Rasch Analysis, Dimensionality, and Scoring of the Neuropsychiatric Inventory (NPI) Irritability and Aggression Subscales in Individuals with Traumatic Brain Injury

Publication date: Available online 14 September 2017
Source:Archives of Physical Medicine and Rehabilitation
Author(s): James F. Malec, Timothy E. Stump, Patrick O. Monahan, Jacob Kean, Dawn Neumann, Flora M. Hammond
ObjectiveTo develop, for versions completed by individuals with traumatic brain injury (TBI) and an observer, a more precise metric for the Neuropsychiatric Inventory (NPI) Irritability and Aggression scales using all behavioral item ratings for use with individuals with TBI and address the dimensionality of the represented behavioral domains.DesignRasch and confirmatory factor analyses of retrospective baseline NPI data from three treatment studies.SettingPostacute rehabilitation clinic.Participants287 cases with observer ratings; 238 cases with self-ratings by participants with complicated mild, moderate or severe TBI at least 6 months post-injury.Main Outcome MeasureFrequency and severity ratings from NPI Irritability/Lability and Agitation/Aggression subscales.ResultsConfirmatory factor analyses of both observer and participant ratings showed good fit for either a one-factor or two-factor solution. Consistent with this, the Rasch model also fit the data well with aggression items indicating the more severe end of the construct and irritability items populating the milder end.ConclusionsIrritability and aggression appear to represent different levels of severity of a single construct. The derived Rasch metric offers a measure of this construct based on responses to all specific items that is appropriate for parametric statistical analysis and may be useful in research and clinical assessments of individuals with TBI.



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