Signs and symptoms: Definition, importance, and uses

Many people use the words ‘sign’ and ‘symptom’ interchangeably. However, there are important differences that affect their use in the field of medicine.

Any objective evidence of a disease, such as a skin rash or a cough, is a sign. A doctor, family members, and the individual experiencing the signs can identify these.

However, less obvious breaks in normal function, such as stomachache, lower back pain, and fatigue, are symptoms and can only be recognized by the person experiencing them. Symptoms are subjective, meaning that other people only know about them if informed by the individual with the condition.

This MNT Knowledge Center article will look at the implications of signs and symptoms as well as their history. The piece will also introduce the different types of sign and symptom and their uses in medicine.

Fast facts on signs and symptoms

A light headache can only ever be a symptom because no one else can observe it.

Medical symptoms are split into chronic, relapsing, and remitting.

An example of a medical sign is high blood pressure, as it can be measured and observed by another person.

Anthony van Leuwenhoek invented the microscope in 1674, forever changing the face of diagnostic tools.

Sign vs. symptom

Rash on back
A sign is the effect of a health problem that can be observed by someone else. A symptom is an effect noticed and experienced only by the person who has the condition.

The key difference between signs and symptoms is who observes the effect.

For example, a rash could be a sign, a symptom, or both:

If the patient notices the rash, it is a symptom.

If the doctor, nurse, or anyone other than the patient notices the rash, it is a sign.

If both the patient and doctor notice the rash, it can be classed as both a sign and a symptom.

Regardless of who notices that a system or body part is not functioning normally, signs and symptoms are the body’s ways of letting a person know that not everything is running smoothly. Some signs and symptoms need follow-up by a medical professional, while others may completely resolve without treatment.

Stethoscope in use on little girl
Advancing technology has put more power in the hands of clinicians when it comes to identifying diseases.

Since the 1800s, medical science has come on leaps and bounds in helping physicians clearly identify signs. A range of devices is now available to help doctors identify and analyze signs that even the patient may not have recognized.

These include:

Stethoscope: A doctor can use this to listen to the sounds of the heart and lungs.

Spirometer: This helps to measure lung function.

Ophthalmoscope: An eye specialist may use this to examine the inside of the eye.

X-ray imaging: This can show damage to the bones.

Sphygmomanometer: This is a device that fits around the arm and measures blood pressure.

During the 20th century, hundreds of new devices and techniques were created to evaluate signs. It was during this period in modern medical history that the terms “sign” and “symptom” developed separate meanings, as doctors and patients no longer needed to work together as closely to identify medical issues.

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