Validation of self-report pain scales in children

Abstract

Background and objectives: The Faces Pain Scale-Revised (FPS-R) and Color Analog Scale (CAS) are self-report pain scales commonly used in children but insufficiently validated in the emergency department setting. Our objectives were to determine the psychometric properties (convergent validity, discriminative validity, responsivity, and reliability) of the FPS-R and CAS, and to determine whether degree of validity varied based on age, sex, and ethnicity.

Methods: We conducted a prospective, observational study of English- and Spanish-speaking children ages 4 to 17 years. Children with painful conditions indicated their pain severity on the FPS-R and CAS before and 30 minutes after analgesia. We assessed convergent validity (Pearson correlations, Bland-Altman method), discriminative validity (comparing pain scores in children with pain against those without pain), responsivity (comparing pain scores pre- and postanalgesia), and reliability (Pearson correlations, repeatability coefficient).

Results: Of 620 patients analyzed, mean age was 9.2 ± 3.8 years, 291(46.8%) children were girls, 341(55%) were Hispanic, and 313(50.5%) were in the younger age group (<8 years). Pearson correlation was 0.85, with higher correlation in older children and girls. Lower convergent validity was noted in children <7 years of age. All subgroups based on age, sex, and ethnicity demonstrated discriminative validity and responsivity for both scales. Reliability was acceptable for both the FPS-R and CAS.

Conclusions: The FPS-R and CAS overall demonstrate strong psychometric properties in children ages 4 to 17 years, and between subgroups based on age, sex, and ethnicity. Convergent validity was questionable in children <7 years old.

Keywords: Color Analog Scale (CAS); Faces Pain Scale–Revised (FPS-R); age; emergency department; ethnicity; language; pain; pain scale; pediatric; race; reliability; sex; validity.

Figures

FIGURE 1

Left: Faces Pain Scale - Revised (FPS-R), 2001, International Association for the Study of Pain. Reproduced with permission from Hicks CL et al. Pain. 2001;93:176. See www.iasp-pain.org/FPSR. Right: Color Analog Scale (CAS). Reproduced with permission from McGrath PA et al. Pain. 1996;64(3):439.

FIGURE 2

Bland Altman Plot of initial FPS-R and CAS for children with painful and nonpainful conditions. The plot represents the number of children (represented by square size) who have a certain difference between initial FPS-R and CAS scores, plotted against the average of the child’s FPS-R and CAS scores. The horizontal lines immediately above and below 0 represent the predetermined limits of agreement (±2/10). If a difference is outside the predetermined limits, it indicates poor agreement between the FPS-R and CAS.

FIGURE 3

Proportion of children with a difference of more than 2 of 10 between initial FPS-R and CAS scores. Groups that have a proportion >20% have poor agreement. The younger and older age groups consist of children 4 to 7 years old, and 8 to 17 years old, respectively.

FIGURE 4

Proportion of children with a difference of more than 2 out of 10 between initial FPS-R and CAS scores based on severity of pain. Severity of pain obtained by averaging FPS-R and CAS scores.

FIGURE 5

FPS-R and CAS scores before and after analgesia administration in children with painful conditions.

FIGURE 6

Absolute maximum differences in pre- and postanalgesic scores in children who report their pain as being “about the same,” before and after receiving analgesia.