A simple vision test performed on the sports sidelines was able to identify nearly 8 out of 10 athletes later found to have suffered a concussion, and when combined with screens for cognition and balance, allowed identification of concussed athletes with 100% accuracy, according to an abstract of a research paper to be presented at the American Academy of Neurology Annual Meeting in Philadelphia in late April 2014. (1)
The study provides more evidence that the King-Devick test, a one-minute test in which athletes are timed reading single-digit numbers on index cards (see photo at right from MomsTEAM's PBS documentary, "The Smartest Team") , can be used in addition to other tests to increase the accuracy in diagnosing concussion (as was done by the Newcastle, OK high school team featured in The Smartest Team).
Researchers, led by Laura Balcer, MD, MSCE, of New York University (NYU) Langone Medical Center in New York, asked 217 members of the University of Florida men's football, women's soccer and women's lacrosse teams to take the King-Devick test and other concussion tests, including components of SCAT3 , a tool for evaluating injured athletes, at the beginning of the season for baseline scores.
A total of 30 of the athletes had a first concussion during the season and were tested again at the time of the injury or when it was reported the next day (delayed onset of concussion symptoms, it should be noted, is not uncommon, especially in younger athletes). Of the athletes diagnosed with concussion, 79% took longer after injury to complete the King-Devick test (which usually takes less than one minute) than they did their pre-season baselines. Combining the results with those from a widely used test of cognition called the Standardized Assessment of Concussion  and a balance test (the Balance Error Scoring System ), researchers were able to identify100 percent of the concussed athletes. Athletes with worse/slower scores on the King-Devick test also were more likely to have concussion symptoms  on the 22-item Post-Concussion Symptom Scale (PCSS), especially sensitivity to light and noise.
An earlier 2011 study using King-Devick among a group of mixed-martial arts athletes (2) found that, while the times of athletes who had not suffered head trauma were actually faster, due to a mild learning effect from test to test, the times for those found on subsequent examination to have suffered head trauma were at least 5 seconds slower. At that time researchers believed that the 5-second "threshold may be a useful cutoff for exploration in future studies as a criterion for having an athlete stop play pending medical evaluation for concussion."
While Balcer and her colleagues found that average for those later diagnosed with concussion in the current study "happened to be around 5 seconds," their thinking now is that any worsening of score from baseline should raise suspicion of concussion. Simply put, she said, they erred on the side of caution because they didn't "want to miss anyone."
The K-D measures the time it takes for an athlete to read a series of single digit numbers displayed on index-sized cards. Previous studies of boxers and mixed martial arts (MMA) fighters  (2), collegiate athletes  in contact sports (3), in a New Zealand rugby league  (4,5), and in a small group of professional hockey players (6), found that an increase (worsening) in the time needed to complete the one-minute K-D was predictive of concussion. While K-D detects fast eye (i.e. saccadic) movements, it also captures language and concentration, all of which have been shown to be impaired as a result of concussion.
Because no single test currently exists which is capable of screening athletes on the sports sideline for all the different ways concussion can present, some leading concussion experts (13) have called for the use of more than one sideline assessment tool, including K-D (although there are others who were, at least of March 2013 (14), saying that "no conclusion can be drawn at this point regarding the eventual usefulness of the [K-D Test]."
That the NYU researchers found that K-D, when combined with the results from the SAC and BESS as part of a battery of rapid concussion screening tools, allowed sideline personnel to identify virtually all athletes suspected of concussion, would appear to add further weight to the argument in favor of its use on the sports sideline.
"The visual pathways are commonly affected in concussion," said Balcer. "Adding a vision-based test to evaluate athletes on the sidelines may allow us to better detect more athletes with concussion more quickly. This is particularly important, since not all athletes reliably report their symptoms of concussion, including any vision problems."
The resistance  or complete unwillingness of many athletes - even those with detailed understanding of the signs and symptoms  of and risks associated with concussion (7,8) - to honestly self-report their symptoms to sideline personnel (8,9,10) is well-documented. Previous studies have also found that even trained sideline personnel have difficulty spotting the often, sometimes even undetectable, signs of concussion (10,11),
To Balcer's point, the New Zealand rugby studies  (4,5) found that the K-D test was able to detect unrecognized concussions, making it especially valuable as a sideline, or even post-game, concussion screening tool, not just facilitating removal from play of athletes and referral for a more complete assessment away from the sport sideline of athletes who, if allowed to continue play, run the risk of further injury to their brain, and, studies show, are likely to lengthen and complicate recovery, and, worse, increase the chance of permanent brain injury or, in rare cases, death from a form of diffuse cerebral swelling dubbed Second Impact Syndrome , but concussed athletes who might otherwise return to practice, risking further injury.
"It is very exciting to potentially have an objective, rapid sideline screening tool for diagnosing concussion that is quick, simple and easy to administer. Timely early detection of concussion is important in properly treating concussion," said the senior author of the earlier professional hockey study, Christina Master, MD.
"This test has the potential to be a very useful sideline test for athletes and we are looking at its utility in the pediatric and adolescent population where it may be very helpful because there are often no medical personnel on the sidelines of youth competitions."
Indeed, the test has shown such promise for sideline assessment of concussion that consumer advocate Ralph Nader has called for its mandatory use at all levels of sports, from the pros down to youth leagues. (12)
1. More Evidence That Vision Test on Sidelines May Help Diagnose Concussion. American Academy of Neurology via Newswise. February 26, 2014. http://www.newswise.com/articles/view/613709/?sc=sphr&xy=10013227 
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8. Anderson B, Pomerantz W, Mann J, Gittelman M. "I Can't Miss the Big Game": High School (HS) Football Players' Knowledge and Attitudes about Concussions. Paper presented at the Annual meeting of the Pediatric Academic Societies, Washington, D.C. May 6, 2013.
9. "Concussion Confidential" ESPN The Magazine (http://sports.espn.go.com/espn/news/story?id=5925876 )(accessed December 21, 2010).
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11. Echlin PS, Skopelja EN, Worsley R, et. al. A prospective study of physician-observed concussion during a varsity university ice hockey season: incidence and neuropsychological changes. Neurosurg Focus 2012;33(6):E2
12. "Ralph Nader Calls For Mandatory Implementation of King-Devick Concussion Test in High School and Youth Sports" (ttp://leagueoffans.org/2011/08/25/ralph-nader-calls-for-mandatory-implementation-of-king-devick-concussion-test-in-high-school-and-youth-sports/) (accessed August 25, 2011)
13. Cantu R and Hyman M. Concussions and Our Kids (Houghton Mifflin Harcourt 2012), p. 63.
14. McCrea M, Iverson G, Echemendia et al. Day of injury assessment of sport-related concussion. Br J Sports Med 2013;47:272-284.