The Assessments in Spondyloarthritis International Society (ASAS) and Spondyloarthritis Research and Treatment Network (SPARTAN) Revised Classification Criteria for Axial Spondyloarthritis: Development and Validation in the Classification of Axial SpA Inception Cohort Study

Walter P. Maksymowych¹, Désirée van der Heijde², Liron Caplan³, Robert Landewé⁴, Lianne S. Gensler⁵, Pedro Machado⁶, Alexandre Sepriano⁷, Floris A. van Gaalen², Miranda van Lunteren², Ben Vandermeer⁸, Servet Akar⁹, Sibel Aydin¹⁰, Xenofon Barliakos¹¹, Wilson bautista molano¹², Stephanie Bernard¹³, RUBEN BURGOS-VARGAS¹⁴, John Carrino¹⁵, Alberto Cauli¹⁶, Jonathan Chan¹⁷, Abhijeet Danve¹⁸, Torsten Diekhoff¹⁹, Maxime Dougados²⁰, iris Eshed²¹, Warren Fong²², Rodrigo García Salinas²³, Hildrun Haibel²⁴, Nigil Haroon²⁵, Kay-Geert Hermann²⁶, Lennart Jans²⁷, Anne Jurik²⁸, Uta Kiltz²⁹, Tae-Jong Kim³⁰, Robert G. W. Lambert³¹, Clementina López Medina³², Ennio Lubrano³³, Marina Magrey³⁴, Vikas Majithia³⁵, Helena Marzo-Ortega³⁶, Philip J. Mease³⁷, Victoria Navarro-Compan³⁸, John O'Neill³⁹, Mikkel Ostergaard⁴⁰, Salih Ozgocmen⁴¹, Susanne Pedersen⁴², Fernando Pimentel-Santos⁴³, Denis Poddubnyy⁴⁴, Fabian Proft⁴⁵, Sofia Ramiro⁴⁶, Monique Reijnierse⁴⁷ and John Reveille⁴⁸, ¹Department of Medicine, University of Alberta, ⁵⁶⁸ Heritage Building, Edmonton, AB, Canada, ²Department of Rheumatology, Leiden University Medical Center, Leiden, Netherlands, ³Medicine Service, Rocky Mountain Regional VAMC, Aurora, CO, ⁴Department of Rheumatology, Amsterdam University Medical Center, Amsterdam, Netherlands; and Zuyderland Medical Center, Heerlen, Netherlands, ⁵Department of Medicine/Rheumatology, University of California, San Francisco, San Francisco, CA, ⁶Department of Rheumatology, University College London, and Department of Rheumatology, Northwick Park Hospital, London North West University Healthcare NHS Trust, Centre for Rheumatology & Department of Neuromuscular Diseases, University College London, London, United Kingdom, ⁷Department of Rheumatology, Leiden University Medical Centre, Portela Loures, Portugal, ⁸Department of Medicine, University of Alberta, Edmonton, AB, Canada, ⁹Department of Medicine, Izmir Katip Çelebi University School of Medicine, Izmir, Turkey, ¹⁰Department of Medicine, University of Ottawa, The Ottawa Hospital Research Institute, Ottawa, ON, Canada, ¹¹Ruhr-University Bochum, Rheumazentrum Ruhrgebiet, Herne, Germany, ¹²University Hospital Fundacion Santa Fe de Bogota, Bogota, Colombia, ¹³Department of Radiology, Brooke Army Medical Center, Fort Sam Houston, TX, ¹⁴Department of Rheumatology, Hospital General de Mexico, Faculty of Medicine, Universidad Nacional Autonoma de Mexico, Ciudad de México, Mexico, ¹⁵Department of Radiology and Imaging, Hospital for Special Surgery, New York, NY, ¹⁶Rheumatology Unit, Department of Medicine and Public Health, AOU and University of Cagliari, Cagliari, Italy, ¹⁷Department of Medicine, University of British Columbia, Vancouver, BC, Canada, ¹⁸Section of Rheumatology, Department of Medicine, Yale School of Medicine, New Haven, CT, ¹⁹Department of Radiology, Immanuel Clinic Ruedersdorf, Brandenburg Medical School, Ruedersdorf, Germany, ²⁰Department of Medicine, Hopital Cochin, Universite de Paris, Paris, France, ²¹Department of Diagnostic Imaging, Sheba Medical Center, Tel Hashomer affiliated with School of Medicine, Tel Aviv University, Tel Aviv, Israel, ²²Department of Medicine, Singapore General Hospital, Singapore, Singapore, ²³Hospital Italiano La Plata, La Plata, Argentina, ²⁴Charite- University Medicine Berlin Campus Benjamin Franklin, Berlin, Germany, ²⁵Department of Medicine/Rheumatology, University Health Network, Schroeder Arthritis Institute, University of Toronto, Toronto, ON, Canada, ²⁶Department of Radiology, Charité – Universitätsmedizin Berlin, Berlin, Germany, ²⁷Department of Radiology, Ghent University Hospital, Ghent, Belgium, ²⁸Department of Radiology, Aarhus University Hospital, Aarhus, Denmark, ²⁹Rheumazentrum Ruhrgebiet Herne, Ruhr-University Bochum, Herne, Germany, ³⁰Department of Medicine, Chonnam National University Hospital, Seoul, Republic of Korea, ³¹University of Alberta, Department of Radiology & Diagnostic Imaging, Edmonton, AB, Canada, ³²Department of Medicine, Hospital Universitario Reina Sofia, University of Cordoba, IMIBIC, Cordoba, Spain, ³³Department of Medicine, Università deglia Studi del Molise, CAMPOBASSO, Italy, ³⁴Case Western Reserve University School of Medicine/University Hospitals Cleveland, Richfield, OH, ³⁵Mayo Clinic Hospital, Jacksonville, FL, ³⁶NIHR Leeds Biomedical Research Centre, The Leeds Teaching Hospitals NHS Trust and Leeds Institute of Rheumatic and Musculoskeletal Medicine (LIRMM), University of Leeds, Leeds, United Kingdom, ³⁷Department of Rheumatology, Providence-Swedish Medical Center and University of Washington, Seattle, WA, ³⁸Department of Rheumatology, La Paz University Hospital, IdiPaz, Madrid, Spain, ³⁹Department of Radiology, McMaster University, Hamilton, ON, Canada, ⁴⁰Department of Clinical Medicine, University of Copenhagen, Copenhagen, Denmark, and Copenhagen Center for Arthritis Research, Center for Rheumatology, Rigshospitalet, Glostrup, Denmark, ⁴¹Department of Rheumatology, Istinye University/Faculty of Medicine, Istanbul, Turkey, ⁴²Department of Medicine, Rigshopital, University of Copenhagen, Copenhagen, Denmark, ⁴³NOVA Medical School, Universidade NOVA e Lisboa, Lisboa, Portugal, ⁴⁴Division of Rheumatology, Department of Medicine, University Health Network and University of Toronto, Toronto, Ontario, Canada, and Department of Gastroenterology, Infectious Diseases and Rheumatology, Charité – Universitätsmedizin Berlin, Berlin, Germany; Department of Epidemiology, German Rheumatism Research Centre, Berlin, Germany, ⁴⁵Department of Gastroenterology, Infectiology and Rheumatology (including Nutrition Medicine), Charité – Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Berlin, Germany, ⁴⁶Leiden University Medical Center, Bunde, Netherlands, ⁴⁷Department of Radiology, Leiden University Medical Center, Leiden, Netherlands, ⁴⁸Department of Medicine, University of Texas Medical Center, Houston, TX

