A medical sign is an objective indication of some medical fact or
characteristic that may be detected by a physician during a physical examination
of a patient. For example, whereas paresthesia is a symptom, erythema is a
sign. Symptoms and signs are often nonspecific, but often combinations of
them are at least suggestive of certain diagnoses, helping to narrow down what
may be wrong. In other cases they are specific even to the point of being
pathognomonic. Some signs may have no meaning to the
patient, and may even go unnoticed, but may be meaningful and significant to the
healthcare provider in assisting diagnosis.
Examples of signs include elevated blood pressure, a clubbing of the fingers, and
arcus senilis. The term sign is not to be confused with
the term indication, which denotes a valid reason for using some treatment.
Signs and semiotics The art of interpreting clinical signs
was originally called semiotics in English. This term, then written
semeiotics, was first used in English in 1670 by Henry Stubbes, to denote the
branch of medical science relating to the interpretation of signs:
…nor is there any thing to be relied upon in Physick, but an exact knowledge
of medicinal phisiology, semeiotics, method of curing, and tried medicines….
Eponymous signs Historically, medical signs were named
after the physicians who first described them.
Signs versus symptoms Signs are different from symptoms, the
subjective experiences, such as fatigue, that patients might report to their
examining physician. For convenience, signs are commonly
distinguished from symptoms as follows: Both are something abnormal, relevant to
a potential medical condition, but a symptom is experienced and reported by
the patient, while a sign is discovered by the physician during examination or
by a clinical scientist by means of an in vivo examination of the patient.
A slightly different definition views signs as any indication of a medical
condition that can be objectively observed, whereas a symptom is merely
any manifestation of a condition that is apparent to the patient. From this
definition, it can be said that an asymptomatic patient is uninhibited by
disease. However, a doctor may discover the sign hypertension in an asymptomatic
patient, who does not experience "dis-ease", and the sign indicates a
disease state that poses a hazard to the patient. With this set of definitions,
there is some overlap – certain things may qualify as both a sign and a
symptom. Lester S. King, author of Medical
Thinking, argues that an "essential feature" of a sign is that there is both
a sign [or "signifier"] and a "thing signified". And, because "the essence of
a sign is to convey information", it can only be a sign, properly speaking, if it
has meaning. Therefore, "a sign ceases to be a sign when you cannot read it". A
person, who has and exercises the knowledge required to understand the
significance or indication or meaning of the sign, is necessary for something to
be a complete sign. A physical phenomenon that is not actually
interpreted as a sign pointing to something else is, in medicine, merely a
symptom. Thus, King rejects "these present-day views [distinguishing signs
from symptoms based on patient-subjective versus
clinician-objective], however widely accepted, as quite faulty, at variance
not only with ordinary usage but with the entire history of medicine."
Types of signs Medical signs may be classified by the
type of inference that may be made from their presence, for example:
Prognostic signs: signs that indicate the outcome of the current bodily state
of the patient. Prognostic signs always point to the future. Perhaps the most
famous prognostic sign is the facies Hippocratica:
"[If the patient's facial] appearance may be described thus: the nose sharp,
the eyes sunken, the temples fallen in, the ears cold and drawn in and their
lobes distorted, the skin of the face hard, stretched and dry, and the colour
of the face pale or dusky.… and if there is no improvement within [a prescribed
period of time], it must be realized that this sign portends death."
Anamnestic signs: signs that, indicate the past existence of a certain disease
or condition. Anamnestic signs always point to the past.
Diagnostic signs: signs that lead to the recognition and identification of a
disease. Pathognomonic signs: the particular
signs whose presence means, beyond any doubt, that a particular disease is
present. They represent a marked intensification of a diagnostic sign.
Singular pathognomonic signs are relatively uncommon.
"[Thus] a symptom is a phenomenon, caused by an illness and observable
directly in experience. We may speak of it as a manifestation of illness. When
the observer reflects on that phenomenon and uses it as a base for further
inferences, then that symptom is transformed into a sign. As a sign it
points beyond itself — perhaps to the present illness, or to the past or to
the future. That to which a sign points is part of its meaning, which may be
rich and complex, or scanty, or any gradation in between. In medicine, then,
a sign is thus a phenomenon from which we may get a message, a message that
tells us something about the patient or the disease. A phenomenon or observation
that does not convey a message is not a sign. The distinction between signs and
symptom rests on the meaning, and this is not perceived but inferred."
Technological development creating signs detectable only by physicians
Prior to the nineteenth century there was little difference in the powers of
observation between physician and patient. Most medical practice was
conducted as a joint co-operative interaction between the physician and
his aristocratic patient as equals; this was gradually replaced by a "monolithic
consensus of opinion imposed from within the community of medical investigators".
