The Faces Pain Scale-Revised: toward a common metric in pediatric pain measurement.

The Faces Pain Scale (FPS; Bieri et al., Pain 41 (1990) 139) is a self-report measure used to assess the intensity of children's pain. Three studies were carried out to revise the original scale and validate the adapted version. In the first phase, the FPS was revised from its original seven faces to six, while maintaining its desirable psychometric properties, in order to make it compatible in scoring with other self-rating and observational scales which use a common metric (0-5 or 0-10). Using a computer-animated version of the FPS developed by Champion and colleagues (Sydney Animated Facial Expressions Scale), psychophysical methods were applied to identify four faces representing equal intervals between the scale values representing least pain and most pain. In the second phase, children used the new six-face Faces Pain Scale-Revised (FPS-R) to rate the intensity of pain from ear piercing. Its validity is supported by a strong positive correlation (r=0.93, N=76) with a visual analogue scale (VAS) measure in children aged 5-12 years. In the third phase, a clinical sample of pediatric inpatients aged 4-12 years used the FPS-R and a VAS or the colored analogue scale (CAS) to rate pain during hospitalization for surgical and non-surgical painful conditions. The validity of the FPS-R was further supported by strong positive correlations with the VAS (r=0.92, N=45) and the CAS (r=0.84, N=45) in this clinical sample. Most children in all age groups including the youngest were able to use the FPS-R in a manner that was consistent with the other measures. There were no significant differences between the means on the FPS-R and either of the analogue scales. The FPS-R is shown to be appropriate for use in assessment of the intensity of children's acute pain from age 4 or 5 onward. It has the advantage of being suitable for use with the most widely used metric for scoring (0-10), and conforms closely to a linear interval scale.