Meeting: ACR Convergence 2025

Keywords: Ankylosing spondylitis (AS), classification criteria, spondyloarthritis

Session Information

Date: Monday, October 27, 2025

Title: Plenary II (0849–0854)

Session Type: Plenary Session

Session Time: 9:15AM-9:30AM

Background/Purpose: The 2009 ASAS classification criteria had sensitivity (Sn) of 83% and specificity (Sp) of 84% for a rheumatologist diagnosis of axial spondyloarthritis (axSpA). Given the high prevalence of back pain, greater specificity would be desirable. The global Classification in Axial Spondyloarthritis Inception Cohort (CLASSIC) study was established as a combined initiative of ASAS and SPARTAN to validate the performance of the 2009 criteria according to prespecified Sn/Sp targets of ≥75%/≥90%.

Methods: CLASSIC recruited consecutive patients referred to a rheumatologist with current undiagnosed back pain of ≥3 months duration with onset ≤45 years of age. Diagnostic evaluations for axSpA were performed at 5 stages: Stage 5 provided all diagnostic information including centralized imaging review by two primary readers and an adjudicator, and served as reference standard. The cohort data were randomly divided into testing and validation datasets (50:50). The testing dataset was used to develop candidate criteria, while the validation dataset evaluated whether criteria achieved the Sn/Sp targets, using the stage 5 global diagnosis as the reference standard. Regression techniques (least absolute shrinkage and selection operator (LASSO), multivariable logistic regression (MLR)) were used to identify which SpA variables were independently associated with stage 5 diagnosis and for estimating the strength of this association according to LASSO coefficients. Final selection of SpA variables and their weighting was determined by expert consensus and the final proposal was selected by a vote of the combined ASAS and SPARTAN membership.

