Prediction of Functional Outcome in Post-Hospital Brain Injury Rehabilitation

Post-hospital brain injury rehabilitation programs are afforded limited time to reduce chronic disability resulting from acquired brain injury. Therefore, the purpose of this study was to identify deficit areas resulting from acquired brain injury that have the greatest impact on functional outcomes to enable greater efficiency in rehabilitation programming. Study participants were 1717 persons with acquired brain injury treated in residential post-hospital rehabilitation programs. Participants were assessed at admission and discharge on the MPAI-4. Functional status at discharge was evaluated based on T-scores derived from MPAI-4 discharge participation index items: initiation, self-care and residence. The database of 1717 was randomly divided into two subsets. Items from admission Abilities Index and select person variables were entered into stepwise multiple regression on subset one and then in a hierarchical multiple regression on subset two. Rash analysis demonstrated satisfactory construct validity and internal consistency of admission and discharge MPAI-4 evaluations (Person reliability ≥ 0.90, Item reliability = 0.99). Both regression analyses revealed that Mobility and Novel Problem Solving accounted for 40% of the variance in functional outcome, p < 0.001. Acquired brain injury results in a myriad of cognitive and physical impairments. Of the many possible deficits, the greatest gains in overall functional outcomes may be achieved by allocating additional treatments aimed at reducing disability in mobility and novel problem solving.

improve the overall health status of persons who have experienced an acquired brain injury. A brain injury, whether traumatic or non-traumatic, disrupts normal brain functions resulting in enduring impairment to cognition, communication, mobility and emotional well-being [1]. A brain injury is a chronic condition with an indefinite period of time required to regain or improve function [2].
Current research suggests that with comprehensive multidisciplinary rehabilitation, survivors can realize significant reduction in disability well over a year after injury [3] [4] [5] [6]. However, the majority of specialized brain injury rehabilitation services is accessed from a hospital system and concludes within approximately 2 -3 months following injury [7]. The need for continued rehabilitative care has resulted in post-hospital services being developed with the purpose of continued restoration of independence over a gradual period of time providing appropriate medical, behavioral, and social supports to sustain and enhance quality of life [7]. Unfortunately, funding for this level of treatment is limited, with only a minority of those in need having access to this care [1]. With limited financial resources allocated for post-hospital brain rehabilitation, it is critical that these programs utilize evidenced based best practice in order to maximize efficiency and effectiveness in achieving positive outcomes. Best practices that shorten the length of treatment time while obtaining meaningful reduction in disability can extend existing resources which may be utilized for others in need.
One approach to developing such best practices is to identify those impairment areas that have the greatest impact on outcome. This would enable a more focused approach to rehabilitative care in which those deficits having the greatest impact on functional independence would be apportioned more frequent treatments of longer duration. Therefore, the purpose of this study was to identify functional deficits that have the greatest impact on outcome following acquired brain injury.

Subjects
Participants for the study were selected from a database consisting of 3511 neurologically impaired persons with consecutive discharges from 32 residential and nonresidential post-hospital rehabilitation programs in 24 states from 2011-2018. All programs were part of a network of care for brain injured individuals. These programs included active neurorehabilitation (residential physical and cognitive rehabilitation), neurobehavioral intensive (residential rehabilitation emphasizing reduction of physical and verbal aggression), day treatment (non-residential physical and cognitive rehabilitation) and supported living (long-term residential care emphasizing quality of life). For a detailed description of each of these programs see Lewis and Horn, 2015 [5]. From this inclusive database, 1717 met study inclusion criteria: age ≥ 18, diagnosis of acquired brain injury and treated in residential neurorehabilitation programs with a minimum The demographic characteristics of the study sample are presented in Table 1.

Procedure
Participants were evaluated upon admission by each program's multidisciplinary

Analysis
Rasch analysis was performed to determine reliability of MPAI-4 admission and discharge assessments and the goodness of fit for dependent variables used in regression analyses.

Construct Validity
Construct validity refers to the extent to which an evaluation tool measures the underlying construct that it is intended to measure. Rasch fit statistics accomplish this by evaluating expected values for an item to the actual value obtain from the data set. Fit statistics also provide an estimate of the distinct contribution for each item in describing the underlying construct and the extent to which they differentiate among people along the continuum of that construct [10]. As suggest that high levels of limitation are observed when low levels would be expected for that person on those items. Values greater than 1 indicate that there is more noise or random variation on an item than would be expected. Fit values falling between 0.5 and 1.5 are considered productive for measurement use [11].
Items that fall outside those parameters may not reliably represent the latent construct being measured.

Reliability
Reliability refers to the consistency of a measure or the extent to which a meas-

Prediction
Multiple regression analyses were conducted to identify a predictive model for outcomes following post-hospital residential brain injury rehabilitation. The variables of interest included physical and cognitive functions measured by the MPAI-4 Abilities Index and three person variables: age, length of stay in program, and chronicity (onset of injury to admission).

Dependent Variable
In this study, functional outcome was measured using the following three ordinal variables from the MPAI-4 participation index: initiation, self-care, and residence (home and community skills). These variables were selected because they are fundamental to independent functioning: the ability to react appropriately to

Independent Variables
Variables on the Abilities Index, which provide measures of frontal lobe functioning, were entered as predictor variables in the multiple regression analyses.
Each of these variables measure frontal lobe functions that are at the highest level of cognitive processing requiring interaction of multiple systems to produce physical, behavioral, and communication functioning to meet daily challenges [14] [15]. Table 2 lists these variables along with a brief description of each.

