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Misdiagnosing and Overdiagnosing AxSpA: An ‘Imaging Crisis?'
TORONTO — MRI is central to the early detection and diagnosis of axial spondyloarthritis (axSpA), but years-long diagnostic delays are still common.
However, experts are warning that misinterpretation of MRI findings is contributing to significant increases in false-positive diagnoses in patients presenting with back pain that may be caused by other, noninflammatory conditions.
The good news is that studies show that diagnostic accuracy in the interpretation of MRI findings can be significantly improved when rheumatologists provide radiologists with all the clinical information relevant to a diagnosis of axSpA.
'There is a high risk of misdiagnosis and overdiagnosis of axSpA in clinical practice,' said Denis Poddubnyy, MD, PhD, professor in the Division of Rheumatology, Temerty Faculty of Medicine at the University of Toronto, Toronto, Ontario, Canada.
Denis Poddubnyy, MD, PhD
'In 2025, evidence of SpA-compatible active inflammatory and structural changes on MRI of the sacroiliac joints is needed for a diagnosis of axSpA,' he said in a presentation at the Spondyloarthritis Research and Treatment Network (SPARTAN) 2025 Annual Meeting. 'There's been a paradigm shift.'
Evidence for this paradigm shift comes from the ongoing Improve-axSpA project, Poddubnyy said. The telemedicine initiative, which involves rheumatologists and orthopedists at 40 centers across Germany and Austria, is focused on enhancing the diagnosis of axSpA.
Interim findings showed that clinicians misinterpreted the MRI findings in 35% of 476 cases of suspected axSpA submitted for central evaluation.
These cases could be explained by noninflammatory conditions that mimic the symptoms of axSpA, said the investigators, led by Poddubnyy. These axSpA-like conditions include degenerative or mechanical changes in the sacroiliac joint (SIJ), degenerative disk disease, and osteitis condensans ilii — a mechanical condition that is often associated with bone marrow edema in the SIJs.
'I believe this [35%] figure is very accurate, not only for Europe — or Germany and Austria — but for anywhere that physicians are trying to apply MRI findings to make an early diagnosis,' Poddubnyy told Medscape Medical News .
This finding could also account for a significant proportion of the 40%-50% of patients with axSpA who don't respond to treatment, he said.
In the study, central evaluation ruled out axSpA in a whopping 75% of the 183 cases with an inconclusive local diagnosis. In the other 25% of these cases, the diagnosis could not be confirmed by central assessment because of insufficient imaging.
This disturbing trend provides evidence of an 'imaging crisis' in axSpA, said Torsten Diekhoff, MD, PhD, a radiologist and associate professor, Charité — Universitätsmedizin Berlin, Berlin, Germany, in an editorial published on May 16, 2025, in The Lancet Rheumatology . Poddubnyy was a co-author.
'The prevailing dilemma in imaging of axial spondyloarthritis lies in the incongruence between early detection and the confidence of the imaging assessment,' they wrote. 'Although clinical work-around strategies have been developed to address this issue, they frequently fail to resolve the fundamental concern of achieving an early diagnosis before the manifestation of structural lesions.'
When asked to comment, Jonathan Chan, MD, clinical associate professor, University of British Columbia, Vancouver, British Columbia, Canada, said there are 'definitely some major changes that we all agree are important.' One of them is acknowledging that MRI is a better tool than x-ray and that there is heavier weighting for MRI than for x-ray.
'We know that structural lesions are important, and we know that sometimes bone marrow edema can be intermittent, whereas the presence of multiple erosions will not reverse. That is something you can hang your hat on.'
The consequences of diagnostic delay in patients with axSpA are well known and include less favorable treatment response and worse clinical outcomes.
In 2019, an analysis of health insurance data in Germany from 1677 patients with axSpA revealed that diagnostic delay was common, with a mean of 5.7 years. The factors associated with longer time to diagnosis included female gender, negative HLA-B27 status, the presence of psoriasis, and a younger age at symptom onset.
