideal number of red blood cells is between 4-5 million for females and 4.5-6 million in males per cubic mm of blood. A cubic mm of blood is equivalent to a single drop.

You ask if there are tests for the other blood cells. Kia confirms that there are tests for each type of blood cell. She breaks them down for you.

Blood draws can also be used to take a platelet count in order to determine the number of platelets or thromobocytes in a cubic mm of blood. The expected amount of platelets is anywhere from 140,000-340,000 per cubic mm. Anytime a patient has a low platelet count, we refer to this as thrombocytopenia. A higher-than-normal platelet count is referred to as thromobocytosis. You figure you can remember these terms easily since you already know that 'thromb/o' means 'thromobocytes' and the suffix '-penia' means 'decreased or few.'

Kia then begins to explain about the white blood cell count, or count of all white blood cells (or WBCs) in a cubic mm of blood. The normal white blood cell count range is 5,000-9,000 WBCs for everyone regardless of age or sex. 'Leuk/o' means 'white blood cells,' and the term for low WBC count is leukopenia, and the term for high WBC count is leukocytosis.

There is another test that may go along with the WBC count. The white blood cell differential test is a test to determine the percentage of each of the five different types of WBCs. Kia explains that the body needs more of certain WBCs and less of others so they measure the percentages. Ideally, we want neutrophils to make up 60-70%, lymphocytes 20-25%, monocytes 3-8%, eosinophils 2-4% and basophils .5-1%.

The most comprehensive test that you two discuss is the complete blood count, which is typically abbreviated as CBC. You already know enough to know that a CBC is a count of all of the different blood cells in a particular volume of blood. This is the most common test that is run since it gives a count for each type of blood cell.

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