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Evaluating the Statistical Properties of the Pain Interference Index in Children and Adolescents with Chronic Pain

&NA; The high prevalence of chronic debilitating pain in pediatric populations calls for more knowledge regarding the impact of pain on functioning or pain interference. This in turn requires valid and reliable instruments to adequately assess the impact of pain on functioning. Also, adequate measures of pain interference are important in evaluations of behavioral interventions aimed at improving functioning. Objective: The objectives of this study were to evaluate the statistical properties of the Pain Interference Index (PII), including the factor structure, internal consistency, and concurrent criteria validity of the instrument. Method: Data were collected from a consecutive sample of children and adolescents referred to a tertiary pain clinic due to chronic pain (n = 163). A principal component analysis was used to investigate the latent factor structure of items. The internal consistency was assessed by Cronbach's alpha. A set of hierarchical regression analyses was conducted to evaluate the ability of instruments to predict levels of depression and functional disability. Results: Analyses indicated the adequacy of a 1-factor solution with a total of 6 items. The intercorrelation between items and the scale's reliability was satisfactory. Furthermore, bivariate correlations and hierarchical regression analyses illustrate the concurrent criteria validity of the instrument. Conclusion: Results support the use of PII as an adequate instrument to assess pain interference in children and adolescents with chronic pain.