Chelynn Hutchison English 2010

Complete blood count

It’s time for your annual exam visit, your doctor comes in does the physical exam and then orders all kinds of different blood test, maybe gives you a prescription and sends you on your way. As you leave you begin to wonder what the test are your doctor just ordered, why he ordered them and what they mean. All Doctors order various blood tests to determine what might be going on in your body. One of the most common blood test performed is the (CBC).

What is a CBC?

A Complete Blood Count, also known as Full Blood Count (FBC) or Full Blood Exam (FBE) or blood panel, is a test requested by a doctor or other medical professional that gives information about the cells in a patient’s blood. The cells that circulate in the bloodstream are generally divided into three types: white blood cells (leukocytes), red blood cells (erythrocytes), and (thrombocytes). Abnormally high or low counts may indicate the presence of many forms of disease, and hence blood counts are among the most commonly performed blood tests in medicine, as they can provide an overview of a patient’s general health status.

(Red blood cells picture found on www.medicinenet.com)

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What are the methods of testing blood?

There are three different ways of testing the blood once you have received it: Sample, Automated blood count and Manual blood count. We will briefly go over each one. First: Sample A phlebotomist collects the blood and then puts blood onto a slide, allowing time for it to dry. Then the slide is put under a microscope, read and counted. In the past this was the most common way CBC were performed, but because of modern technology this process is not used as often. Second: Automated blood count The blood is well mixed and placed on a rack in the analyzer. Blood counting machines aspirate a very small amount of the blood through narrow tubing. Within this tubing, there are sensors that count the number of cells going through it, and can identify the type of cell; this is flow cytometry. The two main sensors used are light detectors, and electrical impedance. One way the instrument can tell what type of blood cell is present is by size. In addition to counting, measuring and analyzing red blood cells, white blood cells and platelets, automated hematology analyzers also measure the amount of hemoglobin in the blood and within each . This information can be very helpful to a physician who, for example, is trying to identify the cause of a patient’s . If the red cells are smaller or larger than normal, or if there’s a lot of variation in the size of the red cells, this data can help guide the direction of further testing and expedite the diagnostic process so patients can get the treatment they need quickly.

(Complete blood count performed by an automated analyser. Picture found on www.medicinenet.com)

Third: Manual blood count Counting chambers that hold a specified volume of diluted blood (as there are far too many cells if it is not

2 diluted) are used to calculate the number of red and white cells per liter of blood. To identify the numbers of different white cells, a is made, and a large number of white cells are counted. This gives percentage of cells that are of each type. By multiplying the percentage with the total number of white blood cells, the absolute number of each type of white cell can be obtained. The advantage of manual counting is that automated analysers are not reliable at counting abnormal cells. That is, cells that are not present in normal patients and are only seen in the peripheral blood with certain hematological conditions.

What are the blood results?

Red cells  Total red blood cells- the number of red cells is given as an absolute number per liter.  Hemoglobin-the amount of hemoglobin in the blood, expressed in grams per deciliter. (Low hemoglobin is called anemia.)  or packed cell volume- this is the fraction of whole blood volume that consists of red blood cells. White blood cells  Total white blood cells- all the white cell types are given as a percentage and as an absolute number per liter. A complete blood count also includes:  Neutrophil granulocytes-may indicate bacterial infection. May also be raised in acute viral infections.  Lymphocytes- higher with some viral infections, also raised in leukemia.  Monocytes- may be raised in bacterial infection, tuberculosis, malaria, rocky mountain fever, leukemia, and chronic ulcerative colitis.  Eosiniophil granulocytes- increased in parasitic infections, asthma or allergic reaction  Basophil granulocytes-may be increased in bone marrow related conditions such as leukemia or lymphoma. What are the normal blood count levels?

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The following table explains what the normal ranges are for each of the components.

Parameter Reference Range Critical Value

WBC <1,000/uL >50,000/uL (if first 4,000 - 11,000/uL diagnosis) >100,000/uL (known patient)

RBC Males 4.31 - 5.84 mil/uL Females 4.00 - 5.00 mil/uL

Hemoglobin Males 13.0 - 17.0 g/dL <6.0 g/dL Females 12.0 - 15. 0 g/dL

Hematocrit <18% Males 40 - 50% >70% neonates up to 2 Females 36 - 45% mos >60% all others

MCV 80 - 99 fL

MCH 27 - 34 pg

MCHC 32 - 36%

Reticulocytes 0.4 - 1.8%

Immature Reticulocyte 0.0 - 0.16 Fraction

RDW <14.5%

Platelet Count <30,000/uL 140,000 - 400,000/uL >1 million/uL

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Mean 9.4 - 12.3 fL Volume

Immature Platelet 1.1 - 7.1% Fraction

Reference range for the WBC differential count is:

White Cell Relative Absolute

Bands 0 - 14% N/A

Neutrophils 45 - 78% 1.7 - 6.8 th/uL

Lymphocytes 15 - 47% 1.0 - 3.3 th/uL

Monocytes 0 - 12% 0.2 -0.9 th/uL

Eosinophils 0 - 7% 0.0 - 0.4 th/uL

Basophils 0 - 2% 0.0 - 0.2 th/uL

(Chart can be found at www.clinlabnavigator )

Is there anything else I should know?

While no specific pre-testing restrictions are necessary, it is best to avoid a fatty meal prior to having your blood drawn. So the next time you visit your doctor and they request a Complete Blood Count, you’ll be more knowledgeable.

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References

Complete Blood Count. (2010) Retrieved 2010, Feb. 1, from the MedicineNet web site:

www.medicinenet.com

Complete Blood Count. (2010) Retrieved 2010, Feb. 1, from the Lab Tests Online site:

www.labtestsonline.org

Lymphoma, Complete Blood Count. (2010) Retrieved 2010 Feb. 1, from the lymphoma site:

www.lymphomation.org

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