This article was last reviewed on
This article waslast modified on 10 July 2017.

Tau protein (T-tau or total tau) is abundant in normal nerve cells and can be measured by immunoassay in cerebrospinal fluid (CSF), the fluid that bathes the brain and spinal cord. Concentrations of CSF tau protein increase following concussion, a usually mild brain injury that follows head trauma, causing brief unconsciousness and/or confusion, disturbed vision such as ‘seeing stars’ and loss of memory. Recovery is usually rapid and complete but occasionally symptoms last for weeks, months or longer. A blood test that could reflect the changes in the concentration of CSF tau protein might help diagnose and predict the course of concussion.

A study of concussion in 28 of 288 Swedish ice hockey players during the 2012 – 2013 season was published in online in JAMA Neurology on 13 March 2014. It introduced a new method (called ELISA single molecule array or ELISA Simoa™) that is over one thousand times more sensitive than conventional immunoassay for the extremely low levels of tau protein found in blood . The inventors and manufacturers of the test together with investigators at Sahlgrenska University Hospital, Mölndal, Sweden took base-line blood samples from 47 players in two of the 12 Swedish ice hockey teams before the start of the season. During the first half of the season, 35 of the 288 players sustained clinically diagnosed concussion; 28 of these had repeated blood samples taken at 1, 12, 36 and 144 hours after injury. Only three of the 28 had a short loss of consciousness but 15 still had symptoms at the time of the six day blood sample.

The main findings of the study were that the median concentration of tau protein l in the 28 players one hour after concussion was more than double that in the 47 pre-season players (although values overlapped) and that raised values persisted through the six day study period. The 15 players who still had symptoms at day six tended to have had higher one hour values than those without persistent symptoms. The first author, Dr Pashtun Shahim, commented that the researchers are continuing to add data as the season progresses. They hope the test can be developed to help sports physicians diagnose concussion and predict when those affected can safely return to play.

It is clearly important that these findings should be confirmed in sportsmen whose individual baseline tau protein values before concussion are known. An accompanying editorial commented that the numbers investigated were small and the follow-up period was rather short. It suggested that it is critical to know how long it takes plasma tau protein to return to normal and whether there is a time after which elevation persists. Goals for future studies should include achieving greater accuracy in the prediction of those with persistent symptoms, and determining whether elevated plasma tau protein identifies athletes who have sustained multiple mild concussions and are at risk of developing chronic brain damage.

Two of the authors of the study work for the firm that owns the new assay (Quanterix), and four are named as co-inventors in a US patent for tau as a blood biomarker for brain injury. The study was funded by the Swedish Medical Research Council.

See NHS Choices for more about concussion.