CLINICAL LAB SCIENEC

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ESSENTIALS OF CLINICAL LABORATORY SCIENCE
certain antigen, then it is presumed that the patient is infected or has been exposed
and maintains a certain level of antibodies. This system is explained thoroughly in
anatomy and physiology classes as well as academic classes for immunology and
serology.
Some direct tests are available in a few cases. Antigens present in blood or body
fluids and human wastes may be tested for directly, such as parasites in the blood
(e.g., malaria) or in the stool of a patient. Some tests in serology and immunology
use a system in which radioactive, enzymatic, and other “tags” are attached
to an antigen or antibody. These tagged antigens or antibodies are then counted
or otherwise detailed for the degree of infection. Other technologically advanced
procedures are either available or on the drawing board. This component of the
laboratory will most likely offer the most advances for new procedures in the
future.
The student will be exposed to only a few basic procedures to begin developing
the awareness and skills required to perform most serological tests. Some are
rather simple slide tests and others offer results that are semiquantitative, such
as dilutions of serum. Many simple slide tests are now available for at-home testing,
such as the home pregnancy test, which is actually an antigen-antibody reaction.
The tests offered here are only a few of the most basic procedures to help
orient the new student to the clinical laboratory, and not to train the student to
be technologically competent. That will come later in a comprehensive program
for medical laboratory technology.
In the Lab
BASIC SEROLOGY PROCEDURES
MANUAL SEROLOGY PROCEDURE #1
Serial Dilution Procedure (Two-Fold Antibody Titer)
Principles
Serial dilutions are used for a number of purposes in a clinical laboratory. Dilutions of
serum or plasma are often required for a variety of semi-quantitative and quantitative
serological tests. The serial dilution titer is often ordered for certain infectious
diseases where dilutions of serum are required for the performance of quantitative tests.
The physician may use this procedure to determine if a patient is successfully
combating an infection, is in an acute or convalescent state, or has an immunodeficiency.
Most often, the dilution will be made of antibodies found in the serum or
plasma. In some cases, the dilutions will be made of antigens.
Perhaps the most common serial dilution is the antibody titer. The antibody titer
procedure is based on the humoral response of a patient to his or her infective state.
In these cases, serial dilutions of the patient’s serum to determine a semi-quantitative
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