Research Reports - Using post-traumatic amnesia to predict outcome after traumatic brain injury
J Neurotrauma. 2015 Oct 13. [Epub ahead of print]
Using Post-Traumatic Amnesia To Predict Outcome after Traumatic Brain Injury.
Ponsford JL(1), Spitz G(1), McKenzie D(2).
(1)1 School of Psychological Sciences, Monash University , and Monash-Epworth
Rehabilitation Research Centre, Epworth Hospital, Melbourne, Australia . (2)2
Research Development & Governance, Epworth Healthcare, and School of Public
Health and Preventive Medicine, Monash University , Melbourne, Australia .
Duration of post-traumatic amnesia (PTA) has emerged as a strong measure of
injury severity after traumatic brain injury (TBI). Despite the growing
international adoption of this measure, there remains a lack of consistency in
the way in which PTA duration is used to classify severity of injury. This study
aimed to establish the classification of PTA that would best predict functional
or productivity outcomes. We conducted a cohort study of 1041 persons recruited
from inpatient admissions to a TBI rehabilitation center between 1985 and 2013.
Participants had a primary diagnosis of TBI, emerged from PTA before discharge
from inpatient hospital, and engaged in productive activities before injury.
Eight models that classify duration of PTA were evaluated-six that were based on
the literature and two that were statistically driven. Models were assessed using
area under the receiver operating characteristic curve (AUC) as well as
model-based Akaike Information Criterion (AIC) and Bayesian Information Criterion
(BIC) statistics. All categorization models showed longer PTA to be associated
with a greater likelihood of being nonproductive at 1 year after TBI.
Classification systems with a greater number of categories performed better than
two-category systems. The dimensional (continuous) form of PTA resulted in the
greatest AUC, and lowest AIC as well as BIC, of the classification systems
examined. This finding indicates that the greatest accuracy in prognosis is
likely to be achieved using PTA as a continuous variable. This enables the
probability of productive outcomes to be estimated with far greater precision
than that possible using a classification system. Categorizing PTA to classify
severity of injury may be reducing the precision with which clinicians can plan
the treatment of patients after TBI.