The Face Scale consists of a set of 6 faces that vary in the level of overt distress expressed.Subjects choose 1 face from the series of pain-expressing faces that best represents the current status of their pain.However,it is an ordinal scale that does not ensure equivalence for the differences between faces.
In this study,we conducted 2 experiments with the objective of evaluating the differences between faces and creating a pain scale that is easy to use in pain assessment.In experiment 1,the pain intensity evoked by 6 faces was measured using Scheffe’s method of paired comparisons,and each face was converted to a position within a 100-mm linear pain scale depending on the pain intensity.By doing this,we created a pain scale in the form of a Labeled Face Scale graduated at 0.00,10.02,18.61,40.31,62.22 and 100.00.In experiment 2,patients’pain was measured and compared using the Labeled Face Scale and a magnitude estimation method.Correlation analysis showed that there was a positive correlation between them (R
2=0.8127)and Bland-Altman analysis showed that the majority of plots (94.4%) fell within the coefficient of repeatability (±2 SD).
These results lead us to conclude that the Labeled Face Scale is a useful assessment tool for pain management.
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