Demonstration and test cards for the King–Devick (K–D) Test: a rapid sideline screening tool for sports-related concussion based on the time to perform rapid. Background The King-Devick (KD) test is an objective clinical test of eye movements that has been used to screen for concussion. A rapid, cost-effective, and reliable tool that facilitates diagnosis of concussion is needed. The King-Devick (K-D) test is a vision-based tool of rapid number.
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Sports-related concussion has received increasing attention as a result of neurologic sequelae seen among athletes, highlighting the need for a validated, rapid screening tool. The King—Devick K—D test requires vision, eye movements, language function and attention in order to perform and has been proposed as a promising tool for assessment of concussion.
We investigated the K—D test as a sideline screening tool in a collegiate cohort to determine the effect of concussion. K—D testing was administered immediately on the sidelines for football players with suspected head injury during regular games and changes compared to baseline were determined.
Concussipn testing demonstrated improvement of scores and was consistent with known learning effects The data show worsening of Yest test scores following concussion further supporting utility of the K—D test as an objective, reliable and effective sideline visual screening tool to help identify athletes with concussion.
It is teest that sports-related concussion afflicts 3. The function of eye movements may become impaired following brain trauma.
The King—Devick K—D test is a 2-min, sideline assessment of rapid number naming which requires the athletes to quickly read a series of numbers on three test cards Fig. The K—D test requires eye movements, language function and attention in order to perform functions which have been shown to reflect suboptimal brain function in concussion, 23—31 Parkinson’s, 32 multiple sclerosis, 33 extreme sleep deprivation, 34 and hypoxia.
ARVO E-abstract and hockey. The addition of this type of vision based test has also been shown to enhance the detection of athletes with concussion. To perform the K—D test, participants are concuseion to read the numbers from left to right as quickly as they can without making any errors.
The tester should start the stopwatch when the subject reads the first number and stop the watch when the last umber has eevick read. Time required to complete each card are recorded and in seconds using a stopwatch and the K—D time score is based on the cumulative time taken to read all 3 test cards. The number of errors made in reading the etst cards is also recorded; misspeaks on numbers are recorded as errors if the subject does not immediately correct the mistake before continuing on to the next number.
The purpose of this investigation was to further determine the concusxion of concussion concussin K—D scores compared to pre-season baseline in collegiate level football athletes. Additionally, the effect of physical exercise on K—D scores in the absence of concussion was studied.
For this study of collegiate athletes, athletes were enrolled at the time of pre-season physical examinations for the — season. Athletes were players from the football team and the men’s and women’s basketball teams.
Participants underwent pre-season baseline testing with the K—D test. During the playing season, the K—D test and a modified version of the Sport Concussion Assessment Tool 2 SCAT2 were both utilized in the sideline assessment of athletes suspected of head trauma. The K—D test includes one demonstration card and three test cards that vary in format Fig.
Standardized instructions are used and participants are asked to read the numbers from left to right as quickly as they can without making any errors. Time is kept for each test card using a stopwatch and the K—D summary score for the entire test is based on the cumulative time taken to read all 3 test cards.
The number of errors made in reading the test cards is also recorded. A baseline score is established by testing a subject twice. The best time fastest of the two trials without errors becomes the established baseline K—D test time. The test is administered once using the same instructions and the time and errors are recorded and then compared to the subject’s baseline.
This version included the following standardized SCAT2 subtests: SCAT2 results were recorded as a pass or fail based on the presence of any SCAT2 defects in which an athlete displayed any signs of symptoms of concussion i.
Baseline K—D times for all athletes were established during pre-season physical exams with multiple individuals being testing simultaneously in a noisy training room environment. Subjects were given standardized instructions for the K—D test.
Judgments with conchssion to the occurrence of concussion were made as per standard practice by the team physicians and athletic trainers on the sidelines. Post-season testing was also performed on a convenience sample of non-concussed football devikc to determine how K—D performance changes over the course of a season in the absence of concussion.
Additionally, basketball players were tested immediately following an intense 2. Changes in K—D time scores from pre- to post-season were calculated and compared using the Wilcoxon signed-rank test. Similarly, differences in sideline K—D scores were calculated and compared to pre-season baseline scores in athletes with concussion.
Wilcoxon signed-rank test was also used to compare K—D time scores pre- and post-exercise for the basketball teams. Test-retest reliability was estimated using the intraclass correlation coefficient ICC to examine agreement between pre- and post-season scores among athletes without concussion.
Characteristics and K—D testing data for the study cohort are shown in Table 1.
The King–Devick test for sideline concussion screening in collegiate football
Lower improved K—D time scores were observed for the second K—D trial compared to tesy first during baseline testing of football players median K—D testing data for concussed and non-concussed football players are shown in Table 2.
All concussed athletes, with the exception of two, failed sideline SCAT2 testing. These two athletes showed worsening on their sideline K—D test 1. All athletes who sustained a concussion during the playing season exhibited defects in their sideline K—D tests. There were minimal errors with one concussed athlete making 1 error on sideline testing. This athlete did not substantially worsen from baseline with respect to their K—D time score Post-workout data were obtained during a practice in the middle of the season for the men’s and women’s basketball teams immediately following a 2.
