The King–Devick (K–D) test is often used as part of a multimodal assessment to screen for sport-related concussion. However, the test involves reading numbers, and little is known about variation in baseline performance on the K–D by reading skill level. We conducted a cross-sectional study analyzing data from the Concussion Assessment, Research and Education (CARE) Consortium to assess differences in baseline performance on the K–D associated with factors that impact reading skill level (learning disorder [LD] and primary home language other than English [PHLOTE]), while controlling for covariates (gender, type of sport, attentional issues, history of concussion and modality of administration). We had a sample of 2311 student-athletes (47% female), and multivariate regression indicated an average K–D performance time of 40.4 s. Presence of LD was associated with a 3.3 s slower K–D time (95% CI 1.9–4.7, p < 0.001), and PHLOTE was associated with a 2.6 s slower K–D time (95% CI 1.2–4.0, p < 0.001), after controlling for other covariates. These results suggest caution in the use of normative data with the K–D. Future studies should explore the impact of factors associated with reading skill level on sensitivity of the K–D in detecting concussion.
Summary Points:
- The King–Devick (K–D) test has been used as a rapid sideline screening test, since it evaluates complex cognitive function including visual-motor coordination, language function and attention, and thus sensitive to concussion and other brain injury.
- Multiple regions of the brain are necessary to complete the K–D test. Motor function is involved, particularly saccades (scanning from left to right across the page in a coordinated fashion) and accommodation (contracting the eye muscles in order to focus on and read the numbers). The amplitude of saccadic eye movement is associated with the oculomotor nuclei, whereas the direction of these eye movements is associated with the reticular formation. Individuals completing the K–D must also recognize single digit numbers, a function that has been localized to the inferior temporal gyrus. They must then associate each number with the English word for that number and contract the oral musculature to say the word for each number aloud, which involves both language comprehension (Wernicke’s area) and language production (Broca’s area).
- Multiple regression analysis including presence of LD and PHLOTE (primary home language other than English) in addition to other covariates had the best model fit, and indicated a 3.3 s longer K–D performance time for those with LD (95% CI 1.9–4.7, p < 0.001) and 2.6 s longer K–D time (95% CI 1.2–4.0, p < 0.001) for those with PHLOTE.
- These results suggest caution in using normative data with the K–D test, as these factors may result in false positive findings in the absence of concussion.