A prediction model of military combat and training exposures on VA service-connected disability: a CENC study.

Background: Research has shown that number of and blast-related Traumatic Brain Injuries (TBI) are associated with higher levels of service-connected disability (SCD) among US veterans. This study builds and tests a prediction model of SCD based on combat and training exposures experienced during active military service.Methods: Based on 492 US service member and veteran data collected at four Department of Veterans Affairs (VA) sites, traditional and Machine Learning algorithms were used to identify a best set of predictors and model type for predicting %SCD ≥50, the cut-point that allows for veteran access to 0% co-pay for VA health-care services.Results: The final model of predicting %SCD ≥50 in veterans revealed that the best blast/injury exposure-related predictors while deployed or non-deployed were: 1) number of controlled detonations experienced, 2) total number of blast exposures (including controlled and uncontrolled), and 3) the total number of uncontrolled blast and impact exposures.Conclusions and Relevance: We found that the highest blast/injury exposure predictor of %SCD ≥50 was number of controlled detonations, followed by total blasts, controlled or uncontrolled, and occurring in deployment or non-deployment settings. Further research confirming repetitive controlled blast exposure as a mechanism of chronic brain insult should be considered.

Utility of post-traumatic amnesia in predicting 1-year productivity following traumatic brain injury: comparison of the Russell and Mississippi PTA classification intervals.

BACKGROUND: Duration of post-traumatic amnesia (PTA) correlates with global outcomes and functional disability. Russell proposed the use of PTA duration intervals as an index for classification of traumatic brain injury (TBI) severity. Alternative duration-based schemata have been recently proposed as better predictors of outcome to the commonly cited Russell intervals. OBJECTIVE: Validate a TBI severity classification model (Mississippi intervals) of PTA duration anchored to late productivity outcome, and compare sensitivity against the Russell intervals. METHODS: Prospective observational data on TBI Model System participants (n=3846) with known or imputed PTA duration during acute hospitalisation. Productivity status at 1-year postinjury was used to compare predicted outcomes using the Mississippi and Russell classification intervals. Logistic regression model-generated curves were used to compare the performance of the classification intervals by assessing the area under the curve (AUC); the highest AUC represented the best-performing model. RESULTS: All severity variables evaluated were individually associated with return to productivity at 1 year (RTP1). Age was significantly associated with RTP1; however, younger patients had a different association than older patients. After adjustment for individually significant variables, the odds of RTP1 decrease by 14% with every additional week of PTA duration (95% CI 12% to 17%; p<0.0001). The AUC for the Russell intervals was significantly smaller than the Mississippi intervals. CONCLUSIONS: PTA duration is an important predictor of late productivity outcome after TBI. The Mississippi PTA interval classification model is a valid predictor of productivity at 1 year postinjury and provides a more sensitive categorisation of PTA values than the Russell intervals.

Emergence from minimally conscious state: insights from evaluation of posttraumatic confusion.

BACKGROUND: Guidelines for defining the minimally conscious state (MCS) specify behaviors that characterize emergence, including "reliable and consistent" functional communication (accurate yes/no responding). Guidelines were developed by consensus because of lack of empirical data. OBJECTIVE: To evaluate the utility of the operational threshold for emergence from posttraumatic MCS, by determining yes/no accuracy to questions of varied difficulty, including simple orientation questions, using all items from the Yes/No Subscale of the Mississippi Aphasia Screening Test. METHOD: Prospective observational study of a cohort of responsive patients recovering from traumatic brain injury in an acute inpatient brain injury rehabilitation program. RESULTS: Of the 629 observations from 144 participants, name recognition was the easiest yes/no question, with nonconfused individuals responding with 100% accuracy, whereas only 75% to 78% of confused participants on initial evaluation answered this question correctly. Generalized Estimating Equations analysis revealed that confused participants were more likely to respond inaccurately to all yes/no questions. Nonconfused participants had a reduction in odds of inaccuracy ranging from 45.6% to 99.7% (p = 0.001 to 0.02) depending on the type of yes/no question. CONCLUSIONS: Accuracy for simple orientation yes/no questions remains challenging for responsive patients in early recovery from traumatic brain injury. Although name recognition questions are relatively easier than other types of yes/no questions, including situational orientation questions, confused patients still may answer these incorrectly. Results suggest the operational threshold for yes/no response accuracy as a diagnostic criterion for emergence from the minimally conscious state should be revisited, with particular consideration of the type of yes/no questions and the requisite accuracy threshold for responses.

Serial yes/no reliability after traumatic brain injury: implications regarding the operational criteria for emergence from the minimally conscious state.

BACKGROUND: Published guidelines for defining the "minimally conscious state" (MCS) included behaviours that characterise emergence, specifically "reliable and consistent" functional interactive communication (accurate yes/no responding) and functional use of objects. Guidelines were developed by consensus because of the lack of empirical data to guide definitions. Criticism emerged that individuals with severely impaired cognition would have difficulty achieving the requisite threshold of accuracy and consistency proposed to demonstrate emergence from MCS. OBJECTIVE: To determine the utility of the operational threshold for emergence from post-traumatic MCS, by evaluating a measure of yes/no accuracy (Cognitive Test for Delirium, auditory processing subtest (CTD-AP).) METHODS: Prospective, consecutive cohort of responsive patients recovering from traumatic brain injury (TBI), including a subset meeting criteria for MCS at neurorehabilitation admission who improved and were able to undergo the study protocol. Participants were evaluated at least weekly, and given the CTD-AP to assess yes/no responding. RESULTS: Of the 1434 observations from 336 participants, 767 observations yielded inaccurate yes/no responses. 75 participants (22%) never attained consistently accurate yes/no responses at any time during their hospitalisation. Generalised estimating equations analysis revealed that confused participants were more likely to respond inaccurately to yes/no questions. Further, the subset of individuals who were in MCS on rehabilitation admission and improved, were also more likely to respond inaccurately to yes/no questions. CONCLUSIONS: Consistent yes/no accuracy is uncommon among responsive patients in early recovery from TBI. These results suggest that the operational threshold for yes/no response accuracy as a diagnostic criterion for emergence from MCS should be revisited.