Objective To review the sensitivity and specificity of the proposed international consensus on-field visible signs of concussion in a cohort of National Rugby League (NRL) players.

Design Prospective cohort study.

Setting National Rugby League (NRL).

Participants National Rugby League (NRL) players.

Procedure The international consensus on-field video signs of concussion were coded for every head impact event (HIE) during the 2019 NRL season.

Outcome Measures Diagnosed concussion and the six international consensus on-field video signs.

Main Results There were 943 HIEs identified during the 2019 NRL season, of which 106 resulted in a diagnosed concussion. The most frequently observed sign in concussed athletes was blank/vacant look (54%), while the most sensitive was tonic posturing (57%), and the most specific was impact seizure (99%) and lying motionless (99%). In 41.8% of diagnosed concussions none of the signs were observed on video review. The six proposed international consensus signs demonstrated ‘fair’ ability to discriminate between concussion and non-concussion HIEs (AUC=0.76).

Conclusions International consensus agreement between collision sports for the on-field signs of concussion and the definition of those signs are clinically important, however the selection of signs requires rigorous assessment to examine their predictive value across all sports and within individual sports. Based on these findings, the use of video signs alone is not considered to be an appropriate clinical strategy, rather the signs may provide the medical officer with supportive information for making a medical decision.