Pain-meter Systems

Since pain is a subjective experience, measuring its levels is not an easy task and can only be done indirectly. Assessment is carried out by collecting information reported by the person who suffers from pain. Methods for measuring pain are therefore based on subjective, or perceived, data:

Self-reported description of the painful sensation.
The level of suffering accompanying the pain.
Behavior associated with the pain.

There are two ways of measuring pain:

Physical. This concerns certain pain features such as location, extent, and accompanying symptoms.
Functional. This measures the degree of debilitation the pain causes. It evaluates physical (walking, exertion, etc.), verbal and social abilities (work, recreational activities, etc.).

Both types of assessment are carried out by a physician based on what the patient reports.

Several methods to evaluate and measure pain have been developed. They usually involve questionnaires a doctor asks a patient to complete. Questionnaires vary, but the main types used are:

Pain intensity rating scales. These can be numeric or verbal. With numeric versions, the patient is asked to assign a value to the pain on a scale from 0 (no pain) to 10 (the worst imaginable pain). With verbal versions, the severity of the pain is characterized by an adjective that describes its intensity on a scale:
absent - mild - moderate -severe. Each scale is then correlated to a corresponding assessment scale of pain relief.
Facial expression scale. Normally used with children. Pain intensity is associated with a series of diagrams of facial expressions that the child selects.
Pain map. Used to locate the site of pain. The patient is asked to mark on a drawing of a human figure the spot or general area where he or she feels pain.
Pain diary. This is especially useful in cases of chronic or recurrent pain. The patient notes the pain features (intensity, duration, etc.) in relation to activities (work, sleep, daily living activities, taking medication, etc.)