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King-Devick Test Promises More Rapid, Reliable Sideline Screening for Concussions

May provide bright line for all-important return to play decision, predict post-concussion syndrome

A test long used to test vision and reading has the potential to provide rapid and accurate sideline screening of concussion on the sports sideline, says a groundbreaking study reported in the journal Neurology.1

Researchers at the University of Pennsylvania tested boxers and mixed martial arts (MMA) fighters before and after sparring sessions or bouts using the King-Devick (K-D) test, a simple, two-minute test in which the athletes were shown a set of three index cards with a series of numbers scattered across eight lines and asked to read the numbers as quickly as possible without any errors from left to right.  The K-D time score is the sum of the 3 test card time scores. 

On re-testing, researchers found that, while the times of athletes who had not suffered head trauma were actually faster, the times for those found on subsequent examination to have suffered head trauma were at least 5 seconds slower.

The slower times led researchers to believe 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."Lacrosse player shooting on goal

May become standard sideline test

"The results of this study demonstrate that the K-D test is an accurate and reliable method for identifying athletes with head trauma, and is a strong candidate for a rapid sideline  screening test for concussion, [with] particular relevance to contact sports including football, soccer, hockey, MMA and boxing," wrote co-author, Dr. Laura J. Balcer of the Department of Neurology, Opthalmology, and Epidemiology at the University of Pennsylvania School of Medicine.

"Our data indicate that head trauma events can be effectively identified by K-D test time scores, and that analyses of this new measure in future studies can establish its role as a rapid sideline screening test for concussion,"  she writes. 

The K-D test, originally developed in the 1980's by optometrists Al King and Steve Devick at the Illinois College of Optometry, provides objective measures of many aspects of brain function, including subcortical (subconscious) pathways that extend beyond eye movements.  As result, it  "may help coaches and trainers with game decisions regarding removal of a player who may have been concussed," the study says.

Easy to use

Because the test is simple, quick and easy to administer, not just by athletic trainers or health care professionals but parents and coaches, it may have particular value in sideline screening for concussion at the youth level, where immediate evaluation for head trauma by a trained professional is often not possible.

Once an athlete's baseline score has been established, re-testing can then be performed right on the sports sideline, as the "test stands up in an active setting", Dr. Balcer told MomsTeam.  Because the test takes less than two minutes to perform, it could be performed during a single football or basketball time out.  Any worsening of scores could then investigated further using other clinical tests for concussion.

While studies have not yet been performed using the K-D test in screening athletes at the youth and high school level, the long use of the test in diagnosing reading problems in children  "gives me reason to be very optimistic that the test could help parents and coaches to determine whether an athlete who has been hit may have suffered a concussion," Dr. Balcer told MomsTeam. She emphasized, however, that King-Devick was only meant for use as an initial screen to identify athletes who should not be allowed to return to the game or practice and who should be referred for further, more comprehensive evaluation by a trained professional (e.g. assessment of balance, neurocognitive function, and scores on the Post-Concussion Symptom Scale).

Concussion recognition and management is difficult

As the study notes, there are four main reasons why recognition and management of concussions in athletes represents such a challenge:

