A simple blood test may be the key to knowing if an athlete is ready to return to play following a concussion.  A new Swedish study finds measuring the level of a specific protein in the blood may not only reveal a concussion, but also when an athlete's brain has healed.

"The main finding of the study is to underscore the necessity of biomarkers in the treatment, prevention, and diagnosis of concussion," said Dr. Damir Janigro, who did not take part in this particular study but studies concussion at Cleveland Clinic's Lerner Research Institute.

Researchers at Sahigrenska University studied 280 professional hockey players in Sweden.  35 of them suffered a concussion during the season and were given blood tests at 1, 12, 36, and 144 hours after it happened.

Results show players who were concussed had an increased level of the protein t-tau. In fact, researchers say the higher the level, the longer it took for symptoms to resolve.

The study's authors suggest checking t-tau levels may be a good way to diagnose a concussion and may also help determine when an athlete is ready to return to play. Janigro says the findings are a good first step.

"I think this is a starting point to develop a panel of blood tests that will allow us to diagnose and prognose, meaning predict the future in a way, of what a concussed player should do next," said Janigro.

Read more about this study in JAMA Neurology.