Hi , I'm really sorry you're going through this. It can be extremely confusing and unsettling when doctors don't agree on a diagnosis. Did the second doctor say why they thought you didn't have psoriatic arthritis (or what they thought you did have instead)?
Unfortunately, there isn't one specific test that can tell you for sure that you have psoriatic arthritis. There are, however, a number of assessments (blood and imaging tests, medical/family history, and a physical exam) that can help build a picture of what's going on. The following article looks at the diagnostic process for psoriatic arthritis: https://psoriatic-arthritis.com/how-doctor-diagnose We also have an article on common symptoms of PsA, which I thought might be of interest: https://psoriatic-arthritis.com/psa-symptoms I really hope this is of some help.
Do you have a plan going forward? Please remember that we're here anytime you have questions or need support. Hugs! -Catherine, Community Moderator