No concussions were sustained in these athletes. K—D scores post-workout showed faster improved K—D scores There was no worsening of K—D scores following physical fatigue in tezt absence of concussion Fig. Box plots show the median K—D scores of baseline compared to sideline, post-workout and post-season testing.
The line within the box defines the median value. The range of the box corresponds to the interquartile range between the 25th and the 75th percentile.
Whiskers extending from the box plot represent the range of observations excluding outliers and the small circles beyond the whiskers represent symbolize outliers. This study provides additional evidence for the use of the K—D test as an effective, objective sideline assessment tool for concussion. Concussed athletes performed slower on their sideline K—D test compared to baseline with an average slowing from baseline of 4. This finding was similar to previous studies that have also shown worsening of score with concussion.
The difference between average changes in times when compared to previous studies 23—30 may be reflective of the population tested, prior history of concussion and the conditions the athletes were tested. Prior studies have included boxers and MMA fighters 23 who were observed to have sustained obvious head trauma. The concussive injuries identified in the current study may have been less severe as overt head trauma was not always witnessed.
In a previous study 24 both male and female athletes with concussion were included whereas the current study only included male football players. This may also have played a role in the disparity between average worsening among studies as previous work has shown that gender may be a risk factor for injury and may influence injury severity. Detecting concussion on the sidelines, and removing an athlete from play, can assist to minimize the deleterious outcomes of concussion.
Rapid screening tools that can be practically implemented into the sideline evaluation of athletes are vital to the detection of concussive injuries. The K—D test is portable and easy to implement on the sidelines. The K—D test is simply based on time to complete a rapid number naming task. It does not require a medical professional to administer 28 and is therefore a realistic tool for high schools and youth sports organizations, the majority of which do not have access to medical personnel.
The K—D test requires visual processes, eye movements saccades, convergence and accommodationattention and language function. These involve integration of functions of the brainstem, cerebellum, and cerebral cortex and have shown to correlate with suboptimal brain function.
However, the SCAT2 does not objectively assess vision or eye movement function. Some have questioned the utility and sensitivity of the SCAT2 in detecting 39 as well as its overall reliability. Concussion signs and symptoms may develop and evolve over time, particularly within the first hours following injury. Recent work investigating the sensitivity of sideline concussion tests used in collegiate level athletics has shown that key components of the SCAT2, the SAC and BESS, failed to capture all concussions.
Since the completion of data collection for this study, the SCAT2 has been updated to the SCAT3 2 for sports participants over the age of 12 years and the Child-SCAT3 with modified questions asked for athletes between the ages of 5 and 12 years old.
Future studies are recommended to investigate the additive effect of sideline K—D test and the new SCAT3 for detection of concussion.
This study was similar to previous investigations showing that in the absence of concussion, the K—D test has a learning effect associated with repeated testing. Previous investigations of athletes without concussion showed an improvement on average of 2. The athletes in this study improved by their baseline trials by an average of 2.
Pre-season and post-season testing showed an improvement of 1. This is similar to prior fatigue studies performed in collegiate basketball athletes Errors committed in this study were minimal with one concussed athlete making a single error. This is similar to previous studies in which four concussed athletes made one to four errors in addition to worse sideline K—D test times; 24 however, in this study the error was not associated with worsening of time score. Formal eye movements studies 19,20 suggest that these errors likely indicate eye movement inaccuracy as a result of TBI occurring.
However, this may also be a reflection of impaired visual processing, concentration, attention or language function. Prior eye movement recorded studies of the K—D test for early detection of hypoxia related cognitive impairment have also shown that errors correlated with hypoxic impairment.
It is important to note that no errors were made by non-concussed athletes in this study and in prior studies suggesting that worsening of time from baseline or any errors committed deserves further concussion assessment.
The King-Devick test as a determinant of head trauma and concussion in boxers and MMA fighters
Follow-up K—D testing of concussed athletes was not performed on this cohort. Other studies 24,25 have shown improvement and return to baseline. A study reporting on collegiate athletes showed return to baseline within one week following the concussive event, 24 whereas an investigation of rugby athletes 25 showed more variation ranging from one week to beyond 21 days in some athletes in the amount of time elapsed before concussed athletes returned to their established baseline.
Interestingly, the time frame to return to baseline appeared to correspond with the severity of injury with the more severe, witnessed concussions taking longer to return to baseline 14 days to more than 21 days compared to incidentally found concussions. It is recommended that future studies should continue to investigate the utility of the K—D test in concussion management and recovery to determine if there is correlation with clinical improvement.
Concussion may result in a variety of symptoms and may go both unreported by athletes and undetected by trained observers. The results of this study further validate the K—D test as an accurate, reliable and rapid sideline tool that provides supportive evidence of a concussive event to help objectively identify athletes with concussion and assist with removing from play decisions.
It is recommended that future studies should continue to investigate the reliability of the K—D test in detecting concussion across a range of age groups from youth to professional levels, and throughout a variety of contact sports. Galetta has served as a consultant for Biogen Idec and Vaccinex. The work performed in this study was not funded by any of the above sources and the remaining authors have no disclosures.
The authors are grateful to the Wheaton College Sports Medicine staff for their support in study organization, implementation and testing of athletes.