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Spondyloarthritis
Original article
Diagnostic accuracy of inflammatory back pain for axial spondyloarthritis in rheumatological care
  1. Denis Poddubnyy1,
  2. Johanna Callhoff2,
  3. Inge Spiller1,
  4. Joachim Listing2,
  5. Juergen Braun3,
  6. Joachim Sieper1 and
  7. Martin Rudwaleit4
  1. 1 Department of Gastroenterology, Infectious Diseases and Rheumatology, Campus Benjamin Franklin, Charité Universitätsmedizin Berlin, Berlin, Germany
  2. 2 Epidemiology Unit, German Rheumatism Research Centre, Berlin, Germany
  3. 3 Department of Rheumatology, Rheumazentrum Ruhrgebiet, Herne, Germany
  4. 4 Department of Medicine and Rheumatology, Klinikum Bielefeld Rosenhöhe, Bielefeld, Germany, Charité Universitätsmedizin Berlin, Berlin, Germany, and Gent University, Gent, Belgium
  1. Correspondence to Dr Martin Rudwaleit; martin.rudwaleit{at}klinikumbielefeld.de

Abstract

ObjectiveInflammatory back pain (IBP), the key symptom of axial spondyloarthritis (axSpA), including ankylosing spondylitis, has been proposed as a screening test for patients presenting with chronic back pain in primary care. The diagnostic accuracy of IBP in the rheumatology setting is unknown.

Methods Six rheumatology centres, representing secondary and tertiary rheumatology care, included routinely referred patients with consecutive chronic back pain with suspicion of axSpA. IBP (diagnostic test) was assessed in each centre by an independent (blinded) rheumatologist; a second (unblinded) rheumatologist made the diagnosis (axSpA or no-axSpA), which served as reference standard.

Results Of 461 routinely referred patients, 403 received a final diagnosis. IBP was present in 67.3%, and 44.6% (180/403) were diagnosed as axSpA. The sensitivity of IBP according to various definitions (global judgement, Calin, Berlin, Assessment of SpondyloArthritis international Society criteria for IBP) was 74.4%–81.1 % and comparable to published figures, whereas the specificity was unexpectedly low (25.1%–43.9%). The resulting positive likelihood ratios (LR+) were 1.1–1.4 and without major differences between sets of IBP criteria. The presence of IBP according to various definitions increased the probability of axSpA by 2.5%–8.4% only (from 44.6% to 47.1%–53.0%).

Conclusions The diagnostic utility of IBP in the rheumatology setting was smaller than expected. However, this was counterbalanced by a high prevalence of IBP among referred patients, demonstrating the effective usage of IBP in primary care as selection parameter for referral to rheumatology. Notably, this study illustrates potential shifts in specificity and LR+ of diagnostic tests if these tests are used to select patients for referral.

  • spondyloarthritis
  • low back pain
  • ankylosing spondylitis
  • epidemiology

This is an open access article distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited, appropriate credit is given, any changes made indicated, and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0

https://doi.org/10.1136/rmdopen-2018-000825

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    Footnotes

    • Collaborators Jan Brandt, Klaus Krüger, Kirsten Karberg, Dorothea Pick, Florian Schuch, Jörg Wendler.

    • Contributors All authors contributed to acquisition, analysis and interpretation of the data and drafting the manuscript.

    • Funding This work was supported by a research grant from the German Research Foundation (Deutsche Forschungsgemeinschaft(DFG)), GZ RU 681/5-1.

    • Competing interests None declared.

    • Patient consent Obtained.

    • Ethical approval The study was approved by the ethics committee of the Charité Universitätsmedizin Berlin, and thereafter in the respective institutions of all participating centres.

    • Provenance and peer review Not commissioned; externally peer reviewed.

    • Data sharing statement No additional data are available.