Abstract:
Objectives: To evaluate the internal consistency of the Mayo-Portland Adaptability Inventory (MPAI), further refine the instrument, and provide reference data based on a large, geographically diverse sample of persons with acquired brain injury (ABI).

Participants: 386 persons with generally moderate-severe ABI.

Settings: Outpatient, community-based, and residential rehabilitation facilities for persons with ABI located in the U. S. West, Midwest and Southeast.

Methods: Rasch, item cluster, principal components, and traditional psychometric analyses for internal consistency of MPAI data and subscales.

Results: With rescoring of rating scales for four items, a 29-item version of the MPAI
showed satisfactory internal consistency by Rasch (Person Reliability = .88; Item Reliability = .99) and traditional psychometric indicators (Cronbach.s alpha = .89). Three rationally derived subscales for Ability, Activity and Participation demonstrated psychometric properties that were equivalent to subscales derived empirically through item cluster and factor analyses. For the three subscales, Person Reliability ranged from .78 to .79; Item Reliability, from .98 to .99; and Cronbach.s alpha, from .76 to .83. Subscales correlated moderately (Pearson r = .49 to .65) with each other and strongly with the overall scale (Pearson r = .82 to .86).

Conclusions: Outcome after ABI is represented by the unitary dimension described by the MPAI. MPAI subscales further define regions of this dimension that may be useful for evaluation of clinical cases and program evaluation.