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The King-Devick Test for Concussion Evaluation: What Questions Should We Be Asking?

Claudia Percifield, MS, ATC

The King-Devick Test is a vision-based concussion assessment tool, which has been previously used to identify a variety of other medical conditions and learning disabilities.

1.   Who is this test appropriate for?

The simplicity of the testing (reading numbers) means a much younger demographic could successfully follow the instructions for the King-Devick Test, making it a much more universal testing option.  However, this test is completely dependent on having an available baseline measurement for comparison.  This would mean all teams, in all sports, would need to perform this as a baseline and keep the results on them at all times.  Is this feasible?

2.   How frequently do baseline scores become obsolete?

The Centers for Disease Control and Prevention (CDC) recommends baseline testing for other concussion testing annually, with neuropsychological testing performed at least every 2 years.  With brains that are constantly developing, how quickly will athletes outperform their baseline of the King-Devick Test, even after suffering a concussion?

3.   What happens if the test gets interrupted due to the job demands of an Athletic Trainer?

While the King-Devick test only takes 1-2 minutes to administer, a selling point compared to the SCAT3 exam, what happens when another athlete is down on the field or even requiring wound care?  This test is completely dependent on your focus and timing as the administrator to provide accurate results of how the athlete performs.  In a setting where medical staff is abundant, there will be no issue with administration; but at the high school level, one Athletic Trainer may be the sole person responsible for multiple events and practices at multiple venues simultaneously.  Will you be able to rely on this test as heavily?  Should you rely on others to administer this exam?  And if you do, how seriously will the athletes take it?

4.   What about athletes who do not wear corrective lenses for sport but may need them for reading?

If worn for baseline testing, but not sport, this is easily a confounding variable with on the field assessment.

5.   What about confounding factors such as dehydration, facial trauma, dyslexia, other reading delays, etc.?

In a day and age where people are highly sensitive to their concussion number, false positives may be another concern.  One researcher noted in Neurology Now that the exertion level an athlete exhibits in sports can affect the outcomes of neurological exams regardless of injury or illness status.  For those athletes who are also exhausted or in a dehydrated state, wouldn’t impaired performance be noted as well?  Additionally, instructions for the King-Devick Test state that the athlete cannot use their finger to follow the pattern.  Some young readers or readers with learning impairments may struggle more with the exam under these instructions.  How does this affect how we interpret the results?

6.   What is the best way for this test to be implemented into our practice?

Some media outlets are calling for the King-Devick to be the test in concussion diagnosis.  The research indicates the support for that decision isn’t scientifically  there yet.  Should this be a supplemental initial screening tool, with those who demonstrate impairment, then follow up with a SCAT3?  Or do we wait until there’s more evidence-based research to support the appropriate implementation of the King-Devick Test?

7.   Are we trying to over-simplify concussions?

As clinicians, we all agree properly diagnosing and managing concussions is paramount to athletes’ safety.  We’re constantly searching for tools that work to make an injury filled with gray more black and white.  Are we too quick to jump on the band wagon because of the current concussion climate?

Resources:

King-Devick Test Website: http://www.kingdevicktest.com

Neurology Now, June/July 2014 Volume 10(3)p 12–1, Accessed online: http://patients.aan.com/resources/neurologynow/index.cfm?event=home.showArticle&id=ovid.com%3A%2Fbib%2Fovftdb%2F01222928-201410030-00011

Centers for Disease Control and Prevention: http://www.cdc.gov/headsup/basics/baseline_testing.html

New York Times: http://well.blogs.nytimes.com/2015/03/11/a-2-minute-test-to-detect-concussions/?_r=0