Background: Magnetic resonance imaging (MRI) plays a central role in diagnosing, classifying, and monitoring axial spondyloarthritis (axSpA). Since the introduction of the ASAS classification criteria in 2009, a definition of a positive MRI for sacroiliac joints (SIJ) has been used worldwide, with a separate definition for the spine introduced later. Over the years, new evidence from international studies, including the CLASSIC study, has highlighted the need to refine these definitions to improve diagnostic accuracy and to differentiate true axSpA-related changes from false-positive findings seen in non-axSpA individuals.

The ASAS MRI working group has led this effort for over a decade, providing standardized descriptions of inflammatory and structural lesions. However, these definitions have not been systematically updated since their initial publication, despite major advances in imaging and clinical research.

This project aims to produce revised, consensus-based definitions of a positive MRI of the SIJ and spine, integrating both inflammatory and structural lesions to ensure accurate classification and improved specificity in clinical studies and practice.

Aim: To reach international expert consensus on updated definitions for active inflammatory and structural MRI lesions of the SIJ and spine required to define a positive MRI for axSpA classification. Representative case examples will be developed to guide clinicians and researchers, including examples of false-positive findings.

Methodology:

The project will be conducted by the ASAS MRI working group in five key steps:

1. Formation of steering committee and working group

   • A steering committee (SC) of five members and a working group (WG) including two Young-ASAS members and two patient representatives has been established.

   • The draft protocol is developed.

2. Systematic literature review (SLR)

   • Two fellows will review all published literature on SIJ and spinal MRI lesions.

   • Findings will be discussed and key data selected for further analysis.

3. Delphi consensus survey

4. Consensus presentation at ASAS meeting

   • Final definitions will be presented to the ASAS community for discussion, voting, and endorsement.

5. Validation on external cohort

   • The new definitions is planned to be be validated using established cohorts

Timelines of the project: 2025-2026

Project Team

Principal Investigators (PIs):

• Xenofon Baraliakos (Germany)

• Denis Poddubnyy (Canada)

Steering Committee:

• Xenofon Baraliakos (Germany)
• Torsten Diekhoff (Germany)
• Iris Eshed (Israel)
• Pedro Machado (United Kingdom)
• Denis Poddubnyy (Canada)

Task Force / Working Group:

• Sibel Aydin (Canada)
• Wilson Bautista-Molano (Colombia)
• Paul Bird (Australia)
• Praveena Chiowchanwisawakit (Thailand)
• Rodrigo García Salinas (Argentina)
• Floris van Gaalen (Netherlands)
• Kay-Geert Hermann (Germany)
• Nele Herregods (Belgium)
• Manouk de Hooge (Belgium)
• Mariana Ivanova (Bulgaria)
• Lennart Jans (Belgium)
• Jacob Jaremko (Canada)
• Nikolaos Kougkas (Greece)
• Robert B.M. Landewé (Netherlands)
• Robert Lambert (Canada)
• Walter Maksymowych (Canada)
• Ashish Jacob Mathew (India)
• Helena Marzo-Ortega (United Kingdom)
• Victoria Navarro Compán (Spain)
• Sofia Ramiro (Netherlands)
• Monique Reijnierse (Netherlands)
• Martin Rudwaleit (Germany)
• Raj Sengupta (United Kingdom)
• Mikkel Østergaard (Denmark)
• Susanne Juhl Pedersen (Denmark)
• Ulrich Weber (Switzerland)

Fellows (Y-ASAS):

• Bhowmik Meghnathi (India)
• Mikhail Protopopov (Germany)

Patient Representative:

• Andri Phoka