As Dr. Schneider said, it is very much a clinical diagnosis. We don't have any objective testing for concussion that can do this definitively. There's no gold standard.
Take surgery for knee injuries, for example. That would be the gold standard. You can actually go in and see that a ligament is torn. You can confirm that as a diagnosis. There's no way right now to confirm that a concussion has happened, so we don't have a gold standard. It's very much a clinical diagnosis. The injury occurred and there was some sort of mechanism of injury, followed shortly thereafter by the onset of symptoms.
There are tests out there. As Dr. Schneider said, any one test used in isolation is not helpful. However, combining them into a battery of tests, if you will, can add some insight into the picture. However, there are some challenges with that still.