This is probably one of the best articles I've ever come across which so accurately addresses the Dx of Spondyloarthritis. There are excellent flow charts and decision trees and probability charts based on specific symptoms.
The family of Spondyloarthritis includes" Ankylosing Spondylitis, Reactive Arthritis, arthritis/Spondylitis with Inflammatory Bowel Disease, Psoriatic Arthritis and undifferentiated Spondyloarthritis. Also Spondylitis is interchangable with Spondyloarthritis.
Sometimes, you can access the entire article through the website I'll list, but other times, you may need to register for free access. I have the article in a .pdf file and would be happy to emai lit to anyone who can't access it on their own. Just click the envelop under my name to send me an email and I'll send the file ASAP.