There is a blood test for Autoimmune autonomic ganglionopathy - ganglionic Acetylcholine receptors antibodies.
It can be done at Mayo clinic as a part of there paraneoplastic evaluation (http://www.mayomedicallaboratories.c...rpretive/89904)
or much cheaper at Oxford labs (http://www.ouh.nhs.uk/immunology/dia...ntibodies.aspx).

There is a good lecture about it at mayo’s web site -
http://www.mayomedicallaboratories.c...12/07-autodys/