Results: CLASSIC included 1015 patients from 61 centers in 27 countries of whom 370 (36.5%) were diagnosed with axSpA per stage 5 global. The 2009 ASAS classification criteria did not meet the prespecified targets (Sn 82.4%, Sp 77.1%)1, indicating the need for revised criteria. MRI of the SIJ indicative of axSpA by global assessment of both active and structural lesions had the highest independent association with stage 5 diagnosis of axSpA followed by radiographic sacroiliitis. Selected clinical variables were HLA-B27, inflammatory back pain, inflammatory bowel disease, acute anterior uveitis, heel enthesitis, and dactylitis. Expert consensus led to the inclusion of psoriasis and replacement of dactylitis by elevated CRP. Two high-performing proposals in the testing dataset achieved the Sn/Sp targets in the validation dataset (Figures 1 and 2). The final proposal selected by the ASAS-SPARTAN vote (158 vs 151, 9 abstained) assigned weights for the selected SpA variables based on LASSO coefficients and achieved Sn of 79.5% and Sp of 90.4% in the validation dataset (Table).

Conclusion: The ASAS-SPARTAN revised classification criteria for axSpA achieved prespecified performance targets of ≥75% sensitivity and ≥90% specificity, emphasizing the central role of imaging and incorporating a more focused set of clinical variables compared to the 2009 ASAS criteria.< !1. Maksymowych et al. Arthritis Rheumatol 2024;76 (suppl 9):0820

Figure 1. ASAS-SPARTAN revised classification criteria for axial spondyloarthritis in A. Tree, and B. Table, formats.

Figure 2. Rejected alternative proposal for axial spondyloarthritis classification criteria in A. Tree, and B. Table, formats.

Table. Sensitivity and specificity of A. ASAS-SPARTAN revised classification criteria, and B. Rejected proposal, for final rheumatologist diagnosis of axial spondyloarthritis

