Diagnostic sign

A medical sign is an objective indication of some medical fact or characteristic that may be detected by a patient or anyone, especially a physician, before or during a physical examination of a patient. For example, whereas a tingling paresthesia is a symptom (only the person experiencing it can directly observe their own tingling feeling), erythema is a sign (anyone can confirm that the skin is redder than usual). 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 ends of fingers (which may be a sign of lung disease, or many other things), a staggering gait (human) and arcus senilis of the eyes.

The term sign is not to be confused with the term indication, which in medicine denotes a valid reason for using some treatment.

The art of interpreting clinical signs was originally called semiotics (a term now used for the study of sign communication in general) in English. This term, then written semeiotics (derived from the Greek adjective σημειωτικός: semeiotikos, "to do with signs"), was first used in English in 1670 by Henry Stubbes (1631–1676), to denote the branch of medical science relating to the interpretation of signs:

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