Whilst each noticed much the same things, the physician had a more
informed interpretation of those things: "the physicians knew what the findings
meant and the layman did not". = Advances in the 19th century=
However, the patient was gradually removed from the medical interaction due
to significant technological advances such as:
The 1808 introduction of the percussion technique:
"The process through which "the physician can assess the state of the
underlying lung by sensing the character of vibrations by gentle taps on the
chest wall [something which] greatly facilitated the diagnosis of pneumonia
and other respiratory diseases" The techniques, which had been first
described by the Viennese physician Leopold Auenbrugger in 1761, became far
more widely known following the publication of Jean-Nicolas Corvisart's
translation of Auenbrugger's work in 1808.
The 1819 introduction by René Laennec of the technique of auscultation. Laennec's
publication was translated into English, 1821–1834, by John Forbes.
The 1846 introduction by surgeon John Hutchinson of the spirometer, an
apparatus for assessing the mechanical properties of the lungs via measurements
of forced exhalation and forced inhalation. and obstructive diseases.)
The 1851 invention by Hermann von Helmholtz of the ophthalmoscope, which
allowed physicians to examine the inside of the human eye.
The immediate widespread clinical use of Sir Thomas Clifford Allbutt's six inch
pocket clinical thermometer, which he had devised in 1867.
The 1895 clinical use of X-rays which began almost immediately after they had
been discovered that year by Wilhelm Conrad Röntgen.
The 1896 introduction of the sphygmomanometer, designed by Scipione
Riva-Rocci, to measure blood pressure. = Alteration of the relationship between
physician and patient= The introduction of the techniques of
percussion and auscultation into medical practice altered the relationship
between physician and patient in a very significant way, specifically because
these techniques relied almost entirely upon the physician listening to the
sounds of the patients body. Not only did this development greatly
reduce the patient's capacity to observe and contribute to the process of
diagnosis, it also meant that the patient was often instructed to stop
talking, and remain silent. As these sorts of evolutionary changes
continued to take place in medical practice, it was increasingly necessary
to uniquely identify data that was accessible only to the physician, and to
be able to differentiate those observations from others that were also
available to the patient, and it just seemed natural to use "signs" for the
class of physician-specific data, and "symptoms" for the class of observations
available to the patient. King proposes a more advanced notion;
namely, that a sign is something that has meaning, regardless of whether it is
observed by the physician or reported by the patient:
The belief that a symptom is a subjective report of the patient, while
a sign is something that the physician elicits, is a 20th-century product that
contravenes the usage of two thousand years of medicine. In practice, now as
always, the physician makes his judgments from the information that he
gathers. The modern usage of signs and symptoms emphasizes merely the source of
the information, which is not really too important. Far more important is the use
that the information serves. If the data, however derived, lead to some
inferences and go beyond themselves, those data are signs. If, however, the
data remain as mere observations without interpretation, they are symptoms,
regardless of their source. Symptoms become signs when they lead to an
interpretation. The distinction between information and inference underlies all
medical thinking and should be preserved.
Signs as tests In some senses, the process of diagnosis
is always a matter of assessing the likelihood that a given condition is
present in the patient. In a patient who presents with haemoptysis, the
haemoptysis is very much more likely to be caused by respiratory disease than by
the patient having broken their toe. Each question in the history taking
allows the medical practitioner to narrow down their view of the cause of
the symptom, testing and building up their hypotheses as they go along.
Examination, which is essentially looking for clinical signs, allows the
medical practitioner to see if there is evidence in the patient's body to
support their hypotheses about the disease that might be present.
A patient who has given a good story to support a diagnosis of tuberculosis
might be found, on examination, to show signs that lead the practitioner away
from that diagnosis and more towards sarcoidosis, for example. Examination
for signs tests the practitioner's hypotheses, and each time a sign is
found that supports a given diagnosis, that diagnosis becomes more likely.
Special tests also allow a hypothesis to be tested. These special tests are also
said to show signs in a clinical sense. Again, a test can be considered
pathognonomic for a given disease, but in that case the test is generally said
to be "diagnostic" of that disease rather than pathognonomic. An example
would be a history of a fall from a height, followed by a lot of pain in the
leg. The signs are only very strongly suggestive of a fracture; it might not
actually be broken, and even if it is, the particular kind of fracture and its
degree of dislocation need to be known, so the practitioner orders an x-ray. The
x-ray film shows a fractured tibia, so the film is said to be diagnostic of the
fracture. Examples of signs
See also References
External links Who Named It?[2]: eponymous signs.