King-Devick Test Time Varies by Testing Modality

Objective: To explore differences in baseline King-Devick Test (KD) completion time between 2 testing modalities: (1) spiral-bound paper cards (cards) and (2) iPad application (iPad). Design: Cross-sectional cohort analysis. Setting: National Collegiate Athlete Association (NCAA) institutions. Participants: Student athletes from 13 women's and 11 men's collegiate sports who completed KD baseline testing as part of their first year in the Concussion Assessment, Research and Education (CARE) Consortium from 2014 to 2016 (n = 2003, 52.2% male). Independent Variables: King-Devick Test modalities; cards or iPad. Main Outcome Measure: Baseline KD completion time (seconds). Results: Mean baseline KD completion time of the iPad modality group [42.8 seconds, 95% confidence interval (CI), 42.1-43.3] was 2.8 seconds (95% CI, 2.1-3.4) greater than the cards group (40.0 seconds, 95% CI, 39.7-40.3) (t(1, 1010.7) = -8.0,P< 0.001, Cohen'sd= 0.41). Conclusions: Baseline KD performance is slower when tested on an iPad than when tested on spiral-bound paper cards. The 2 KD modalities should not be used interchangeably in concussion assessments because differences in the modalities can lead to time differences similar in magnitude to those used to indicate concussion. From a research perspective, modality may influence interpretation and/or synthesis of findings across studies.