An Examination of the Factor Structure of the Neonatal Facial Coding System and the Modified Behaviour Pain Scale

Diverse behavioural cues have been proposed to be useful indicators of infant pain, but there is a paucity of evidence based on formal psychometric evaluation to establish their validity for this purpose. We aimed to examine two widely-used pain scales, the Neonatal Facial Coding System (NFCS) and the Modified Behaviour Pain Scale (MBPS), by examining their factor structures with factor analysis. The results indicated that an item reduced NFCS scale with three items produced a one-factor pain model that maintained the good psychometric properties of the 7-item scale. In addition, it was found that MBPS also has challenging internal consistency, with items that are weakly correlated and highly redundant. Redefinition of MBPS with a single indicator was suggested. This analysis provides new iterations of NFCS and MBPS that improve construct validity and internal consistency. These versions also increase the feasibility of both measures and improve their potential for clinical use.