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Comparison of two referral strategies for diagnosis of axial spondyloarthritis: the Recognising and Diagnosing Ankylosing Spondylitis Reliably (RADAR) study
  1. Joachim Sieper1,
  2. Shankar Srinivasan2,*,
  3. Omid Zamani3,
  4. Herman Mielants4,
  5. Denis Choquette5,
  6. Karel Pavelka6,
  7. Anne Gitte Loft7,
  8. Pál Géher8,
  9. Debashish Danda9,
  10. Tatiana Reitblat10,
  11. Fabrizio Cantini11,
  12. Codrina Ancuta12,
  13. Shandor Erdes13,
  14. Helena Raffayová14,
  15. Andrew Keat15,
  16. J S H Gaston16,
  17. Sonja Praprotnik17,
  18. Nathan Vastesaeger18
  1. 1Medical Department I, Rheumatology, Charite Campus Benjamin Franklin, Berlin, Germany
  2. 2Merck & Co, Inc, Kenilworth, New Jersey, USA
  3. 3Rheuma Zentrum Favoriten, Vienna, Austria
  4. 4Department of Rheumatology, University of Gent, Gent, Belgium
  5. 5Institut de Rhumatologie de Montréal, University of Montreal, Montreal, Canada
  6. 6Institute of Rheumatology, Prague, Czech Republic
  7. 7Vejle Hospital, Sygehus Lillebaelt, Vejle, Denmark
  8. 8Department of Rheumatology, Semmelweis University, Budapest, Hungary
  9. 9Clinical Immunology and Rheumatology, Christian Medical College, Vellore, India
  10. 10Barzilai Medical Centre, Ashkelon, Israel
  11. 11Hospital Misericordia e Dolce, Prato, Italy
  12. 12Grigore T. Popa University of Medicine and Pharmacy, Iasi, Romania
  13. 13Academy of Medical Science, Moscow, Russia
  14. 14National Institute of Rheumatic Diseases, Piest'any, Slovak Republic
  15. 15Northwick Park Hospital, Harrow, UK
  16. 16University of Cambridge, UK
  17. 17University Clinical Center Ljubljana, Ljubljana, Slovenia
  18. 18Merck Sharp and Dohme, Brussels, Belgium
  19. *SS current affiliation is Celgene Corporation, Summit, New Jersey, USA.
  1. Correspondence to Professor Joachim Sieper, Medical Department I, Rheumatology, Charite Campus Benjamin Franklin, Hindenburgdamm 30, Berlin 12200, Germany; joachim.sieper{at}


Objective To determine which of two referral strategies, when used by referring physicians for patients with chronic back pain (CBP), is superior for diagnosing axial spondyloarthritis (SpA) by rheumatologists across several countries.

Methods Primary care referral sites in 16 countries were randomised (1 : 1) to refer patients with CBP lasting >3 months and onset before age 45 years to a rheumatologist using either strategy 1 (any of inflammatory back pain (IBP), HLA-B27 or sacroiliitis on imaging) or strategy 2 (two of the following: IBP, HLA-B27, sacroiliitis, family history of axial SpA, good response to non-steroidal anti-inflammatory drugs, extra-articular manifestations). The rheumatologist established the diagnosis. The primary analysis compared the proportion of patients diagnosed with definite axial SpA by referral strategy.

Results Patients (N=1072) were referred by 278 sites to 64 rheumatologists: 504 patients by strategy 1 and 568 patients by strategy 2. Axial SpA was diagnosed in 35.6% and 39.8% of patients referred by these respective strategies (between-group difference 4.40%; 95% CI −7.09% to 15.89%; p=0.447). IBP was the most frequently used referral criterion (94.7% of cases), showing high concordance (85.4%) with rheumatologists' assessments, and having sensitivity and a negative predictive value of >85% but a positive predictive value and specificity of <50%. Combining IBP with other criteria (eg, sacroiliitis, HLA-B27) increased the likelihood for diagnosing axial SpA.

Conclusions A referral strategy based on three criteria leads to a diagnosis of axial SpA in approximately 35% of patients with CBP and is applicable across countries and geographical locales with presumably different levels of expertise in axial SpA.

  • Ankylosing Spondylitis
  • Spondyloarthritis
  • Treatment
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