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Which definitions for MRI sacroiliac joint lesions predict the diagnosis of early axial spondyloarthritis best? : A 2-year follow-up in the SPACE cohort

de Bruin, Liese J E ; Marques, Mary Lucy ; van Lunteren, Miranda ; de Hooge, Manouk ; Reijnierse, Monique ; Exarchou, Sofia LU ; Berg, Inger Jorid ; Ramonda, Roberta ; Landewé, Robert and van Gaalen, Floris A , et al. (2026) In RMD Open 12(1).
Abstract

BACKGROUND: The Leiden group and the Assessment of Spondyloarthritis International Society (ASAS)-MRI study group have proposed definitions for structural (SL) and active (AL) lesions typical for axial spondyloarthritis (axSpA) on MRI of the sacroiliac joints (MRI-SIJ).

OBJECTIVES: To analyse the predictive validity of proposed SL and AL MRI-SIJ definitions in early axSpA and compare proposed AL with the current ASAS-MRI-SIJ+ definition.

METHODS: Patients with chronic back pain (≤2 years) from the Spondyloarthritis Caught Early cohort were diagnosed as axSpA or non-axSpA after 2 years follow-up. Three central readers scored baseline MRI-SIJ for SL (erosions and fat lesions) and AL (bone marrow oedema). Validation required... (More)

BACKGROUND: The Leiden group and the Assessment of Spondyloarthritis International Society (ASAS)-MRI study group have proposed definitions for structural (SL) and active (AL) lesions typical for axial spondyloarthritis (axSpA) on MRI of the sacroiliac joints (MRI-SIJ).

OBJECTIVES: To analyse the predictive validity of proposed SL and AL MRI-SIJ definitions in early axSpA and compare proposed AL with the current ASAS-MRI-SIJ+ definition.

METHODS: Patients with chronic back pain (≤2 years) from the Spondyloarthritis Caught Early cohort were diagnosed as axSpA or non-axSpA after 2 years follow-up. Three central readers scored baseline MRI-SIJ for SL (erosions and fat lesions) and AL (bone marrow oedema). Validation required specificity and positive predictive value (PPV) ≥95%.

RESULTS: Among 643 patients (52% axSpA), SL were infrequent (2%-14%). All Leiden and most MRI study group SL definitions met the validation threshold, except for 'erosion in ≥2 consecutive slices' and the overall MRI study group definition (PPV <95%). The ASAS-MRI-SIJ+ definition had a higher sensitivity than the MRI study group AL (40% vs 31%) with similar specificity (98% vs 99%). Combining SL and AL, the Leiden SL with ASAS-MRI-SIJ+ definition met the validation threshold with the highest sensitivity (46%). SL increased sensitivity beyond AL alone by 6%-11%.

CONCLUSIONS: The ASAS-MRI-SIJ+ definition outperforms the MRI study group AL. The Leiden SL combined with the ASAS-MRI-SIJ+ definition is validated, most sensitive and feasible as it simultaneously upholds lesion quantification and detection precision, making it the preferred approach. Nevertheless, SL were uncommon in early axSpA, contributing only marginally beyond AL definitions in early diagnosis.

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publishing date
type
Contribution to journal
publication status
published
subject
keywords
Humans, Sacroiliac Joint/diagnostic imaging, Magnetic Resonance Imaging/methods, Male, Female, Adult, Axial Spondyloarthritis/diagnosis, Follow-Up Studies, Middle Aged, Predictive Value of Tests, Sensitivity and Specificity
in
RMD Open
volume
12
issue
1
article number
e006425
publisher
BMJ Publishing Group
external identifiers
  • pmid:41802832
ISSN
2056-5933
DOI
10.1136/rmdopen-2025-006425
language
English
LU publication?
yes
additional info
© Author(s) (or their employer(s)) 2026. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ Group.
id
99748a5f-9eb8-480b-a1de-cf188e145882
date added to LUP
2026-03-10 08:10:48
date last changed
2026-03-10 10:56:02
@article{99748a5f-9eb8-480b-a1de-cf188e145882,
  abstract     = {{<p>BACKGROUND: The Leiden group and the Assessment of Spondyloarthritis International Society (ASAS)-MRI study group have proposed definitions for structural (SL) and active (AL) lesions typical for axial spondyloarthritis (axSpA) on MRI of the sacroiliac joints (MRI-SIJ).</p><p>OBJECTIVES: To analyse the predictive validity of proposed SL and AL MRI-SIJ definitions in early axSpA and compare proposed AL with the current ASAS-MRI-SIJ+ definition.</p><p>METHODS: Patients with chronic back pain (≤2 years) from the Spondyloarthritis Caught Early cohort were diagnosed as axSpA or non-axSpA after 2 years follow-up. Three central readers scored baseline MRI-SIJ for SL (erosions and fat lesions) and AL (bone marrow oedema). Validation required specificity and positive predictive value (PPV) ≥95%.</p><p>RESULTS: Among 643 patients (52% axSpA), SL were infrequent (2%-14%). All Leiden and most MRI study group SL definitions met the validation threshold, except for 'erosion in ≥2 consecutive slices' and the overall MRI study group definition (PPV &lt;95%). The ASAS-MRI-SIJ+ definition had a higher sensitivity than the MRI study group AL (40% vs 31%) with similar specificity (98% vs 99%). Combining SL and AL, the Leiden SL with ASAS-MRI-SIJ+ definition met the validation threshold with the highest sensitivity (46%). SL increased sensitivity beyond AL alone by 6%-11%.</p><p>CONCLUSIONS: The ASAS-MRI-SIJ+ definition outperforms the MRI study group AL. The Leiden SL combined with the ASAS-MRI-SIJ+ definition is validated, most sensitive and feasible as it simultaneously upholds lesion quantification and detection precision, making it the preferred approach. Nevertheless, SL were uncommon in early axSpA, contributing only marginally beyond AL definitions in early diagnosis.</p>}},
  author       = {{de Bruin, Liese J E and Marques, Mary Lucy and van Lunteren, Miranda and de Hooge, Manouk and Reijnierse, Monique and Exarchou, Sofia and Berg, Inger Jorid and Ramonda, Roberta and Landewé, Robert and van Gaalen, Floris A and van der Heijde, Désirée and Ramiro, Sofia}},
  issn         = {{2056-5933}},
  keywords     = {{Humans; Sacroiliac Joint/diagnostic imaging; Magnetic Resonance Imaging/methods; Male; Female; Adult; Axial Spondyloarthritis/diagnosis; Follow-Up Studies; Middle Aged; Predictive Value of Tests; Sensitivity and Specificity}},
  language     = {{eng}},
  month        = {{03}},
  number       = {{1}},
  publisher    = {{BMJ Publishing Group}},
  series       = {{RMD Open}},
  title        = {{Which definitions for MRI sacroiliac joint lesions predict the diagnosis of early axial spondyloarthritis best? : A 2-year follow-up in the SPACE cohort}},
  url          = {{http://dx.doi.org/10.1136/rmdopen-2025-006425}},
  doi          = {{10.1136/rmdopen-2025-006425}},
  volume       = {{12}},
  year         = {{2026}},
}