SAT0265
RATIO OF NON-RADIOGRAPHIC AND RADIOGRAPHIC AXIAL SPONDYLOARTHRITIS IN PATIENTS REFERRED BECAUSE OF BACK PAIN IS DEPENDENT ON SYMPTOM DURATION
D. Poddubnyy 1,*H. Brandt 1J. Vahldiek 1I. Spiller 1I.-H. Song 1M. Rudwaleit 2J. Sieper 1
1Charité Universitätsmedizin Berlin, 2Endokrinologikum, Berlin, Germany
Background: Non-radiographic axial spondyloarthritis (nr-axSpA) and radiographic axial SpA (=ankylosing spondylitis – AS) are considered currently as two stages of axial SpA. We reported recently that about 12% of the patients with non-radiographic axial SpA progress in AS over 2 years [1]. Although it can be expected that in the first years after back pain onset non-radiographic (without definite sacroiliitis on the x-ray) SpA is more likely to see than established AS, their frequencies and their ratio in relation to back pain duration at the referral time point is not known.
Objectives: To estimate the ratio of nr-axSpA and AS diagnoses in relation to the symptom duration in patients referred to a rheumatologist because of chronic back pain and suspicion of axial SpA.
Methods: In this monocenter study performed in Berlin [2] orthopaedists and primary care physicians were requested to refer patients with chronic low back pain (duration >3 months) and onset of back pain before <45 years of age to a SpA-specialized rheumatology outpatient clinic for further diagnostic investigation if at least one of the following screening parameters was present: 1) inflammatory back pain, 2) positive HLA-B27, and 3) sacroiliitis detected by imaging. The final diagnosis was made according to the opinion of rheumatologist.
Results: In total, 522 patients were referred. A diagnosis of definite axial SpA was made in 43.7% of the cases. Among patients who were referred with chronic back pain axial SpA was diagnosed in a similar percentage of about 50% if symptom (back pain) duration was <9 years and of 36% if symptom duration was >9 years. The ratios of nr-axSpA to AS among patients with definite axial SpA in relation to the duration of back pain at the time-point of referral are presented in figure. Nr-axSpA represented the majority of patient (67.3%) only if duration of back pain was 1 year and less at the time of referral. Between 1 and 6 years of back pain duration the probability of nr-axSpA and AS was nearly equal. In patients with back pain duration of more than 6 years, AS was more likely to be diagnosed than nr-axSpA, and this increased further over time.
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Conclusions: Non-radiographic axial SpA is a relevant diagnosis in patients with axial SpA at any time point, however, the probability of non-radiographic form of axial SpA is highest if symptom duration is short.
References: 1. Poddubnyy D, et al. Ann Rheum Dis 2011;70:1369-74. 2. Brandt HC, et al. Ann Rheum Dis 2007;66:1479-84.
Disclosure of Interest: None Declared