Measurement of subjective phenomena in primary care research: the Visual Analogue Scale.

The visual analogue scale is a technique used to measure subjective phenomena. It is a self-reporting device consisting of a line of predetermined length that separates extreme boundaries of the phenomenon being measured. The purpose of this review is to report on the characteristics of the visual analogue scale technique, including its reliability, validity, accuracy, and scale value. This review presents several examples of the usefulness of the visual analogue scale technique in primary care research projects, describes its advantages and limitations, and presents suggestions for constructing visual analogue scales.