Introduction
The Sport Concussion Assessment Tool-5 (SCAT5) was a product of the recent consensus meeting of the Concussion in Sport Group in Berlin, and represents the most recent revision of the 12-year-old SCAT.1 2 The SCAT has proven to be an effective tool in assisting with diagnosing sports-related concussions, although its role in tracking postconcussion recovery and return-to-play decision-making remains unclear.3 The various versions of the SCAT have found use in baseline assessment, as well as a stand-alone test following head injury.3
The primary neurocognitive portion of the SCAT has been the 30 items of the Standardized Assessment of Concussion (SAC),4 which includes measures of orientation, concentration, immediate memory and delayed recall. Deficits in learning and memory have been implicated historically as among the most sensitive components of diagnostic tests for sports-related concussions within 24–48 hours after the injury.5 6 The primary measure of learning and memory on the SAC is a five-item word list over three learning trials. McCrea et al 7 reported overall SAC scores for recently concussed athletes to be significantly lower than the mean score for athletes who underwent baseline testing. Specifically, regarding immediate memory, athletes tested directly following a sports-related concussion demonstrated significantly lower immediate memory subtest scores compared with non-injured athletes during baseline testing. Delayed recall scores remained consistent with the trend observed for immediate memory on the SAC, as non-injured athletes demonstrated significantly higher delayed recall abilities when compared with athletes who recently sustained a concussion.7 McCrea et al 4 7 and Echemendia and Julian8 have shown that baseline performance on the SAC word list typically results in medians of 14 correct out of 15 on total immediate recall and four words correct out of five on delayed recall.
As Echemendia et al 3 noted, a limitation of previous versions of the SCAT (ie, prior to the SCAT5) is the ceiling effect observed in the immediate and delayed recall trials. Assessments with a significant ceiling effect may obscure actual ability in either of two ways. First, noting that an individual scores at the top of a test conveys an interpretation that the individual’s ability is very high. Second, scoring at the ceiling prevents persons of greater ability the opportunity to demonstrate that ability. In the current instance with the SCAT, someone of high ability may score at the ceiling both on baseline and post-trauma, and neither of those scores is a true representation. As described by Echemendia et al,3 the SAC ceiling effect likely has limited the clinical utility of previous versions of the SCAT, as it is not sensitive to subtle verbal learning and memory changes following a concussion. The problematic nature of the ceiling effect is evidenced by the SAC immediate memory subtest mean of 14.51 out of 15, which suggests that perfect scores are common within this population.8 To further evidence the ceiling effect of the five-item word list, Shehata et al 9 reported that all athletes in their study (n=249) were able to recall at least four out of five words during the immediate recall trial (the original SCAT had only one learning trial), with the majority of participants able to recall all five words. During the delayed five-word recall, nearly 37% of athletes were able to recall all five words.9 In order to avoid such a ceiling effect in assessing this critical domain, the SCAT5 authors introduced an optional 10-item word list. The current study is the first to present normative performance of college athletes on the 10-item word list of the SCAT5.