Background/Purpose: The concept of axial Spondyloarthritis (SpA) as defined by the ASAS criteria is relatively new. While the prevalence of Ankylosing spondylitis is around 0.5%, the exact prevalence of axial SpA in the general population is unknown. To evaluate the prevalence of axial SpA according to the ASAS classification criteria among the Israeli population of Jewish origin.

Methods: The study composed of 3 steps: 1) preliminary screening of the general population based on an internet screening survey of 4000 Israelis of Jewish origin, aged 18-45, which form a representative sample of the general population. Those answering positively to the question of suffering from lower back pain (LBP) for more than 3 months continued to the second step questionnaire. 2) step 2 comprised of 11 questions pertaining to inflammatory back pain (IBP) and other SpA features such as arthritis, enthesitis, uveitis, dactylitis, psoriasis, Crohn’s disease or colitis, and family history of SpA. Those who answered positively to at least one of the questions were invited to undergo further evaluation by a rheumatologist. Those who agreed moved to the 3rd step and were invited to the department of rheumatology. 3) the evaluation included a clinical form comprising the SpA features as specified in the ASAS criteria, imaging (X-RAY and MRI of the sacroiliac joints) and laboratory evaluation (CRP and HLA-B27).

Results: A total of 4012 people were screened via the internet survey. Of these, 1440 (36%) suffered from LBP for more than 3 months. 467 fulfilled the ASAS criteria for inflammatory back pain (32%) while 30-60% described at least one characteristic of inflammatory back pain, 11% arthralgia/arthritis, 12% dactylitis and 13% enthesitis. Four percent reported uveitis, 3.5% on psoriasis and 2% on Crohn’s disease or colitis. 1389 (35%) of them continued to step 2 and 981 (70%) answered positively to at least one of the SpA feature questions and were invited to be examined by a rheumatologist. 417 agreed and 60 kept their appointment. 3 patients were further excluded based on the exclusion criteria. HLA-B27 returned negative in all but one patient. The MRI showed findings compatible with sacroiliitis in 20 patients (active and/or chronic). Fifteen patients complied with the ASAS classification criteria for axial SpA resulting in an estimated prevalence of at least 0.4%.

Conclusion: The estimated prevalence of axial SpA is at least 0.4%. Taking into consideration the proportion of patients with IBP (6%), the prevalence is probably much higher and is between 0.4 and at least 1%. Internet screening for IBP may be a useful tool for detection of axial SpA.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/the-prevalence-of-axial-spondyloarthritis-in-israel/