Disclosures: W. Maksymowych: AbbVie, 2, 5, 6, BMS, 2, 5, 6, Boehringer-Ingelheim, 2, Celgene, 2, Chief Medical Officer for CARE ARTHRITIS, 4, Eli Lilly, 2, 5, 6, Galapagos, 2, 5, 6, Janssen, 2, 6, Novartis, 2, 5, 6, Pfizer, 2, 5, 6, UCB, 2, 5, 6; D. van der Heijde: AbbVie/Abbott, 2, Alfasigma, 2, ArgenX, 2, Bristol-Myers Squibb(BMS), 2, Eli-Lilly, 2, Grey-Wolf Therapeutics, 2, Imaging Rheumatology BV, 4, Janssen, 2, Novartis, 2, Pfizer, 2, Takeda, 2, UCB Pharma, 2; L. Caplan: None; R. Landewé: AbbVie/Abbott, 2, Bristol-Myers Squibb(BMS), 2, Eli Lilly, 2, Janssen, 2, Joint Imaging BV, 12, Director, Novartis, 2, Pfizer, 2, Rheumatology Consultancy BV, 12, Director, UCB, 2; L. Gensler: Acelyrin, 2, Eli Lilly, 2, Janssen, 2, Novartis, 2, Pfizer, 2, UCB, 2, 5; P. Machado: AbbVie/Abbott, 2, 6, Eli Lilly, 2, 6, Novartis, 2, 6, Pfizer, 2, 6, UCB, 2, 6; A. Sepriano: AbbVie/Abbott, 2, 6, Eli Lilly, 2, 6, UCB, 2, 6; F. van Gaalen: AbbVie, 2, BMS, 2, Eli Lilly, 2, Jacobus Stichting, 5, MSD, 2, Novartis, 2, 5, Stichting ASAS, 5, Stichting vrienden van Sole Mio, 5, UCB, 5; M. van Lunteren: None; B. Vandermeer: None; S. Akar: None; S. Aydin: AbbVie/Abbott, 5, 6, Eli Lilly, 5, 6, Janssen, 5, 6, Novartis, 5, 6, Pfizer, 5, 6, UCB, 5, 6; X. Barliakos: Abbvie, 1, 2, 5, Advanz, 1, 2, Alexion, 1, 2, Alfasigma, 1, 2, Amgen, 1, 2, Astra Zeneca, 1, 2, Bristol-Myers Squibb(BMS), 1, 2, Celltrion, 1, 2, 5, Cesas, 1, 2, Clarivate, 1, 2, Eli-Lilly, 1, 2, Galapagos, 1, 2, Janssen, 5, Johnson and Johnspn, 1, 2, Moonlake, 1, 2, 5, Novartis, 1, 2, 5, Peervoice, 1, 2, Pfizer, 1, 2, Roche, 1, 2, Sandoz, 1, 2, Springer, 1, 2, Stada, 1, 2, Takeda, 1, 2, UCB Pharma, 1, 2, Zuellig, 1, 2; W. bautista molano: None; S. Bernard: None; R. BURGOS-VARGAS: None; J. Carrino: Arthritis & Rheumatology, 12, Editorial Board, Carestream, 4, Cartilage Imaging, 12, Editorial Board, Covera, 2, Image Analysis Group, 4, Image Biopsy Lab, 4, Radiology, 12, Editorial Board; A. Cauli: None; J. Chan: Abbvie, 2, 6, Celltrion, 2, 6, Eli-Lilly, 2, 6, Fresenius, 2, 6, Janssen, 2, 6, Novartis, 2, 6, Organon, 2, 6, UCB Pharma, 2, 6; A. Danve: AbbVie, 2, Amgen, 2, Eli Lilly, 5, Janssen, 2, Novartis, 2, 5; T. Diekhoff: Abbvie, 1, 6, Berlin Flame, 1, 6, Bracco, 2, 6, Canon MS, 2, 6, Eli-Lilly, 1, 2, 6, Janssen, 2, 6, Merck/MSD, 2, 6, Novartis, 2, 6, UCB Pharma, 1, 2, 6; M. Dougados: None; i. Eshed: None; W. Fong: None; R. García Salinas: AbbVie/Abbott, 2, 5, 6, Adium, 2, 5, 6, Amgen, 2, 5, 6, Biogen, 2, 5, 6, Bristol-Myers Squibb(BMS), 2, 5, 6, Eli Lilly, 2, 5, 6, GlaxoSmithKlein(GSK), 2, 5, 6, Janssen, 2, 5, 6, Novartis, 2, 5, 6, Pfizer, 2, 5, 6, Raffo, 2, 5, 6, Roche, 2, 5, 6, UCB, 2, 5, 6; H. Haibel: Abbvie, 2, 6, Alfasigma, 5, GlaxoSmithKlein(GSK), 6, Janssen, 2, 6, Novartis, 2, 5, 6, Pfizer, 2, 5, Sobi, 5, 6, UCB Pharma, 2, 5, 6; N. Haroon: AbbVie, 2, Eli Lilly, 2, Janssen, 2, UCB, 2; K. Hermann: None; L. Jans: Abbvie, 6, Alfasigma, 6, Eli-Lilly, 6, Janssen, 6, Novartis, 6, UCB Pharma, 6; A. Jurik: None; U. Kiltz: AbbVie, 2, 5, Amgen, 2, 5, Biocad, 2, 5, Biogen, 2, 5, BMS, 2, 5, Chugai, 2, 5, Eli Lilly, 2, 5, Fresenius, 2, 5, Gilead, 2, 5, Grünenthal, 2, 5, GSK, 2, 5, Hexal, 2, 5, Janssen, 2, 5, MSD, 2, 5, Novartis, 2, 5, onkowissen.de, 2, 5, Pfizer, 2, 5, Roche, 2, 5, UCB, 2, 5, Viatris, 2, 5; T. Kim: None; R. Lambert: AbbVie, 2, CARE Arthritis and Image Analysis Group, 2; C. López Medina: None; E. Lubrano: AbbVie, 6, Amgen, 6, Eli Lilly, 6, GlaxoSmithKlein, 6, Johnson & Johnson, 6, Novartis, 6, UCB, 6; M. Magrey: AbbVie, 2, 5, Amgen, 5, BMS, 2, 5, Eli Lilly, 2, Novartis, 2, Pfizer, 2, UCB, 2, 5; V. Majithia: None; H. Marzo-Ortega: AbbVie, 2, 6, Amgen, 2, 6, Biogen, 2, 6, Eli Lilly, 2, 6, Janssen, 2, 5, 6, MoonLake Immunotherapeutics, 2, 6, Novartis, 2, 5, 6, Pfizer, 2, 5, 6, Takeda, 2, 6, UCB, 2, 5, 6; P. Mease: AbbVie, 2, 5, 6, Acelyrin, 2, 5, Amgen, 2, 5, 6, BMS, 2, 5, Century, 2, Cullinan, 2, Eli Lilly and Company, 2, 5, 6, Inmagene, 2, J&J Innovative Medicine, 2, 5, 6, MoonLake Immunotherapeutics, 2, Novartis, 2, 5, 6, Pfizer, 2, 5, 6, Sana, 5, Spyre, 5, Takeda, 2, UCB, 2, 5, 6; V. Navarro-Compan: AbbVie, 2, 5, 6, Alfasigma, 2, Bristol Myers Squibb, 2, 5, 6, Fresenius Kabi, 2, 5, 6, Galapagos, 2, 5, 6, Janssen, 2, 5, 6, Lilly, 2, 5, 6, MoonLake, 2, 5, 6, MSD, 2, 5, 6, Novartis, 2, 5, 6, Pfizer, 2, 5, 6, Roche, 2, 5, 6, UCB, 2, 5, 6; J. O'Neill: None; M. Ostergaard: AbbVie, 2, 5, 6, Amgen, 5, BMS, 2, 5, 6, Celgene, 2, 5, 6, Eli Lilly, 2, 5, 6, Galapagos, 2, 6, Gilead, 2, 6, Janssen, 2, 6, MEDAC, 6, Merck, 2, 5, 6, Novartis, 2, 5, 6, Pfizer, 2, 6, Sandoz, 6, UCB, 2, 5, 6; S. Ozgocmen: None; S. Pedersen: None; F. Pimentel-Santos: None; D. Poddubnyy: AbbVie, 2, 5, 6, Biocad, 2, BMS, 6, Eli Lilly, 2, 5, 6, Gilead, 2, GSK, 2, Moonlake, 2, MSD, 2, 5, 6, Novartis, 2, 5, 6, Pfizer, 2, 5, 6, Samsung Bioepis, 6, UCB, 2, 6; F. Proft: AbbVie, 2, 6, Amgen, 2, 6, BMS, 2, 6, Celgene, 2, 6, Eli Lilly and Company, 2, 5, 6, Galapagos, 2, 6, Hexal, 2, 6, Janssen, 2, 6, Medscape, 2, 6, MoonLake Pharma, 2, 6, MSD, 2, 6, Novartis, 2, 5, 6, Pfizer, 2, 6, Roche, 2, 6, UCB, 2, 5, 6; S. Ramiro: AbbVie, 2, 5, Eli Lilly, 2, 5, Galapagos/Alfasigma, 2, 5, Janssen, 2, MSD, 2, 5, Novartis, 2, 5, Pfizer, 2, 5, Sanofi, 2, 5, UCB, 2, 5; M. Reijnierse: None; J. Reveille: Surf Therapeutics, 5.

