Abstract

Background: 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: Orthopaedists 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.

Results: 350 referred cases were analysed. A diagnosis of definite axial spondyloarthritis (axial SpA) comprising established AS and pre-radiographic axial SpA could be made in 45.4% of all referred patients, 50.3% of these were classified as AS and 49.7% as pre-radiographic axial SpA, 45.4% were classified as non-SpA, and 9.1% as possible SpA. If only one referral parameter was positive, a diagnosis of definite axial SpA was made in 34.2% and if more than one parameter was positive in 62.6%.

Conclusions: The proposed referral parameters have proven useful when applied in primary care in identifying patients with AS/pre-radiographic axial SpA among young to middle-aged patients suffering from chronic low back pain.