When your blood is drawn and sent to a laboratory for testing, a specially trained lab tech will test your blood. Lab techs typically have either a Bachelor's college degree in Medical Technology, or an Associate's degree. To be certified, they must take and pass a national examination. A phlebotomist (blood drawer) or a lab aide will typically draw your blood. Sometimes a nurse will draw your blood and send it to the lab for testing.
The most common blood test that doctors order is called the CBC-the Complete Blood Count. Some labs refer to it as an ABC-Automated Blood Count. The lab counts the cells in your blood-the red cells (RBC's), white cells (WBC's), and platelets. This is done in the Hematology department of the lab with sophisticated machines that the lab techs run, maintain, and troubleshoot.
Normal values given here are average ranges. Different laboratories use different methods, yielding slightly different results.
The CBC (ABC) consists of the following tests:
- Red Blood Cell count (RBC count). Normal value for males is 4.2-5.6 million/mcl of blood. Normal value for females is 3.9-5.2 million/mcl of blood.
- Hemoglobin (hgb). This is a protein in rbc's that binds oxygen to carry the oxygen throughout the body. Normal value for males is 14-18 grams/dl of blood. Normal value for females is 12-16 grams/dl of blood.
- Hematocrit (hct). This is the percentage of red cells in your blood. About half of your blood is a liquid called plasma made up mostly of water, and the other half is cells. Most of these cells are red cells, which give your blood its red color. If your hct is low, you are anemic. Normal value for males is 40-54%. Normal for females is 37-47%. If your hct is about 40%, that means about 60% of your circulating blood is plasma.
- White Blood Cell count (WBC count). Normal value is 5,000-10,000 white blood cells/mcl of blood.
- Differential-a lab tech differentiates the five types of WBC's. The percentage of certain types of WBC's is higher in bacterial infections, other types are higher with allergies or parasitic infections, and another type is higher with viral infections. Today, this is usually done by a machine, but if the machine finds anything abnormal, a lab tech will recheck it under a microscope before reporting out a final result.
- Platelet count-counts the number of platelets in your bloodstream, which help function in the clotting process. Platelets are very tiny-the smallest of the blood cells. Normal range is 130,000-400,000/mcl of blood.
These are the basic tests of the CBC (ABC). Other values have to do with various parameters of the red blood cell. This test is done in the Hematology department of the laboratory.
After working 20 years as an ASCP certified Med Tech, I switched careers to teach science in an inner-city high school. I've written an inspirational memoir about the joys of teaching and the obstacles I fought. No Child Left Behind? The True Story of a Teacher's Quest by Elizabeth Blake on http://www.BarnesandNoble.com and Amazon. Drugs, gangs, a riot, shootings, murdered students, abusive principals - all contributed to the stress which eventually drove me from the students I loved. The book celebrates triumph over adversity. To read the first page, visit http://www.elizabethblakeonline.com