To cite this abstract in AMA style:

Maksymowych W, van der Heijde D, Caplan L, Landewé R, Gensler L, Machado P, Sepriano A, van Gaalen F, van Lunteren M, Vandermeer B, Akar S, Aydin S, Barliakos X, bautista molano W, Bernard S, BURGOS-VARGAS R, Carrino J, Cauli A, Chan J, Danve A, Diekhoff T, Dougados M, Eshed i, Fong W, García Salinas R, Haibel H, Haroon N, Hermann K, Jans L, Jurik A, Kiltz U, Kim T, Lambert R, López Medina C, Lubrano E, Magrey M, Majithia V, Marzo-Ortega H, Mease P, Navarro-Compan V, O'Neill J, Ostergaard M, Ozgocmen S, Pedersen S, Pimentel-Santos F, Poddubnyy D, Proft F, Ramiro S, Reijnierse M, Reveille J. The Assessments in Spondyloarthritis International Society (ASAS) and Spondyloarthritis Research and Treatment Network (SPARTAN) Revised Classification Criteria for Axial Spondyloarthritis: Development and Validation in the Classification of Axial SpA Inception Cohort Study [abstract]. Arthritis Rheumatol. 2025; 77 (suppl 9). https://acrabstracts.org/abstract/the-assessments-in-spondyloarthritis-international-society-asas-and-spondyloarthritis-research-and-treatment-network-spartan-revised-classification-criteria-for-axial-spondyloarthritis-developmen/. Accessed .

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