The alternate forms of the ImPACT neurocognitive test aren't necessarily reliable when evaluating whether someone has sustained a concussion, according to a study published online earlier this month in the journal The Clinical Neuropsychologist.
Many youth-athletes across the nation are administered the ImPACT test battery before they ever step onto a playing field in order to test their "baseline" brain activity. When suspected of a concussion, the youths go through the ImPACT battery once more to detect any significant changes in their brain activity.
ImPACT has five alternate forms that are "designed to minimize practice effects associated with repeat testing while simultaneously maintain[ing] test sensitivity," according to the study. In other words: The alternate forms aim to prevent test-takers from gaming the system by learning and memorizing the answers.
For this study, the lead author, University of Texas-Arlington professor Jacob E. Resch, sought to evaluate the equivalence of the ImPACT alternate forms to help explain reported test-retest variability. (Resch published another study earlier this year in the Journal of Athletic Training which found ImPACT tests to misidentify healthy participants in certain circumstances up to 46 percent of the time.)
The researchers administered three forms of ImPACT to 108 fully healthy college-aged participants, 33 males and 75 females, divided into six groups. Participants were excluded if they had a history of concussion within six months of the study. Each of the six groups was administered Form 1 on the first day of the study, but each group received a pairing of different forms (on days 45 and 50) from there.
Theoretically, if the alternate forms were equivalent, each group would score the same across different areas, including verbal memory, reaction time, and visual memory.
Instead, the researchers determined that nearly 1 in 5 comparisons (19 percent) were nonequivalent. Some of the study subjects performed markedly better on some of the latter tests of verbal and visual memory, motor speed, and reaction time, while others performed significantly worse.
The weakest reliability coefficients were ImPACT's verbal and visual memory composite scorers, the study found. The authors hypothesized that "word and design lists that vary in difficulty/complexity" could be to blame for the divergence of scores.
"Our results provide information for clinicians who must determine if changes between baseline and post-injury assessments are the result of the sport concussion or psychometric characteristics of the ImPACT's alternate forms," the study authors wrote.
Resch emphasized to TheVerge.com that despite the findings of this study, ImPACT tests can still be a valuable concussion-management tool.
"We use the ImPACT," he said. "We absolutely do. And as research shows, it's one of the best tests on the market."
His study simply aims to shed some light on the discrepancies between certain baseline and post-concussion scores, which could help doctors make more informed decisions when evaluating a youth athlete for a concussion.
Want all the latest K-12 sports news? Follow @SchooledinSport on Twitter.