The quantification of pain: an analysis of words used to describe pain and analgesia in clinical trials.

In this study 116 subjects were asked to quantify the descriptive pain terms commonly used in analgesimetry by using the visual analog scale as a tool. The results showed highly variable responses. Several words that have been assigned the same value on an ordinal scale do not convey the same meanings as on the visual analog scale. The words some and terrible are probably the least useful terms to quantify pain. The word complete for describing pain relief showed the least variation. The data on global ratings varied greatly; 10% of the participants gave the same values to the terms very good and excellent. The unequal differences between descriptive terms that are commonly considered equidistant on an ordinal scale are clearly demonstrated. We propose an approach to quantifying pain that takes into account the interindividual variations in interpretation of descriptive pain terms.