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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Update: June 2012