Diagnosing concussion: liquid biopsy is changing the game

Rugby, along with many other contact sports such as football, boxing and American football, has come under increased scrutiny in recent years over its handling of the repetitive head and neck trauma which its players are prone to, as the link between head injuries and the risk of neurodegenerative diseases such as dementia, Alzheimer’s and Parkinson’s becomes ever clearer. Particular focus has been directed to the consistency of concussion diagnosis protocols, with a need for an objective and accepted definition of concussion which can be used during matches to identify and substitute concussed athletes. Fans watching the recent Six Nations tournament have become accustomed to seeing players removed from the fray for head injury assessments (HIAs), which are currently the ‘gold standard’ for diagnosing concussion during rugby matches. However, a new approach pioneered by researchers at the University of Birmingham has identified a method of diagnosing concussion using a simple saliva sample.


The aptly named Study of Concussion in Rugby Union through MicroRNAs (SCRUM), published in the British Journal of Sports Medicine identified a series of small, noncoding RNAs (sncRNAs) in saliva which can be used as a diagnostic signature for concussion. The researchers collected saliva samples from 1028 male professional rugby players from the top two tiers of English rugby. Samples were collected at three time points: during HIAs, post-match and 36-48 hours post-match, as well as control samples and pre-season samples. 32 diagnostic sncRNAs were identified as having differential expression across the three time points in players with a positive clinical diagnosis of concussion following a HIA when compared with those who passed the HIA test and were cleared of concussion.

The study shows that a subset of 14 of these sncRNA biomarkers could be used to predict clinical diagnosis of concussion in the professional rugby players. In this setting, the obvious importance of preventing all concussed athletes returning to play (high sensitivity) is balanced with the importance of avoiding false positives which would remove uninjured players from play unnecessarily (high specificity). The area under the curve (AUC) achieved in this study of 0.96 is a good indication that this test has suitable performance characteristics.

Revolutionising how diagnosis of concussion is approached in sport

The advantages of the stability of sncRNAs, along with the straightforward and non-invasive acquisition of saliva as a liquid biopsy, opens the door to the development of a diagnostic test which could revolutionise the approach to the diagnosis of concussion in sport. The testing carried out in the study relies on lab-based PCR analysis of saliva samples, meaning the next step is converting this test into a more practical format for pitch-side use. Marker Diagnostics are in the process of commercialising the diagnostic test as an over-the-counter product which would provide a rapid diagnosis without the need for laboratory analysis.

While the study consisted entirely of male professional rugby players, the authors note that the potential applications of their findings reach far beyond rugby, or professional sport in general. While heavily scrutinised, professional team physicians are highly skilled and well trained to carry out HIAs, while at grass-roots level the access to such trained healthcare professionals is far more limited. Therefore, it is in the non-professional sport setting that the saliva-based diagnosis could have the most impact. Further work is underway to validate the results in younger individuals and non-professional athletes as well as in female athletes, who were not part of the present study. Additionally, the sncRNAs identified could help to elucidate the pathophysiology of concussion and drive future improvements in the treatment of the condition.

The data provide yet another indication of the vast diagnostic potential of liquid biopsies (see our blog Minimally invasive, maximum potential: liquid biopsy is redefining diagnosis), while reassuring fans and players of rugby that it will be possible to mitigate the dangers of concussion without losing the physicality and intensity which define the sport.