Use of the functional assessment measure (FIM+FAM) in head injury rehabilitation: a psychometric analysis

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Abstract
OBJECTIVES The drive to measure outcome during rehabilitation after brain injury has led to the increased use of the functional assessment measure (FIM+FAM), a 30 item, seven level ordinal scale. The objectives of the study were to determine the psychometric structure, internal consistency, and other characteristics of the measure. METHODS Psychometric analyses including both traditional principal components analysis and Rasch analysis were carried out on FIM+FAM data from 2268 assessments in 965 patients from 11 brain injury rehabilitation programmes. RESULTS Two emergent principal components were characterised as representing physical and cognitive functioning respectively. Subscales based on these components were shown to have high internal consistency and reliability. These subscales and the full scale conformed only partially to a Rasch model. Use of raw item ratings, as opposed to transformed ratings, to produce summary scores for the two subscales and the full scale did not introduce serious distortion. CONCLUSION The full FIM+FAM scale and two derived subscales have high internal reliability and the use of untransformed ratings should be adequate for most clinical and research purposes in comparable samples of patients with head injury.