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Name: Normandi
Status: Student
Grade:  9-12
Location: OH
Country: United States
Date: February 2006

How do you discover diseases in the bloodstream or in the blood cells?

One of the blood tests that is usually included in a general lab workup is called a CBC, which stands for complete blood count. This tests how many red blood cells, white blood cells, platelets you have, and the amount of hemoglobin you have in your red blood cells. If your white blood cell count is high or too low, a slide is made of the blood and looked at under the microscope. There are 5 kinds of white blood cells and the number of each is diagnostic because each has a job to do.

If there are a lot of neutrophils, this might mean that you have an active infection because their job is to kill bacteria. If you have too many lymphocytes and they look immature, you could have a viral infection or maybe mono. If the count is very very high and there are a lot of one type of white blood cell you might have leukemia. Malaria and other protozoal diseases can also be identified this way because you can see the organisms in the cells or between the cells.


In the case of many infectious diseases, the causative agent (bacteria and viruses) can usually be cultured from blood samples. In some cases, DNA from the bacterium or virus can be detected by the polmerase chain reaction. In some cases, the agent can be detected by immunoassay; antibodies specific for the bacterium or virus can be observed to bind to infected blood cells. In the case of some cancers (leukemia, for example), abnormal white blood cells can be observed microscopically. In the case of some cancers (colon and prostate), abnormal antigens (CA-125 and prostate specific antigen)can be detected in the blood using antibody tests.

Ron Baker, Ph.D.

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