'Less is more': validation with Rasch analysis of five short-forms for the Brain Injury Rehabilitation Trust Personality Questionnaires (BIRT-PQs).

BACKGROUND

Previous analyses demonstrated a lack of unidimensionality, item redundancy, and substantial administrative burden for the Brain Injury Rehabilitation Trust Personality Questionnaires (BIRT-PQs).

OBJECTIVE

To use Rasch Analysis to calibrate five short-forms of the BIRT-PQs, satisfying the Rasch model requirements.

METHODS

BIRT-PQs data from 154 patients with severe Acquired Brain Injury (s-ABI) and their caregivers (total sample = 308) underwent Rasch analysis to examine their internal construct validity and reliability according to the Rasch model.

RESULTS

The base Rasch analyses did not show sufficient internal construct validity according to the Rasch model for all five BIRT-PQs. After rescoring 18 items, and deleting 75 of 150 items, adequate internal construct validity was achieved for all five BIRT-PQs short forms (model chi-square -values ranging from 0.0053 to 0.6675), with reliability values compatible with individual measurements.

CONCLUSIONS

After extensive modifications, including a 48% reduction of the item load, we obtained five short forms of the BIRT-PQs satisfying the strict measurement requirements of the Rasch model. The ordinal-to-interval measurement conversion tables allow measuring on the same metric the perception of the neurobehavioral disability for both patients with s-ABI and their caregivers.