Hello @lcmcphee -- Welcome to Connect. I can certainly understand why you would feel frustrated. Here is a link on Mayo Clinic's website that describes the Test ID: RNP -- RNP Antibodies, IgG, Serum:

-- https://www.mayomedicallaboratories.com/test-catalog/Clinical+and+Interpretive/81357

There is also a page on Mayo's website that discusses Primary biliary cholangitis (PBC) that may be helpful to read through the diagnosis & treatment along with the lifestyle and home remedies and more here:
-- https://www.mayoclinic.org/diseases-conditions/primary-biliary-cholangitis-pbc/diagnosis-treatment/drc-20376880

I'm also tagging @rosemarya to see if she might have some suggestions. She has posted in an old discussion about PBC but it hasn't had any new posts since 2012:
-- https://connect.mayoclinic.org/comment/4920/bookmark/e6250d439c9f868fc53ca3800e7a41d943be7dd0ecfdda6ae585394ec5df74d5/

@lcmcphee did the rheumatologist describe the symptoms that would make him think you have MTCD? I would ask him to tell you his reasons as this might prompt you for some more why questions. There's nothing wrong with getting a second opinion if you feel you are not getting answers.

John