Résumé : Currently, there is a 5 to 7 years gap between the first symptoms and the diagnosis of ankylosing spondylitis. A better patient referral might reduce this gap and accelerate the adequate treatment implementation. The study objective was to compare 2 referral strategies used in first line. In Belgium, 208 referral physicians assigned to 16 rheumatology centres were randomized to refer chronic back pain patients (with onset <45 years) using 1 of the 2 referral strategies : Strategy 1 :1 of 3 criteria (inflammatory back pain, HLA-B27, sacroiliitis on imaging); or Strategy 2 : 2 of 6 criteria (IBP inflammatory back pain, HLA-B27, sacroiliitis, family history, good response to NSAIDs, extra-articular manifestations). Among the 141 refer red patients with strategy 1 and 2, 26.0 and 36.9% respectively were diagnosed with Axial Spondylarthritis (SpA). Inflamma tory back pain, sacroiliitis and good respond to NSAIDs were the most frequently used criteria (92.9%, 36.2% and 33.3% respectively). This study emphasizes the high prevalence of undiagnosed axial SpA in patients with chronic back pain and stressed the necessity to increase awareness of the disease.