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Original Article

Prevalence of axial SpA in US rheumatology practices: Assessment of ASAS criteria vs. rheumatology expert clinical diagnosis

  1. Vibeke Strand (MD)1,
  2. Sumati A. Rao (PHD)2,†,*,
  3. Alicia C Shillington (PHD)3,
  4. Mary A. Cifaldi (PHD MSHA, RPH)2,
  5. Michael Mcguire (PHARMD)4,
  6. Eric M. Ruderman (MD)5

DOI: 10.1002/acr.21994

Additional Information

Author Information

  1. 1

    Division of Immunology/Rheumatology, Stanford University School of Medicine, Palo Alto, California, United States

  2. 2

    AbbVie Inc., North Chicago, Illinois, United States

  3. 3

    EPI-Q Inc, Oak Brook, Illinois, United States

  4. 4

    Medical Data Analytics, Parsippany, New Jersey, United States

  5. 5

    Division of Rheumatology, Northwestern University Feinberg School of Medicine, Chicago, Illinois, United States

  1. †

    USAPhone: (847) 938-0874 Fax : (847) 937-1992

*AbbVie, Inc., 1 N Waukegan Road, D-GMH1, AP31-1 NE, North Chicago, IL 60064,

  1. †

    USAPhone: (847) 938-0874 Fax : (847) 937-1992

Publication History

  1. Accepted manuscript online: 22 FEB 2013 10:51AM EST
  2. Manuscript Accepted: 13 FEB 2013
  3. Manuscript Revised: 6 FEB 2013
  4. Manuscript Received: 22 AUG 2012

Funded by

  • AbbVie

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Abstract

Objective.

New classification criteria for axial spondyloarthritis (SpA) have been validated by the Assessment of SpondyloArthritis international Society (ASAS) working group. We applied these criteria to estimate prevalence of SpA in randomly selected, retrospectively reviewed medical records from representative US rheumatology practices.

Methods.

Rheumatologists from 101 US practices identified at-risk patients aged 18 to 44 years with chronic back pain.Medical records were reviewed against ASAS criteria. The proportion of patients meeting ASAS criteria was compared to an estimate of the total number of at-risk patients treated at participating sites and, following weighting, was extrapolated to 5520 US rheumatology practices. US census data were used to estimate national prevalence.

Results.

In a sample of 816 randomly selected records, 514 (63%) at-risk patients (95% confidence interval 59.6–66.3%) met ASAS criteria. By applying this proportion to 1,217,097 Americans estimated at risk, 766,652 were projected to meet ASAS criteria. This projection corresponds to a national prevalence of 0.70% (0.38–1.1%), or 701 per 100,000 individuals. The prevalence estimates of AS and nonradiographic axial SpA are 0.35% (0.18–0.554%) and 0.35% (0.18–0.554%), respectively. Rheumatologists diagnosed axial SpA in 491 (60%) of those at-risk, corresponding to 0.67%(0.36–1.01%) prevalence overall. However, of 514 patients meeting ASAS criteria, 124 (24%) were undiagnosed by rheumatologists.

Conclusion.

This is the first systematic epidemiology study of axial SpA using ASAS criteria. Better recognition of axial symptoms is needed, as rheumatologists' expert clinical diagnosesare not always in agreement with ASAS criteria. © 2013 by the American College of Rheumatology

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