$Unique_ID{BRK01668}
$Pretitle{Special Procedures and Laboratory Tests, Skin and Subcutaneous
Tissue}
$Title{Use of Different Methods for Tuberculosis Testing}
$Subject{test skin tuberculosis}
$Volume{P-20, L-20}
$Log{}

Copyright (c) 1991   Tribune Media Services, Inc.


Use of Different Methods for Tuberculosis Testing


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QUESTION:  Several members of our family were tested recently for the
possibility of tuberculosis.  When we discussed this later, we found that
different methods were being used and we wondered why.  One type of test did
not use a hypodermic needle, while the other did.  Are both these tests
recognized for testing for tuberculosis?  Please clear up our confusion, if
you can.

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ANSWER:  With the number of cases of tuberculosis on the upswing again, many
more Americans will be undertaking similar procedures, so I suppose it is a
fine idea to describe these tests to you in detail.  The test that did not use
a hypodermic syringe and needle is called the Tine Test.  It is a button with
several sharp points or "tines" that have been coated with either old
tuberculin (OT) or purified protein derivative (PPD) both of which cable of
causing a skin reaction in people who have antibodies to the tuberculosis
bacteria.  Since these antibodies are present only in people who have been
exposed to the bacteria, the skin reaction is an important finding.  The Tine
test is the not as sensitive as the other test, for the amount of tuberculin
that enters the skin can not be carefully controlled, and so the test is only
used as a screening test.  Since it is easy to perform, and quickly
accomplished it is just fine for this purpose, particularly in school
populations among young people.  However if the test is positive, the more
accurate test, with precise amounts of PPD must be used.  This test, which
uses a needle and syringe is called the Mantoux Test.  A precise amount of
PPD, 0.1 mL, is injected under the skin in the area of the arm, usually
between the wrist and the inner side of the elbow.  The arm is inspected from
3 to 5 days later, and if a reddened, hardened area has developed, it is
measured.  The size of this "induration" from 5 to over 15 mm, can be
significant, and may be interpreted as showing that the individual has been
exposed to infectious tuberculosis.  When the test is positive, other
examinations, including chest x-rays are indicated before treatment is
started.
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The material contained here is "FOR INFORMATION ONLY" and should not replace 
the counsel and advice of your personal physician.  Promptly consulting your 
doctor is the best path to a quick and successful resolution of any medical 
problem.
