LOS ANGELES—The King–Devick test may be a more objective and accurate method for the sideline evaluation of sports-related concussion than the Standardized Concussion Assessment Tool 3 (SCAT3), which is the current standard, according to research reported at the 56th Annual Scientific Meeting of the American Headache Society. Several studies of the King–Devick test are “showing that it has a number of advantages over the SCAT3” and soon may become the new standard, said Bert B. Vargas, MD, Assistant Professor of Neurology at Mayo Clinic in Phoenix, Arizona.
In a recent study of collegiate football players, the King–Devick test successfully identified approximately 80% of participants with concussion. In contrast, the Standardized Assessment of Concussion (SAC), a component of SCAT3, identified slightly more than half of participants with concussion. Administering the King–Devick and SAC tests identified approximately 90% of concussions, and administering the SCAT3 and the King–Devick tests identified every athlete with concussion, said Dr. Vargas, citing a study recently published in Neurology Clinical Practice. No single test will be the “one and only go-to tool,” he added. Rather, a combination of measures may be the best way to identify players who have had concussion.
Bert B. Vargas, MD
SCAT3 and Its Weaknesses
SCAT3 includes the Graded Symptom Checklist, a series of 22 symptoms that a player grades on a scale of 0 to 6, the SAC, which screens for cognitive deficits, and the Modified Balance Error Scoring System (BESS), which requires players to achieve and maintain a series of three stances to assess their balance.
Scores for the symptoms on the checklist can be added to give the neurologist an idea of how the player is feeling at that moment. The checklist’s sensitivity has been shown to have a significant degree of variability, “and I would argue that it is incredibly subjective,” said Dr. Vargas. Because athletes often minimize or fail to report their symptoms, the Graded Symptom Checklist “can be unreliable as a sole determinant of whether someone has had a concussion,” said Dr. Vargas. The most accurate way to obtain an assessment of a player’s symptoms on the checklist may be for a physician to review each of the symptoms with the player and discuss how the latter graded each one.
The SAC evaluates orientation, immediate memory, concentration, and delayed recall, but it has several weaknesses. First, the SAC takes time to administer. “It is typically expected that decisions at the professional and collegiate levels be made quickly but accurately, which poses some unique challenges,” said Dr. Vargas.
Second, the immediate-memory section of the SAC tests whether the player can repeat a list of five words that he or she has heard. If the player has taken the test before, the physician may choose from other banks of words. But athletes who have taken the test several times frequently begin to memorize the words. Some players begin reciting the words before the question is asked, “leaving one to question the validity and reliability of the data obtained from those athletes,” said Dr. Vargas.
Finally, among providers who care for athletes, an acceptable deviation from baseline usually requires a degree of subjective interpretation of the results without any formal quantitative guidelines regarding how much change is acceptable. Decisions are easier to make if the provider administering the test knows the athlete well. SCAT3 results from unfamiliar athletes and those without a baseline can sometimes be difficult to interpret reliably. The Modified BESS has a wide sensitivity range, and “its best reported sensitivity is poor,” said Dr. Vargas. The test is “incredibly subjective” and often administered inappropriately, he added. When he and his colleagues administered the Modified BESS to collegiate football players, the majority of the participants could not execute the single-leg stance without receiving the worst possible score. “These are elite athletes preseason before any injuries,” Dr. Vargas emphasized. “If athletes are being given maximal error scores at baseline, how is it possible to assess any change after injury?”
King–Devick Test Has High Inter-Rater Reliability
The King–Devick test includes a series of cards printed with numbers that the player must read from left to right and from top to bottom. On the first card, arrows indicate the direction in which to read the numbers, but each successive card contains fewer arrows. The measure takes less than two minutes to administer and sometimes may require less than one minute to administer.
The King–Devick test is practical for use anywhere and captures several abnormalities for various domains, said Dr. Vargas. The test’s inter-rater reliability is high because the only requirements are starting a stopwatch when the player starts reading the card and stopping the stopwatch when he or she stops reading. Furthermore, the tool’s test-to-test reliability is high.