title: Predictive validity of the ASAS classification criteria for axial and peripheral spondyloarthritis after follow-up in the ASAS cohort: a final analysis.
abstract: OBJECTIVE
  To establish the predictive validity of the Assessment of SpondyloArthritis international Society (ASAS) spondyloarthritis (SpA) classification criteria.
  
  
  METHODS
  22 centres (N=909 patients) from the initial 29 ASAS centres (N=975) participated in the ASAS-cohort follow-up study. Patients had either chronic (>3 months) back pain of unknown origin and age of onset below 45 years (N=658) or peripheral arthritis and/or enthesitis and/or dactylitis (N=251). At follow-up, information was obtained at a clinic visit or by telephone. The positive predictive value (PPV) of the baseline classification by the ASAS criteria was calculated using rheumatologist's diagnosis at follow-up as external standard.
  
  
  RESULTS
  In total, 564 patients were assessed at follow-up (345 visits; 219 telephone) with a mean follow-up of 4.4 years (range: 1.9; 6.8) and 70.2% received a SpA diagnosis by the rheumatologist. 335 patients fulfilled the axial SpA (axSpA) or peripheral SpA (pSpA) criteria at baseline and of these, 309 were diagnosed SpA after follow-up (PPV SpA criteria: 92.2%). The PPV of the axSpA and pSpA criteria was 93.3% and 89.5%, respectively. The PPV for the 'clinical arm only' was 88.0% and for the 'clinical arm'±'imaging arm' 96.0%, for the 'imaging arm only' 86.2% and for the 'imaging arm'+/-'clinical arm' 94.7%. A series of sensitivity analyses yielded similar results (range: 85.1-98.2%).
  
  
  CONCLUSIONS
  The PPV of the axSpA and pSpA criteria to forecast an expert's diagnosis of 'SpA' after more than 4 years is excellent. The 'imaging arm' and 'clinical arm' of the axSpA criteria have similar predictive validity and are truly complementary.
authors: Department of Rheumatology, Leiden University Medical Center, Leiden, The Netherlands Department of Rheumatology, Hospital de Egas Moniz-CHLO, Lisbon, Portugal.
authors: Alexandre
authors: A
authors: Sepriano
authors: Departments of Clinical Immunology & Rheumatology, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands Department of Rheumatology, Atrium Medical Center, Heerlen, The Netherlands.
authors: Robert
authors: R
authors: Landewé
authors: Department of Rheumatology, Leiden University Medical Center, Leiden, The Netherlands.
authors: Désirée
authors: http://orcid.org/0000-0002-5781-158X
authors: D
authors: van der Heijde
authors: Department of Rheumatology, Med Klinik I, Charité Campus Benjamin Franklin, Berlin, Germany German Rheumatism Research Centre, Berlin, Germany.
authors: Joachim
authors: J
authors: Sieper
authors: Department of Rheumatology, Faculty of Medicine, Dokuz Eylul University, Izmir, Turkey.
authors: Nurullah
authors: N
authors: Akkoc
authors: Department of Rheumatology, Private Practice, Berlin, Germany.
authors: Jan
authors: J
authors: Brandt
authors: Rheumazentrum Ruhrgebiet, Herne, Germany.
authors: Jürgen
authors: J
authors: Braun
authors: Rheumatology Department, "Reina Sofia" Hospital/IMIBIC/University of Córdoba, Córdoba, Spain.
authors: Eduardo
authors: E
authors: Collantes-Estevez
authors: Rheumatology Department, Paris Descartes University, Cochin Hospital, Paris, France.
authors: Maxime
authors: M
authors: Dougados
authors: Department of Rheumatology, St Vincent's University Hospital, Dublin, Elm Park, Ireland.
authors: Oliver
authors: O
authors: Fitzgerald
authors: Department of Rheumatology, Chinese PLA General Hospital, Beijing, China.
authors: Feng
authors: F
authors: Huang
authors: Department of Rheumatology, Third Affiliated Hospital of Sun Yat-sen University, Guangzhou, China.
authors: Jieruo
authors: J
authors: Gu
authors: Department of Physical Medicine and Rehabilitation, Medical Faculty of Ege University, Izmir, Turkey.
authors: Yesim
authors: Y
authors: Kirazli
authors: Department of Medicine, University of Alberta, Edmonton, Alberta, Canada.
authors: Walter P
authors: WP
authors: Maksymowych
authors: Leeds Institute of Rheumatic and Musculoskeletal Medicine, Chapel Allerton Hospital, University of Leeds, Leeds, UK.
authors: Helena
authors: H
authors: Marzo-Ortega
authors: Rheumatology Department of Lucania, San Carlo Hospital of Potenza and Madonna delle Grazie Hospital of Matera, Potenza, Italy.
authors: Ignazio
authors: I
authors: Olivieri
authors: Division of Rheumatology, Department of Physical Medicine and Rehabilitation, Erciyes University, School of Medicine, Gevher Nesibe Hospital, Kayseri, Turkey.
authors: Salih
authors: S
authors: Ozgocmen
authors: Department of Rheumatology and Rehabilitation, King George's Hospital, London, UK.
authors: Euthalia
authors: E
authors: Roussou
authors: Rheumatology Unit, M. Scarlato Hospital, Scafati, Salerno, Italy.
authors: Salvatore
authors: S
authors: Scarpato
authors: Copenhagen Center for Arthritis Research, Center for Rheumatology and Spine Diseases, Glostrup Hospital, Glostrup, Denmark Department of Clinical Medicine, University of Copenhagen, Copenhagen, Denmark.
authors: Inge J
authors: IJ
authors: Sørensen
authors: Division of Rheumatology, Department of Internal Medicine, Hospital Militar Central, Bogotá, Colombia.
authors: Rafael
authors: R
authors: Valle-Oñate
authors: Department of Rheumatology, Ghent University Hospital, Ghent, Belgium.
authors: Filip
authors: F
authors: Van den Bosch
authors: Department of Rheumatology, VU University Medical Centre, Amsterdam, Netherlands.
authors: Irene
authors: I
authors: van der Horst-Bruinsma
authors: King Christian 10th Hospital for Rheumatic Diseases, Gråsten, and South Jutland Hospital, Denmark Institute of Regional Health Research, University of Southern Denmark, Odense, Denmark.
authors: Ulrich
authors: U
authors: Weber
authors: Chung Shan Medical University Hospital, Taichung, Taiwan.
authors: James
authors: J
authors: Wei
authors: Klinikum Bielefeld, Berlin, Germany Charité University Medicine, Berlin, Germany.
authors: Martin
authors: M
authors: Rudwaleit
mesh_terms: D000328:Adult; D017668:Age of Onset; D001368:Axis, Cervical Vertebra; D001416:Back Pain / Q000175:diagnosis* / Q000209:etiology; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D011446:Prospective Studies; D015203:Reproducibility of Results; D025241:Spondylarthritis / Q000150:complications / Q000175:diagnosis*
keywords: Epidemiology; Outcomes research; Spondyloarthritis