Development and Validation of a Tool to Assess Pain in Preverbal and Non-verbal Children with Cerebral Palsy: Cerebral Palsy Faces Pain Scale (CPFPS)

Background: Cerebral palsy (CP) is the most common neurodisability in children. This study aimed to develop and validate a faces pain scale for preverbal and non-verbal children (PvNv) with CP in Nigeria. Methods: Twelve paediatric practitioners and three verbal adults with CP participated in a three-round modified Delphi study on scale development and validation of the CPFPS. Data from the scale development were analysed using the items content validity index (I-CVI) and scale content validity (S-CVI). The concurrent validity of CPFPS was established using the University of Wisconsin Children's Hospital Pain Scale (UWHPS) for PvNv children. Results: Facial characteristics such as furrowing, crying, clenching and grinding of teeth, quivering lips, and changes in the eye may indicate pain in PvNv CP. These features have I-CVI scores of 1.00, 1.00, 0.83, 0.83, and 0.83, respectively. Moreover, the "eye/furrow" and "mouth/nasolabial" features were identified as sub-scales with S-CVI scores of 1.00 and 0.83, respectively, while the CPFPS received an S-CVI score of 0.89. A significant positive correlation was observed between CPFPS and the UWHPS (ρ=0.949; p = 0.001) (concurrent validity). CPFPS also exhibited high inter-rater reliability (ICC=0.994, 95% CI=0.988-0.997). However, the known-group validity of the CPFPS with age, CP types and functional status were non-significant (p>0.05), except for the communication ability of children with CP (ρ=0.233; p=0.022). Conclusions: CPFPS, a pain assessment tool using "eye/furrow" and "mouth/nasolabial" features, is reliable for evaluating pain in PvNv children with CP in Nigeria. Our results confirm the initial validity and reliability of the CPFPS, but further investigations into the evaluation of other psychometric properties are needed.