Psychometric Properties and Sex Differences on the Mayo-Portland Adaptability Inventory Participation Subscale (M2PI) in Veterans With Traumatic Brain Injury

Objective: To evaluate the structural validity of the Mayo-Portland Adaptability Inventory Participation Index (M2PI) in a sample of veterans and to assess whether the tool functioned similarly for male and female veterans.

Design: Rasch analysis of M2PI records from the National Veterans Traumatic Brain Injury Health Registry database from 2012-2018.

Setting: National VA Polytrauma System of Care outpatient settings.

Participants: Veterans with a clinically confirmed history of traumatic brain injury (TBI) (N=6065; 94% male).

Interventions: Not applicable.

Main outcome measures: M2PI, a 5-point Likert-type scale with 8 items. For this analysis, the 2 employment items were treated individually for a total of 9 items.

Results: The employment items misfit the Rasch Measurement model (paid employment mean square [MnSq]=1.40; other employment MnSq=1.34) and were removed from subsequent iterations. The final model had eigenvalue 1.87 on the first contrast, suggesting unidimensionality of the remaining 7 items. Item order from least to most participation restriction was transportation, self-care, residence management, financial management, initiation, leisure, and social contact. Wright's person separation reliability for nonnormal distributions was 0.93, indicating appropriateness of M2PI for making individual-level treatment decisions. Mean person measure was -0.92±1.34 logits, suggesting that participants did not report restrictions on most items (item mean=0 logits). A total of 3.8% of the sample had the minimum score (no impairment on all items), and 0.2% had the maximum score. Four items had different item calibrations (≥0.25 logits) for female compared with male veterans, but the hierarchy of items was unchanged when the female sample was examined separately.

Conclusions: These findings suggest that, although employment is a poor indicator of participation restrictions among veterans with TBI, the M2PI is unidimensional. Because of subtle differences in scale function between male and female participants, M2PI should be part of a more thorough clinical interview about participation strengths and restrictions.