• To determine which of the referral criteria proposed, or which combination of referral criteria, is the most successful and workable in the diagnosis of AS when used by referring physicians. [ Time Frame: Approximately 3-6 months ] [ Designated as safety issue: No ]
• To describe the demographics and disease characteristics of patients diagnosed with AS. [ Time Frame: Approximately 3-6 months ] [ Designated as safety issue: No ]
• To compare patient-derived data with physician data to determine whether the former alone can serve as effective screening for AS. [ Time Frame: Approximately 3-6 months ] [ Designated as safety issue: No ]

This is a multi-national, multi-site, observational study to determine which of two strategies, when used by referring physicians is superior in the diagnosis of axial spondyloarthritis (AS) by rheumatologists.

Subjects will be selected using a non-probability sampling method. For each center of excellence, the local network of referring physicians will be assigned, according to a random code in a 1:1 ratio, to use one of the two referral strategies for eligible patients.

• Spinal Spondyloarthropathies
• Axial Spondyloarthritis

• Patient meets at least one of the following three criteria:

  1. Inflammatory back pain
  2. Human leukocyte antigen B27 (HLA-B27)
  3. Sacroiliitis demonstrated by imaging (X-ray, magnetic resonance imagining [MRI], bone scan [if previously available])

• Patient meets at least two of the following six criteria:

  1. Inflammatory back pain
  2. HLA-B27
  3. Sacroiliitis (on imaging)
  4. Family history of AS
  5. Good response of back pain to nonsteroidal anti-inflammatory drugs (NSAIDs)
  6. Known Extra Articular Manifestations (Uveitis, Iridocyclitis, Psoriasis, Inflammatory Bowel Disease)

Inclusion Criteria:

• A subject must have back pain of unknown origin, of more than 3 months' duration, and with onset before age 45.
• A subject must be willing to give written informed consent and be able to adhere to visit schedules.

Exclusion Criteria:

• Established diagnosis of spondyloarthropathies at the time of referral.
• Any clinically significant condition or situation, other than the condition being studied, that, in the opinion of the investigator, would interfere with the study evaluations or optimal participation in the study.