Brain Injury Sense of Self Scale: psychometric development of a new measure of strength of self-identity after traumatic brain injury.

Abstract

Background: There is growing awareness that traumatic brain injury (TBI) can have a significant and troublesome impact of a person's self-identity, yet few measurement tools exist to clinically evaluate this.

Aim: The aim of this paper was to develop a patient-reported measure of strength of self-identity after TBI - the Brain Injury Sense of Self Scale (BISOSS).

Design: Measurement development and validation.

Setting: UK and New Zealand communities.

Population: One hundred and thirty-six people with TBI (68.4% [93/136]) male; mean age 47.9 years, SD 13.0 years; mean time post-TBI 11.2 years, SD 11.1 years; 74.3% (101/136) moderate to severe TBI).

Methods: Preliminary measurement items were generated from prior qualitative research, a concept analysis, and cognitive interviewing with survivors of TBI. Administration of the draft BISOSS, the Glasgow Outcome Scale, and the Sense of Coherence Scale to participants - with factor analysis, Rasch analysis, and construct validity testing to refine and test the draft BISOSS.

Results: After iterative refinements using the Rasch model to help guide item adjustments, BISOSS was comprised of three subscales (egocentric self, sociocentric self, and relational self), each which fit the Rasch model and demonstrated unidimensionality, adequate precision, absence of differential item functioning and adequate person separation index. BISOSS scores correlated well with employment status, leisure activities and positive family relationships. Participants' responses supported the notion that problems with self-identity were commonplace after TBI, with 40% of respondents self-reporting such problems.

Conclusions: BISOSS is a valid measure, which conforms to measurement expectations for an interval scale and is in grounded in the language of people with TBI. It is now available as a validated tool for assessing self-identity issues post-TBI. Further work is required to assess whether the scale can change over time or is responsive to interventions targeted at strengthening self-identity.

Clinical rehabilitation impact: Change in self-identity is a commonplace problem following TBI but is seldomly evaluated in clinical practice. BISOSS can be used to explore patient experiences of problems with self-identity after TBI and will help further our understanding of this phenomenon.