The article does not describe the protein. The S-100b protein has been studied years ago. It is an indicator but it sounds like the test is expensive because I only see it mentioned in research situations, not in treatment modalities. There are also tests for Tau protein that can indicate a problem.

The background link does not work so no background information is available.

The kidneys filter out protein and protein metabolites. They can become over-whelmed by too much protein.