CALLAHAN, AustraliaA new study suggests that the Faces Pain Scale (FPS) is sensitive and discriminating for use in evaluating pain in young children, but does not function as a truly linear scale. Children in the study had difficulty discriminating among Faces 3, 4, and 5 and between Faces 5 and 6, said Mark Hunter, PhD, of the Department of Psychology, University of Newcastle.
Testing of the FPS by its developers (Bieri et al Pain 41:139-150, 1990) in a large sample of school children aged 6 to 9 showed that the scale is discriminating, but that age level affects the response, Dr. Hunter said, with younger children being more variable in their accuracy.
Dr. Hunter and his colleagues at the University of Newcastle and the Department of Pediatrics, John Hunter Hospital, New Lambton, tested the FPS in 135 younger children divided into three age groups: age 3.5 to 4.5 years, age 4.5 to 5.5 years, and age 5.5 to 6.5 years.
The FPS is made up of seven cards each showing a schematic face and conveying increasing levels of pain intensity, from no pain for Face 1 up to severe pain for Face 7 (see Figure).
Before each test, the researchers spent a few minutes with the child to establish rapport and ascertain the childs understanding of the concept of pain (the childs pain language, which was used throughout the testing).
The researchers administered the test in three different ways to 30 children from each age group. (The other 15 children in each group participated in a test-retest reliability study.)
1. All seven cards were laid out randomly on the desk, and the child was asked to put the faces in order of pain expression from least to most.
2. The child was shown all possible pairs of cards, one pair at a time, and asked which face in the pair showed more pain.
3. The child was given 12 blocks. The researcher placed Face 1 on the desk and explained that the first face got no blocks because it showed no pain. The researcher then gave Face 7 six blocks, explaining that this number of blocks represented the worst pain possible. Then the remaining five cards were placed randomly in front of the child who was asked to give each face the number of blocks needed for the pain shown on the face.
The objective of this task, the researchers said, was to see if the children recognized the implicit linearity of the scale by correctly placing one block in front of Face 2, two blocks in front of Face 3, and so on.
In the first test, Dr. Hunter said, the extremes of the faces continuum were placed with almost complete accuracy by all age groups. The children did have some difficult with positioning Faces 3, 4, and 5. The children in the two youngest age group placed Face 5 at the greatest distance from its correct order, while those in the oldest group had the most difficulty with Face 6.
In the second test, the youngest age group made more errors than the other two, the researchers said (J Pain Symptom Manage 20:122-129, 2000).
In the third test, all three age groups showed deviations in the number of blocks they placed in front of the faces from the implied correct number of blocks, with the youngest children doing the worst. These results suggest caution in interpreting the Faces Scale as a linear scale, at least for very young children, Dr. Hunter said.
The findings, the investigators said, indicate that the FPS is a scale that even the very young can understand and use appropriately, and one with which children are able to discriminate levels of pain in a consistent fashion. However, they noted that question marks remain over the discriminability of Faces 5 and 6 and over the accuracy of the estimates of very young children.