Signs and symptoms are the observed or detectable signs, and experienced symptoms of an illness, injury, or condition. A sign for example may be a higher or lower temperature than normal, raised or lowered blood pressure or an abnormality showing on a medical scan. A symptom is something out of the ordinary that is experienced by an individual such as feeling feverish, a headache or other pain or pains in the body.
A medical sign is an objective indication of a disease, injury, or abnormal physiological state that may be detected during a physical examination. These signs are visible or otherwise detectable such as a rash or bruise. Medical signs assist in arriving at an accurate diagnosis.
A symptom is something felt or experienced, such as pain or dizziness. Signs and symptoms are not mutually exclusive, for example a subjective feeling of feverishness can be noted as sign by using a thermometer that registers a high reading.
Signs and symptoms are often nonspecific, but some combinations can be suggestive of certain diagnoses helping to narrow down what may be wrong. In other cases when known as cardinal signs and symptoms they are specific even to the point of being pathognomonic. A cardinal sign or cardinal symptom can also refer to the major sign or symptom of a disease.
Examples of signs include elevated blood pressure, nail clubbing of the fingernails or toenails, staggering gait, and arcus senilis and arcus juvenilis of the eyes. A sign is distinguished from an indication which is a specific reason for using a particular treatment.
Signs are different from experienced symptoms. A sign of a disorder is something that may be observed by another or detected during a medical examination or procedure.:75 For example high blood pressure may be noted as a sign during an examination for which there have been no reported symptoms. A symptom is something experienced and reportable by a person such as a headache or fatigue.
There is some overlap between signs and symptoms--certain things may qualify as both a sign and a symptom, such as a bloody nose.
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".:73–74 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.":77
"[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.":81
Symptoms may be mild or severe, brief or longer-lasting when they may become reduced or then recur. Constitutional symptoms are those related to the systemic effects of a disease such as fever, malaise, and weight loss. They affect the entire body rather than a specific part.
The terms "chief complaint", "presenting symptom", "iatrotropic symptom", or "presenting complaint" are used to describe the initial concern when an individual seeks medical help. The symptom that ultimately leads to a diagnosis is called a cardinal symptom.
Non-specific signs and symptoms are self-reported symptoms that do not indicate a specific disease process or involve an isolated body system. For example, fatigue is a feature of many acute and chronic medical conditions, and may be either a primary or secondary symptom. Fatigue is also a normal, healthy condition when experienced after exertion or at the end of a day.
Sensory symptoms can also be described as positive or negative depending on whether the symptom is abnormally present such as tingling or itchiness, or abnormally absent such as loss of smell. The following terms are used for negative symptoms - hypoesthesia is a partial loss of sensitivity to moderate stimuli, such as pressure, touch, warmth, cold. Anesthesia is the complete loss of sensitivity to stronger stimuli, such as pinprick. Hypoalgesia (analgesia) is loss of sensation to painful stimuli. Symptoms are also grouped in to negative and positive for some mental disorders such as schizophrenia. Positive symptoms are those that are present in the disorder and are not normally experienced by most individuals and reflects an excess or distortion of normal functions. Examples are hallucinations, delusions, and bizarre behavior. Negative symptoms are functions that are normally found but that are diminished or absent such as apathy and anhedonia.
Medical signs may be classified by the type of inference that may be made from their presence, for example:
Some signs and symptoms occur in a wide range of disease processes, whereas other symptoms are fairly specific for a narrow range. For example, a sudden loss of sight in one eye has a significantly smaller number of possible causes than nausea does. Some symptoms can be misleading as a result of referred pain, where for example a pain in the right shoulder may be due to an inflamed gallbladder and not to presumed muscle strain.
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 co-operative interaction between the physician and patient; 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".:82
The introduction of the techniques of percussion and auscultation into medical practice altered the relationship between physician and patient in a significant way, specifically because these techniques relied almost entirely upon the physician listening to the sounds of the patient's body.
Not only did this development 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 changes took place in medical practice, it was increasingly necessary to uniquely identify data that were 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.:89
In some senses, the process of diagnosis is a matter of assessing the likelihood that a given condition is present. Haemoptysis (coughing up blood) for example is much more likely to be caused by a respiratory disease than by a broken toe. Each question asked in taking the medical history can narrow down the 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 (blood tests, radiology, scans, a biopsy, etc.) 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 (a swollen, tender, distorted lower leg) 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--and, for example, if the x-ray were to show a fractured tibia, the film would be diagnostic of the fracture.
A symptom (from Greek , "accident, misfortune, that which befalls", from , "I befall", from - "together, with" and , "I fall") is a departure from normal function or feeling. Symptomatology (also called semiology) is a branch of medicine dealing with the signs and symptoms of a disease. This study also includes the indications of a disease. It was first described as semiotics by Henry Stubbe in 1670 a term now used for the study of sign communication.