Abstract: The present invention relates generally to methods for diagnosing the presence or the risk of development or the therapy control of spondyloarthritis (Spa), in particular, of ankylosing spondylitis (AS) and undifferentiated spondyloarthritis in a subject, in particular in mammals. In addition, the present invention relates to test kits for use in the diagnosis of the presence or the risk of development, or for the therapy control of Spa, like AS and undifferentiated spondyloarthritis, in a subject. In particular, the present invention relates to a method for diagnosing the presence or the risk of development, or for the therapy control of Spa, like AS and undifferentiated spondyloarthritis, in a subject analysing for the presence of autoantibodies against CD74 and/or IKBKB in a subject. The presence of autoantibodies against CD74 and/or IKBKB is indicative for the presence or the risk of development, or for the therapy control of Spa, like AS and undifferentiated spondyloarthritis.