A medical sign is defined as objective evidence to an illness or disease. This sign is detectable by anyone, including both patient and physician, before or during a medical examination of the patient. For example, blood in the stool or vomit is a sign of an underlying illness or disease and can be recognised by both patient and doctor. On the other hand, abdominal pain is considered a symptom, as it is only something the patient can identify.
Prior to the 19th century, patients and physicians equally participated in the identification of signs and symptoms when there was a medical problem. As medical technology and diagnostic tests have advanced over the past 200 years however, identifying signs of an illness or disease became determined by the physician.
The advent of the percussion technique (tapping the chest wall and listening to the sounds), the stethoscope (listening to sounds of the heart and lungs), the spirometer (measuring lung function), the ophthalmoscope (examining the inside of the eye), and the use of x-ray machines, have all helped doctors to recognise medical signs in their patients more easily.
During the 20th century, there were countless new medical techniques and devices designed and created that helped to assess medical signs. These were all used and considered by doctors, not patients. It was during this time that the term sign became regarded as something a doctor noticed, and a symptom something recognised by the patient.
Medical signs are classified into the following categories.
Prognostic Signs: These are signs that point to the future. Prognostic signs indicate the outcome of the current state of the patient, rather than signifying the disease itself.
Anamnestic Signs: These are signs that point to the past. Anamnestic signs always point to the past, such as skin scars from acne previously in a person’s life.
Diagnostic Signs: These are signs that help a doctor recognise what is wrong with the patient.
Pathognomonic Signs: This is one step further than a diagnostic sign. A pathognomonic sign leaves little to no doubt that a disease is present in the patient.
A medical sign and a medical symptom are often used interchangeably. There are however, characteristically different. Simply stated, signs are what a doctor and patient both see, and a symptom is something a patient feels. A sign can be described as the definitive indication of a disease, while a symptom can be described as a characteristic of the disease.
A sign is typically considered the physical display of an illness, disease, or medical condition. A symptom or symptoms are what the patient experiences with the illness, disease, or medical condition. Where a patient usually notices the symptoms, it is often a doctor that will recognise the signs.
A medical sign is regarded as objective, meaning that they can be seen, heard, or felt. A symptom is regarded as subjective, meaning that they are not outwardly visible and are only recognised by the patient.