Objective: Sports-related concussion has received increasing attention as a cause of short- and long-term neurologic symptoms among athletes. The King-Devick (K-D) test is based on measurement of the speed of rapid number naming (reading aloud single-digit numbers from 3 test cards), and captures impairment of eye movements, attention, language, and other correlates of suboptimal brain function. We investigated the K-D test as a potential rapid sideline screening for concussion in a cohort of boxers and mixed martial arts fighters.
Methods: The K-D test was administered prefight and postfight. The Military Acute Concussion Evaluation (MACE) was administered as a more comprehensive but longer test for concussion. Differences in postfight K-D scores and changes in scores from prefight to postfight were compared for athletes with head trauma during the fight vs those without.
Results: Postfight K-D scores (n = 39 participants) were significantly higher (worse) for those with head trauma during the match (59.1 ± 7.4 vs 41.0 ± 6.7 seconds, p < 0.0001, Wilcoxon rank sum test). Those with loss of consciousness showed the greatest worsening from prefight to postfight. Worse postfight K-D scores (r(s) = -0.79, p = 0.0001) and greater worsening of scores (r(s) = 0.90, p < 0.0001) correlated well with postfight MACE scores. Worsening of K-D scores by ≥5 seconds was a distinguishing characteristic noted only among participants with head trauma. High levels of test-retest reliability were observed (intraclass correlation coefficient 0.97 [95% confidence interval 0.90-1.0]).
Conclusions: The K-D test is an accurate and reliable method for identifying athletes with head trauma and is a strong candidate rapid sideline screening test for concussion.
Summary Points:
- The K-D test is an accurate and reliable method for identifying athletes with head trauma.
- High degrees of test-retest reliability for the K-D were noted in this study (ICC=0.97).
- In the absence of concussion, athletes demonstrated improvement of K-D scores post-fight.
- Post-fight K-D time scores were worse for participants who had head trauma during their matches.
- Post-fight K-D times scores correlated with the Military Acute Concussion Evaluation (MACE) scores.
- The K-D test captures many aspects of neurological function including eye movements, attention, language.
- The K-D test may help coaches and trainers with game decisions regarding removal of a players who may have been concussed.