DETECTION OF COGNITIVE CHANGE: EXAMINATION OF APPROACHES FOR IMPROVING THE ACCURACY OF IMPACT

Concussion is an increasingly recognized public health concern. Proper assessment and management of concussion are critical factors in mitigating adverse effects associated with this injury. Neuropsychological assessment has demonstrated utility in identifying cognitive symptoms related to concussion and monitoring their resolution. Early methods involved administering paper and pencil tests to appraise cognitive domains thought to be most affected by concussion. As interest in concussion and methods of assessment evolved, baseline testing became an integral component of assessment in sport-related concussion (SRC). Baseline testing consists of administering a healthy, or non-injured, individual a battery of cognitive tests that subsequently serve as a reference point to evaluate the individual’s performance on the same tests following a suspected injury or change in cognitive status. Recent advances, spurred by an interest in increasing access to baseline testing, contributed to the adoption of computerized neurocognitive tests (CNTs). CNTs allow for baseline testing of groups of individuals, in one setting, and in a short amount of time. Immediate Post Concussion and Cognitive Testing (ImPACT) has emerged as the most commonly used CNT in the assessment and management of SRC. This body of research aimed to explore ImPACT’s reliability and validity to appraise its efficacy in accurately detecting cognitive change associated with concussion and explore potential improvements. The first chapter is devoted to examining ImPACT’s test-retest reliability, which refers to the expected consistency in results over time in healthy individuals. This study examines ImPACT score reports for 107 healthy individuals that included testing at two time points. Results reveal less than adequate test-retest reliability attributable to, at least in part, a restricted range of possible scores, or the presence of a ceiling effect, on numerous subscales. Additional discussion includes corrective measures, such as proactively identifying individuals producing maximum scores on baseline testing, extending the length of subscales, and incorporating adaptive testing. The second chapter evaluates ImPACT’s validity, and specifically, its classification accuracy in differentiating between individuals with and without concussion. This study incorporates a novel approach through its use of standardized regression based (SRB) reliable change index (RCI) scores to measure post-injury testing deviations from baseline scores. The SRB methodology, coupled with discriminant function analyses (DFAs), is compared to current interpretive procedures. The study includes 129 individuals without concussion whose SRB RCI scores are compared to 81 individuals with concussion. Results of analyses suggest that the current interpretive procedure performs at a chance level in accurately identifying individuals with concussion; conversely, the SRB method and DFA approach yield positive predictive values exceeding 80%, however sensitivities below 50%. Additionally, the Post Concussion Symptom Scale (PCSS), a self-report measure of symptoms, is largely equivalent to ImPACT’s cognitive measures in classification accuracy. Collectively, these results raise considerable concern regarding ImPACT’s efficacy as a measure to aid in the assessment and management of concussion.