The Mayo-Portland Participation Index: A brief and psychometrically sound measure of brain injury outcome

Objective: To evaluate the internal consistency, interrater agreement, concurrent validity, and floor and ceiling effects of the 8-item Participation Index (M2PI) of the Mayo-Portland Adaptability Inventory (MPAI). Design: M2PI data derived from MPAIs completed independently by the people with acquired brain injury undergoing evaluation, their significant others, and rehabilitation staff were submitted to Rasch Facets analysis to determine the internal consistency of each independent rater group and of composite measures that combined rater groups. Correlations with the full-scale MPAI were examined to assess concurrent validity, as was interrater agreement. Setting: Outpatient rehabilitation in academic physical medicine and rehabilitation department. Participants: People with acquired brain injury (N=134) consecutively seen for evaluation, significant others, and evaluating staff. Interventions: Not applicable. Main Outcome Measures: The MPAI and M2PI. Results: The M2PI showed satisfactory internal consistency, concurrent validity, interrater agreement, and minimal floor and ceiling effects, although evidence of rater bias was also apparent. Composite indices showed more desirable psychometric properties than ratings by individual rater groups. Conclusions: The M2PI, particularly in composite indices and with attention to rater biases, provides an outcome measure with satisfactory psychometric qualities and the potential to represent the varying perspectives of people with acquired brain injury, significant others, and rehabilitation staff.