Objectives: To evaluate the internal consistency, inter-rater agreement, concurrent validity and floor/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 ABI undergoing evaluation, significant others (SO), 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 inter-rater agreement.
Setting: Outpatient rehabilitation in academic PM&R Department.
Participants: 134 people with ABI consecutively seen for evaluation, SO, and evaluating staff.
Main Outcome Measures: MPAI, M2PI
Results: The M2PI demonstrates satisfactory internal consistency, concurrent validity, inter-rater agreement, and minimal floor and ceiling effects although evidence of rater bias is also apparent. Composite indices demonstrate more desirable psychometric properties than ratings by individual rater groups.
Conclusion: 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 ABI, SO, and staff.