  1. Wide variety of often-subtle symptoms.  While some athletes with mild concussion experience such classic symptoms as loss of consciousness, confusion, and memory loss, the symptoms are typically quite subtle and "may go unnoticed or overlooked by the athlete, team medical staff, or coaches."  In the absence of an athletic trainer or physician, the job of identifying the often subtle signs of concussion often falls to parent and volunteer coaches without adequate training.  Using the K-D test could allow such sideline personnel to quickly and accurately determine which athletes need to be held out of play after suffering a suspected head injury.
  2. Evidence-based management guidelines lacking.   Most concussion and return-to-play guidelines issued before 2000 used numeric grading scales and relied on the presence/absence of loss of consciousness (LOC) and post-traumatic amnesia (PTA) to determine the severity of a concussion and return to play (RTP). None gained universal acceptance or were consistently followed by sports medicine professionals, many of whom ended up not using any grading scale for evaluation or RTP purposes.  Concussion management guidelines in the early 2000s moved away from reliance on LOC and PTA as sole predictors of injury severity. They focused instead on the number and duration of all post-concussion signs and symptoms.  In recent years, experts acknowledged that the current state of knowledge about concussions did not allow severity of injury to be determined at the time of injury but only after all signs and symptoms had cleared, and recommended that concussion management be performed on an individualized, case-by-case, basis taking into account a variety of factors.  Use of the King-Devick test could provide an objective, evidence-based measure of impaired brain function;
  3. Traditional neurologic and radiologic testing not useful in identifying concussion effects. Tests such as CT scans, MRI scans, and EEG, although helpful in identifying more serious consequences of head trauma (e.g. skull fracture, hematoma, contusion, seizure) are not useful in identifying many of the effects of concussion, and are usually normal, even in athletes sustaining a severe concussion (in fact, a normal CT or MRI is considered one of the common features of a concussion); and
  4. Athletes minimize or deny symptoms.  Athletes often do not understand the potential consequences of concussion, and often minimize or deny symptoms so that they can return to play, with under-reporting a chronic and ongoing concern.  As an objective measure of impaired brain function, the King-Devick test could help identify athletes with suspected concussion, even if, in their desire to continue playing, they deny any impairment.

Predicting post-concussion syndrome

Studies show that saccadic movements - the quick eye movements used in reading - are frequently abnormal following concussion and may predict whether an athlete will suffer from postconcussion syndrome (e.g. symptoms which persist over a long period of time, instead of clearing within the first 7 to 10 days, as in the vast majority of cases)(over 90% in one recent study).

Impaired eye movement function has also been shown to correlate well with the severity of postconcussion symptoms and with limitations of activities of daily living.  "Collectively, data on eye movement testing demonstrates a high degree of sensitivity and predictive value as an outcome measure for concussion," observes the study.

In the K-D test, a test-taker reads from left to right eight rows of unevenly spaced, single digit numbers on three test cards as quickly and accurately as possible.  It not only measures the speed of rapid number naming, thus capturing impairment of saccadic eye movements, but the test-taker's balance, attention, language and visual recognition skills.  

Further study underway

While the study focused on boxers and MMA fighters, where head trauma was observable and easy to spot, researchers are optimistic that the K-D test will prove valuable in other sports, such as football - where closed head injury and concussion may occur in the context of plays involving many individuals, and head trauma may not be as readily detected - in determining if a meaningful head blow has taken place that warrants removing a player from the game or practice for further evaluation. 

To determine whether the test works as well in such sports settings, a study is currently being conducted of members of the University of Pennsylvania football team, men's and women's soccer teams, and men's and women's basketball teams, with the results expected in a matter of months.  Researchers hope the new study  "will establish large-scale test norms and expected ranges of pre-competition scores for this age group, and will further investigate the capacity for K-D scores to capture closed head injury and concussion."

Dr. Balcer's advice is "to stay tuned!"

[Editor's note and update: Dr. Balcer's advice to stay tuned was appropriate: since this initial study, three more peer reviewed studies2,3,4 have confirmed that the KD test is a reliable tool for identifying possible concussion on the sports sideline.  See Related Articles].  


1. Galetta KM, Barret J, Allen M, et. al. The King-Devick test as a determinant of head trauma and concussion in boxers and MMA fighters. Neurology (2011); 76:1456-1462.


2. King D, Clark T, Gissanec C. Use of a rapid visual screening tool for the assessment of concussion in amateur rugby league: A pilot study. J. Neuro Sci . http://dx.doi.org/10.1016/j.jns.2012.05.049. 

3. King D, Brughelli M, Hume P, Gissane C.  Concussions in amateur rugby union identified with the use of a rapid visual screening tool.  J Neurol Sci 2013, http://dx.doi.org/10.1016/j.jns.2013.01.012 (published online ahead of print)(accessed February 14, 2013)

4. Galetta K, Brandes L, Maki K, Dziemiannowicz M, Laudano E., Allen M, Lawler K, Sennett B, Wiebe D, Devick S, Messner L, Galetta S, Balcer L. The King-Devick test and sports-related concussion: Study of a rapid visual screening tool in a collegiate cohort. J. Neuro Sci. 2011; 309(1):34-39.


Posted February 16, 2011; updated February 14, 2013