Multiple Regression Analyses
Stepwise multiple regression was the primary method used to identify the best set of predictor variables from those listed in Table 2. The stepwise multiple regression analysis searches for predictive relationships within a data set but is prone to overestimation of the statistical significance between variables yielding results that may be sample dependent (Type 1 error). To reduce this risk, the data set was randomly divided into two independent sub-groups using SPSS ver-

Reliability
Rasch person reliability coefficients were 0.90, and 0.94 respectively for admission and discharge assessments. These reliability coefficients exceeded the acceptable standard of 0.80 for person reliability and indicated the MPAI-4 effectively discriminated among those along the disability continuum.  Item reliability coefficients were 0.99 at each assessment period. These are considered strong reliability coefficients. Therefore, the results suggested that for both assessment periods the items across the disability continuum were stable.
There was a high level of agreement in identifying easy through difficult items.
These values indicate that the MPAI-4 revealed three performance strata (e.g. low, medium, and high disability) at both admission and discharge. The item separation values for both assessment periods exceeded 3.00 indicating a consistent item hierarchy from least difficult to most difficult. Specific item separation values were 22.90 (admission) and 25.31 (discharge). Based on the results, there was sufficient item and person separation for purposes of the analysis.

Prediction
A step-wise multiple regression conducted on 891 of the total sample (n = 1717) identified a predictive model with five functional variables (mobility, novel problem solving, non-verbal communication, fund of information, and use of hands) and one demographic variable (chronicity), R 2 = 0.45, F(6,885) = 137.95, p < 0.0001 (adjusted R 2 = 0.44). Of those variables, Mobility predicted the largest portion of variance in functional outcome (adjusted R 2 = 0.26). Novel problem solving at admission increased the prediction 14%. The remaining three functional variables contributed an additional 4% to the prediction of outcome. Chronicity with a significant beta weight of 0.08 (p < 0.01) added less than 1% to the model. The validation hierarchical regression conducted on a second subsample (n = 831) with those six variables entered was also significant (R 2 = 0.45, F(6,826) = 106.46, p < 0.0001, adjusted R 2 = 0.44). Again mobility and novel problem solving at admission were the strongest predictors. Age and length of stay were not significant in either of the regression analyses. Table 4 displays the predictive findings for the analyses.

Discussion
For the majority of patients with acquired brain injury, rehabilitative treatment occurs within a hospital system [7]. Unfortunately many leave the hospital system with chronic disabilities requiring supervision and physical assistance [4] [19]. Over the past 30 years a system of post-hospital rehabilitative care, both residential and nonresidential, has emerged. Substantial research shows the efficacy of this level of care for continuing the reduction of disability that begins in the hospital system [3] [20] [21] [22]. However, limited funding for this specialized care creates the need for evidenced based rehabilitation to further improve treatment efficiency and effectiveness [1]. Targeted treatment may lead to cost effective care with improved access in order to reduce disability.
As in all areas of health care, improving treatment efficacy requires an understanding of disability through the use of accurate, reliable and comprehensive assessment tools. The MPAI-4 meets these requirements. The MPAI-4 assesses 29 areas of disability and has undergone extensive psychometric testing [9]. In the present study, the MPAI-4 admission and discharge assessments exceeded Rasch standards for reliability and validity.
Improving clinical practice also requires identification of variables that have the greatest influence on functional outcome. More importantly research findings need to help clinicians focus efforts directly into skills that have the greatest impact on variables that change a person's level of function and need for assistance. In the present study, functional outcome was determined at discharge by a T-score comprised of three MPAI-4 Participation items: Initiation (the ability to initiate and inhibit responses effectively), Self-Care (the ability to manage personal hygiene), and Residence (the ability to function in the home and community safely and efficiently). Previous research by Lewis and Horn [5] identified these as important determinants of societal participation following brain injury.
To better understand how to effect these important variables, the study focused on physical and cognitive contributions from the MPAI-4 Abilities Index. These variables were entered into the multiple regression analyses for prediction of outcome. In two separate regression analyses, the following 5 MPAI-4 Abilities items were revealed to be most influential for positive outcomes related to so- Thus the finding that these two items accounted for 40% of overall outcome is F. D. Lewis, G. J. Horn Journal of Behavioral and Brain Science not surprising. The findings provide a foundation for being prescriptive with post-hospital rehabilitation, namely, targeting deficit areas that impact disability reduction regardless of injury severity.

Conclusion
Meaningful best practice employs the translation from retrospective to prospective controlled studies that replicate the current findings and identify optimal treatment frequency and duration based on this model. The results of this study establish a basis for prospective controlled research that can lead to a prescriptive approach to post-hospital brain injury rehabilitation. The goal with the prescriptive approach is evidence-based targeted care with improved outcomes and cost management for greater accessibility for those injured. Two separate regression analyses revealed that 40% of rehabilitative outcome was attributed to Mobility and Novel Problem Solving. Targeting these functions with additional treatment frequency and duration would likely result in an increase in patient independence at discharge.