Concussions in the National Football League: the evolution of video review for assessing the frequency and reliability of visible signs.

: The use of video review to document visible signs (VS) of sport-related concussion in the National Football League (NFL) is a novel method to recognize head injuries. : The current pilot studies used varying methodologies to (1) examine the frequency of VS in concussed NFL players using the Australian Football League's (AFL) checklist, and (2) assess the reliability of VS between non-expert and expert raters. : Cohort study : In the first pilot study, two rated VS of SRC occurring in the 2015 NFL season (96) using a single VS from the AFL checklist. Based on this pilot study, two then rated VS of SRC during the 2017 NFL season (211) using all VS from the AFL checklist. The frequency, total percent agreement (TPA), and reliability (kappa coefficients) were calculated for all VS of concussion for the two seasons. Kappa agreement was classified as fair (.41-.60), moderate (.61-.80), or substantial (.81-1.00). Significance was set at .05. : The most frequent VS of concussion identified by both non-expert and expert raters were . The least frequent VS were , the average TPA for VS ranged from 84% to 100% and kappa coefficients ranged from .52 to .68. For , the average TPA ranged from 83% to 100%, and kappa coefficients ranged from .56 to .86. : In these preliminary analyses, use of multiple VS was a superior methodology, and the reliability of VS rating was stronger for experts. Due to the inherent differences in gameplay and protective equipment used in the NFL compared to other professional sports, it is our hope these data can generate new ways to improve existing practices and identify potentially novel VS of SRC.