Immune antibody tests are already a standard part of a lot of mental health care, particularly psychosis. My wife tells me depending on the centre it may be mandated for all new diagnoses of psychosis. It is called an "organic screen".
I'm guessing that "organic screen" doesn't currently usually include antibody testing of CSF from a lumbar puncture since the article implies that only a limited number places do that screening currently.
> To find psychiatric patients who might benefit from immunotherapy, researchers have set up centers, roughly similar to the one at Columbia, at Baylor University Medical Center, in Texas; King’s College London; Uppsala University, in Sweden; and the University of Freiburg, in Germany, among other places. Some of the best research into the phenomenon has been conducted in Germany, where it’s more common for patients in a first episode of psychosis to have lumbar punctures to access their spinal fluid, which can reveal the presence of antibodies.
