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CARE Consortium: King-Devick test time varies by testing modality

Study finds differences between test results when administered via paper or electronically

The King-Devick test, a timed exam that requires participants to identify and name numbers rapidly in order to gauge eye movement and reaction time, has become an important tool for clinicians evaluating concussions. It can be administered via spiral-bound paper cards or digitally via devices such as iPads. But are the two testing modalities comparable, or might results differ based on the method used? To seek an answer, Dr. James Clugston, an associate professor at the University of Florida College of Medicine, and a team of researchers examined test results from more than 2,000 student-athletes taking part in the NCAA-Department of Defense Concussion Assessment, Research and Education Consortium study. Their findings were published in the Clinical Journal of Sport Medicine.

What did the study find?

During baseline tests, it took student-athletes 2.8 seconds longer, on average, to complete the King-Devick test on an iPad. That result held true across a range of demographic categories and sports.

What are the implications?

Because baseline testing times are consistently slower on iPads, the testing modalities should not be used interchangeably in an effort to diagnose concussion or gauge recovery. The differences between the two testing methods suggest using them interchangeably could lead to an incorrect diagnosis. “Clinicians should administer baseline and post-injury assessments using the same modality because differences in the modalities alone can lead to differences of time that are similar in magnitude to those used to indicate concussion,” the paper noted.

What’s next?

While the implications from a clinical perspective are relatively clear, researchers relying on King-Devick test results in the future should note that the testing modality may influence their findings, particularly when comparing previous studies that have used the King-Devick test but may have relied on a different modality.