Sure, but I wanted to clarify for anyone reading the comments that you can have psoriatic arthritis without psoriasis. That is part of what makes PsA hard to diagnose and to distinguish from RA.

I believe you that there are tests for inflammatory markers, but there are also antibody tests, including RF. Here is a quote from rheumatoidarthritis.org:

> “In most cases of rheumatoid arthritis, the patient tests positive for rheumatoid factor (RF) and/or anti-citrullinated peptides (CPP) antibodies.”

They have a whole page about the RF blood test, so I don’t know what else to tell you. I’m not a physician.