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Objective: Mild traumatic brain injury (mTBI) engenders both physical (e.g. headache, vision, vestibular, sleep) and mental (e.g. cognitive, behavioural) symptoms. The ability of computerized neurocognitive assessment tools (NCATs) to identify sequelae specific to mTBI is essential for their use with populations exposed to higher rates of mTBI, e.g. military service members (SMs). Comparison to controls is the current standard for evaluating the validity of NCATs. We hypothesize that using symptom reports may be a methodological improvement for evaluation of NCATs.
Participants and Methods: SMs (272 controls, 232 acute mTBI) took two NCATs (ANAM4, CNS-VS, CogState, ImPACT), a traditional neuropsychological battery, and three validated symptom inventories (e.g. PHQ9, PCL, NSI). Multivariate analyses isolated the unique variance in NCAT scores attributable to symptom factors (identified by factor analysis) within the mTBI cohort, controlling for IQ.
Results: Self-reported symptoms loaded onto five main factors: somatic complaints, depression, Post-traumatic stress symptoms, cognitive issues, and sleep/fatigue. Aggregated, factor scores explained a significant proportion of variance in NCAT performance (R2 change = .150 to .307, p <0.001), notably on the composite score, reaction-time and processing speed tests on ANAM4, verbal memory domain on CNS-VS, the composite score, reaction time and visual processing tests on CogState, and visual memory and motor speed indices on ImPACT. Predictive contributions varied, with somatic and cognitive issues explaining the most variance in tests of reaction time, visual processing and motor speed, and the affective symptoms together explaining the most variance in tests of learning and memory.
Conclusions: The use of symptom ratings may allow for more granular understanding of the role of NCATs in identifying sequelae after mTBI. This methodology appears to show more promise than categorical injury classifications and may be a more clinically relevant means of measuring the utility of NCATs.