I have had the same UC result for the Prometheus and also some uncertainty regarding the diagnosis, though the pathologists tend to be 90%+ sure I have UC... however they mostly all consider the Prometheus useless and inaccurate. I think the fact that they can't be 100% sure, or at least 99%, is one of the many factors that keeps me hanging on... but like you I am leaning toward colon removal pretty soon. (I won't have a choice if I can't get off prednisone in any case).
Pancolitis ~20 years, once had a full med-free 10 year remission,
but flaring/simmering on and off for years, allergic to all 5ASAs
15ish mg pred,
100 mg Imuran TCM
Probiotics (PD, Cust.Probiot., Culturelle, VSL3, etc), DMSO,
boswellia, fish oil, many vits/minerals
Lower-carb version of Specific Carb Diet (SCD), Remicade newbie