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ImPACT Concussion Tests Found to Be Unreliable at Times

The neuropsychological concussion test battery known as ImPACT was found to misidentify healthy participants in certain circumstances up to 46 percent of the time, according to a study published this week in the Journal of Athletic Training.

This variance suggests that the tests should only be used as one component of a multi-faceted approach to determining when a student-athlete is ready to return after sustaining a concussion, the authors conclude.

A team of researchers from the United States and Ireland sought to determine the reliability of computerized neuropsychological testing by running two separate sets of students through the ImPACT test battery in different time intervals. One group consisted of students from an Irish university (46 in total), while the other group was comprised of students from a U.S. university (45). All of the students in the study were between the ages of 19 and 24, hadn't sustained a concussion in the six months before or during the study, and were considered nonathletes.

After completing a baseline test at the beginning of the study, the first group of students (from the Irish university) redid the full battery of testing one and two weeks after the initial baseline. The second group of students (from the U.S. university) completed a baseline, then retook the test 45 days and again 50 days after the initial baseline.

In the first group, 17 of the 46 participants (37 percent) were classified as "impaired" in at least one aspect of the test upon retaking it a week after the original baseline, despite being completely concussion-free. Twenty-one of the 46 students in the first group (46 percent) were classified as "impaired" when retaking the test two weeks after baseline. In the second group, 10 of the 45 participants (22 percent) had scores which deviated from their baseline when taking the test 45 days later, and 13 (28.9 percent) deviated on the test taken 50 days after baseline.

While a majority of the test-retest subjects studied experienced no change from baseline to a later test, the variation among scores in healthy test subjects raised concerns among the researchers.

"This research confirms previous findings about ImPACT, and that is especially noteworthy in light of a recent study that found that athletic trainers who use computerized neurocognitive testing choose ImPACT," said lead author Jacob Resch, the director of the UT Arlington Brain Injury Laboratory, in a statement. "We hope this study re-emphasizes the importance of using multiple measures such as balance and a thorough clinical examination to assess concussed athletes."

As noted by ESPN's Outside the Lines in the summer of 2012, previous research has also suggested ImPACT tests may return a false positive rate between 30 percent and 40 percent. Considering that nearly every state now has a law prohibiting concussed student-athletes from returning to play until obtaining medical clearance, these false positives could be unnecessarily delay their return to school- or athletic-based activities.

The lack of conclusive research around neuropsychological testing caused the authors of the latest consensus statement on concussions in sport to stop short of recommending its widespread use. The statement said such testing "contributes significant information in concussion evaluation," but noted that it shouldn't be the only determining factor as to whether or not a concussed student-athlete is ready to return to play.

Likewise, the American Academy of Neurology earlier this year also acknowledged the role of neuropsychological testing, saying it is "likely useful in identifying the presence of concussion," but also noted the lack of conclusive evidence regarding its reliability.

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