The McGill Pain Questionnaire is the most widely used and popular in evaluating pain. It evaluates three major classes of word descriptions - sensory, affective, and evaluative - that patients use to specify their subjective pain experience.

It has a built-in intensity scale. Multiple reports in the literature have evaluated this method of pain measurement, and it has been used extensively in clinical evaluation and treatment trials.

Experts believe it provides a quantity of information that can be treated statistically, and that it is sufficiently sensitive to detecting differences in effectiveness among pain relief treatments. Although physiological techniques such as measurement of cortical evoked potentials, muscle tension, vasodilation, heart rate, and blood pressure have a firm scientific basis in the measurement of acute pain in the laboratory, they have not been scientifically evaluated in the clinical or chronic pain setting.

Behavioral measurements of pain are logical techniques for measuring pain, since people in pain must engage in behavior indicative of their state. Most behavior measurement techniques use three categories of behavior: somatic intervention, impaired functional capacity, and pain complaints.

The University of Alabama Behavioral Measurement of Pain Scale is based on 10 behaviors such as vocalization and the frequency of intensity of these expressions. Although interobserver reliability is good, many trained observers and many observations are needed to obtain accurate and valid information.

Clearly, there is at present no ideal method for evaluating and measuring chronic pain and the effectiveness of treatment techniques. Those measurements that reflect subjective, physiological and behavioral components with independent and direct monitoring are the most appropriate.

Behavioral indices may assume greater importance as chronicity increases, since the question of how much the patient is able to do rather than how much it hurts may be the more important question in a chronic pain management setting. This is especially true when considering the cost-effectiveness of pain management programs, since functional outcome is often more important to third party payers than perceived level of pain.