The purpose of this study is to determine which of the proposed screening parameters or which combination of screening parameters perform best in daily clinical practice for making the diagnosis of axial Spondyloarthritis (SpA)in patients with chronic low back pain.

Ankylosing spondylitis (AS) and its early form accounts for up to 5% of all patients with chronic back pain. Shortening the delay of 5-10 years between first symptoms and making a diagnosis of AS has become a challenge especially because effective treatments have become available. Easy to apply referral parameters for physicians in primary care may contribute to make the diagnosis earlier.

Methods: Orthopedists and primary care physicians were offered to refer patients with i) chronic low back pain (duration >3 months) and ii) onset of back pain at an age < 45 years to a specialized rheumatology outpatient clinic for further diagnostic work-up if at least one of the following screening parameters was present: 1) inflammatory back pain (IBP), 2) positive HLA-B27, 3) sacroiliitis as detected by imaging. The final diagnosis was made according to expert opinion.

It was analyzed, which parameters or combination of parameters performed best in making a diagnosis of axial SpA.

Inclusion Criteria:

• chronic back pain with a duration of more than 3 months
• onset of back pain before age of 45 years

Exclusion Criteria:

• age younger than 18 years