The Blood Test for Syphilis
It seems desirable at this point, while we are trying to fix in mind the
great value of recognizing syphilis in a person in order to treat it and
thus prevent dangerous complications, to say something about the blood
test for syphilis, the second great advance in our means of recognizing
doubtful or hidden forms of the disease. The first, it will be recalled,
is the identification of the germ in the secretions from the early
sores.
+Antibodies in the Blood in Disease.+--It is part of the new
understanding we have of many diseases that we are able to recognize
them by finding in the blood of the sick person substances which the
body makes to neutralize or destroy the poisons made by the invading
germs, even when we cannot find the germs themselves. These substances
are called antibodies, and the search for antibodies in different
diseases has been an enthusiastic one. If we can by any scheme teach the
body to make antibodies for a germ, we can teach it to cure for itself
the disease caused by that germ. So, for example, by injecting dead
germs as a vaccine in typhoid fever and certain other diseases, we are
able to teach the body to form protective substances which will kill any
of the living germs of that particular kind which gain entrance to the
body. Conversely, if the body is invaded by a particular kind of germ,
and we are in doubt as to just which one it is, we can identify it by
finding in the blood of the sick person the antibody which we know by
certain tests will kill or injure a certain germ. This sort of medical
detective work was first applied to syphilis successfully by Wassermann,
Neisser, and Bruck in 1904, and for that reason the test for these
antibodies in the blood in syphilis is called the Wassermann reaction.
To be sure, it is now known that in syphilis it is not a true antibody
for the poisons of the Spirochæta pallida for which we are testing, but
rather a physical-chemical change in the serum of patients with
syphilis, which can be produced by other things besides this one
disease. But this fact has not impaired the practical value of the test,
since the other conditions which give it are not likely to be confused
with syphilis in this part of the world. The fact that no true antibody
is formed simply makes it unlikely that we shall ever have a vaccine for
syphilis.
+Difficulties of the Test.+--The Wassermann blood test for syphilis is
one of the most complex tests in medicine. The theory of it is beyond
the average man's comprehension. A large number of factors enter into
the production of a correct result, and the attaining of that result
involves a high degree of technical skill and a large experience. It is
no affair for the amateur. The test should be made by a specialist of
recognized standing, and this term does not include many of the
commercial laboratories which spring up like mushrooms in these days of
laboratory methods.
+The Recognition of Syphilis by the Blood Test.+--When the Wassermann
test shows the presence of syphilis, we speak of it as "positive."
Granted that the test is properly done, a strong positive reaction means
syphilis, unless it is covered by the limited list of exceptions. After
the first few weeks of the disease, and through the early secondary
period, the blood test is positive in practically all cases. Its
reliability is, therefore, greatest at this time. Before the infection
has spread beyond the first sore, however, the Wassermann test is
negative, and this fact makes it of little value in recognizing early
primary lesions. In about 20 to 30 per cent of syphilitic individuals
the test returns to negative after the active secondary stage is passed.
This does not necessarily mean that the person is recovering. It is even
possible to have the roof fall out of the mouth from gummatous changes
and the Wassermann test yet be negative. It is equally possible, though
unusual, for a negative Wassermann test to be coincident with contagious
sores in the mouth or on the genitals. So it is apparent that as an
infallible test for syphilis it is not an unqualified success. But
infallibility is a rare thing in medicine, and must be replaced in most
cases by skilful interpretation of a test based on a knowledge of the
sources of error. We understand pretty clearly now that the Wassermann
test is only one of the signs of syphilis and that it has quite
well-understood limitations. It has revealed an immense amount of
hidden syphilis, and in its proper field has had a value past all
counting. Experience has shown, however, that it should be checked up by
a medical examination to give it its greatest value. Just as all
syphilis does not show a positive blood test, so a single negative test
is not sufficient to establish the absence of syphilis without a medical
examination. In a syphilitic, least of all, is a single negative
Wassermann test proof that his syphilis has left him. In spite of these
rather important exceptions, the Wassermann test, skilfully done and
well interpreted, is one of the most valuable of modern medical
discoveries.
+The Blood Test in the Treatment and Cure of Syphilis.+--In addition to
its value in recognizing the disease, the Wassermann test has a second
field of usefulness in determining when a person is cured of syphilis,
and is an excellent guide to the effect of treatment. Good treatment
early in a case of syphilis usually makes the Wassermann test negative
in a comparatively short time, and even a little treatment will do it in
some cases. But will it stay negative if treatment is then stopped? In
the high percentage of cases it will not. It will become positive again
after a variable interval, showing that the disease has been suppressed
but not destroyed. For that reason, if we wish to be sure of cure, we
must continue treatment until the blood test has become negative and
stays negative. This usually means repeated tests, over a period of
several years, in connection with such a course of treatment as will be
described later. During a large part of this time the blood test will
be the only means of finding out how the disease is being affected by
the treatment. To all outward appearance the patient will be well. He
may even have been negative in repeated tests, and yet we know by
experience that if treatment is stopped too soon, he will become
positive again. There is no set rule for the number of negative tests
necessary to indicate a cure. The whole thing is a matter of judgment on
the part of an experienced physician, and to that judgment the patient
should commit himself unhesitatingly. If a patient could once have
displayed before him in visible form the immense amount of knowledge,
experience, and labor which has gone into the devising and goes into the
performing of this test, he would be more content to leave the decision
of such questions to his physician than he sometimes is, and would be
more alive to its reality and importance. The average man thinks it a
rather shadowy and indefinite affair on which to insist that he shall
keep on doctoring, especially after the test has been negative once or
twice.
Just as a negative test may occur while syphilis is still actively
present and doing damage in the body, so a positive Wassermann test may
persist long after all outward and even inward signs of the disease have
disappeared. These fixed positives are still a puzzle to physicians. But
many patients with fixed positives, if well treated regardless of their
blood test, do not seem to develop the late accidents of the disease. If
their nervous systems, on careful examination, are found not to be
affected, they are reasonably safe as far as our present knowledge
goes. People with fixed positives should accept the judgment of their
physicians and follow their recommendations for treatment without
worrying themselves gray over complications which may never develop.
+Practical Points About the Test.+--Certain practical details about this
test are of interest to every one. Blood for it is usually drawn from a
small vein in the arm. The discomfort is insignificant--no more than
that of a sharp pin-prick. Blood is drawn in the same way for other
kinds of blood tests, so that a needle-prick in the arm is not
necessarily for a Wassermann test. There is no cutting and no scar
remains. The amount of blood drawn is small and does not weaken one in
the least. The test is done on the serum or fluid part of the blood,
after the corpuscles are removed. It can also be done on the clear fluid
taken from around the spinal cord, and this is necessary in certain
syphilitic nervous diseases. There is nothing about the test that need
make anybody hesitate in taking it, and it is safe to say that, when
properly done, the information that it gives is more than worth the
trouble, especially to those who have at any time been exposed, even
remotely, to the risk of infection. But the test must be well done, by a
large hospital or through a competent physician or specialist, and the
results interpreted to the patient by the physician and not by the
laboratory that does the test, or in the light of the patient's own
half-knowledge of the matter.