Study Confirms Practice Effect for King-Devick Test, Finds Both Age and Sex Influence Time To Completion

A new study has identified a substantial practice effect among a population of healthy young athletes taking the King-Devick (KD) test, a concussion screening tool used to by medical professionals to detect impairment of eye movements, attention, and language, and that both age and sex of the participant also influenced test scores. (1)

The study comes on the heels of the presentation of research at the annual meeting of the American College of Sports Medicine (2) questioning whether it was appropriate to consider use of KD as a best practice in the identification and management of sports-related concussion based on concerns about the test’s “relatively poor” ability to correctly identify as concussed athletes who were not diagnosed as having suffered concussions.

While finding excellent test-retest reliability, the researchers reported a statistically significant 5.25 second decrease in the total time 60 young athletes, ages 14 to 24, took to read aloud a series of single-digit numbers from left to right on the first series of three test cards to the time to completion on the third three-card test, with most of the improvement (3.53 seconds) from trial 1 to trial 2.

For each 1-year increase in age, they found that the mean KD composite score decreased by 2%, with age accounting for 5% of the variability in time to completion. The mean time to completion for females was seven seconds longer than for males.

The findings prompted the authors to recommend that three KD trials be performed, with the first trial considered a practice test, in order to provide a more accurate KD composite score for use by health care professionals, and that the sex and age of the athlete needed to be considered if KD is used as a concussion screening tool.

“The current study highlights the importance of precise and thorough baseline testing to assist a health care professional with clinical decision-making if there is a subsequent concussion,” wrote lead author, John Heick, an associate professor in physical therapy at the Arizona School of Health Sciences at A.T. Still University in Mesa, Arizona.

Because the data was collected under optimal circumstances in a controlled laboratory environment, with “no guarantee” that the findings would translate into a “real life, clinical scenario,” Heick said that the findings “should be interpreted only as an early step in the validation of the King-Devick test for clinical use with young patients who potentially have concussion.”

Given the large difference in times between males and females, further study, said Heick, would also be required if KD was to be used as a clinical measure to identify oculomotor dysfunction among female athletes.

Finally, because the participants were not selected to represent an athletic population, and could not therefore be generalized to other athletes, Heick said further study would be required to investigate “how many trials are needed to establish a performance plateau in multiple athletic populations” and to determine if practice effects differ among different athletic groups.

Heick JD, Bay C, Dompier TP, Valovich McLeod TC. The Psychometric Properties of the King-Devick Test and the Influence of Age and Sex in Healthy Individuals Aged 14 to 24 Years. Ath Tr. and Sports Health Care. 2016; DOI: 10.3928/19425864-20160509-01 (e-published June 8, 2016).
MacDonald J, Kyroac D, Peterson I. Reliability and Specificity of the King-Devick Test in Baseline Concussion Evaluations of High School Athletes. Research poster presented at 2016 American College of Sports Medicine Annual Meeting, Boston, MA, June 2016.

New Research Questions Accuracy of King-Devick Test As Sideline Concussion Screening Tool