Really you should post more information to be sure of this

i.e.

what are they testing for
what is the medical condition involved
etc

Tau protein (β transferrin or asialo-transferrin) - University of ...
www.birmingham.ac.uk › ... › Neuroimmunology › Other Services
Tau protein (ß transferrin or asialo-transferrin) is present in cerebrospinal fluid (CSF) and is used as a marker for the identification of CSF ... United Kingdom.