In its 2022 update of management recommendations for axSpA, members of the Assessment of Spondyloarthritis International Society (ASAS)-European Alliance of Associations for Rheumatology (EULAR) task force addressed the importance of ruling out alternative explanations for symptoms to avoid unnecessary treatment changes.
The diagnostic accuracy of MRI imaging interpreted by physicians in clinical practice could be improved with expert support from a telemedicine platform that 'transcends borders,' said Poddubnyy, who is also a clinician investigator at the Schroeder Arthritis Institute, University Health Network, Toronto, Ontario, Canada.
'We want to diagnose patients early, but we need to be extremely careful about how we interpret the imaging of the sacroiliac joints and the spine,' he emphasized.
What to Do When MRI Availability Is Limited
For many clinicians, however, x-rays are the diagnostic imaging go-to, particularly in areas where access to MRI is limited.
'The specificity of x-rays is not great,' Poddubnyy said. 'If you have to perform x-rays first in your clinical setting, that's okay, but be extremely critical in terms of interpreting this imaging. If you have any doubts about whether axial disease is present, order a cross-sectional image.'
When MRI is not readily available, CT may be a good alternative, he suggested. In the Improve-axSpA study, for instance, CT had higher specificity and produced fewer false-positive results than MRI. CT also captured more specific lesions, including erosions and ankylosis.
Sharing clinical information can vastly improve MRI interpretation, a 2024 study showed. The results demonstrated that when rheumatologists gave radiologists essential clinical information relevant to the diagnosis of axSpA — not just patient age and gender — the precision and specificity of imaging interpretation significantly improved.
When clinical information was available along with conventional radiographs, the precision of SIJ radiograph interpretation — meaning the percentage agreement between diagnosis by a rheumatologist and the radiology report confirming or excluding a diagnosis of axSpA — jumped from 70% to 78%.
This kind of information-sharing doesn't happen routinely in clinical practice, said the investigators, led by Tim Pohlner, Charité — Universitätsmedizin Berlin.
Some clinicians think that sharing essential clinical information will cause bias on the part of the radiologist, explained Poddubnyy.
The expertise of both rheumatologists and radiologists is needed to diagnose axSpA, he added, and that means all information on clinical and imaging outcomes must be accessible.
'This is something that should be done in daily clinical practice, in every radiology setting,' Poddubnyy emphasized. 'Rheumatologists should be initiating this, bringing the radiologist to this idea.'
The 2024 ASAS recommendations on clinical information to include on imaging referrals provide support for differentiating inflammatory from noninflammatory changes in patients with suspected or known axSpA.
A downloadable checklist that can be shared with the radiologist includes information such as patient history, back pain characteristics, HLA-B27 status, physical activity level, pregnancy history, and SpA parameters.
For Chan, who is also a clinical investigator at Arthritis Research Canada, Vancouver, British Columbia, Canada, the importance of sharing clinical information became evident while he was working on the CLASSIC study to revise classification criteria for axSpA in adults.
'We would meet every five scans and do a calibration with two or three central reader radiologists and then our local reader radiologist, who was using the 2009 [ASAS] classification criteria. After…our local reader realized what he was missing and what he needed to look for, it was very easy for him to' change the way he practiced.
When asked to comment, Walter P. Maksymowych, MBChB, professor of medicine at the University of Alberta, Edmonton, Alberta, Canada, agreed that sharing clinical information such as HLA-B27 status is important. However, he emphasized that classification criteria for axSpA should not be used to diagnose the disease in clinical practice.
Walter P. Maksymowych, MBCh
'These criteria are aimed at identifying patients with shared clinical characteristics for the purposes of clinical research, especially clinical trials research,' he said. 'I do think they help highlight key lessons,' he added, 'particularly the importance of MRI as a diagnostic tool.'
Education to Improve Diagnostic Accuracy
Education of both rheumatologists and radiologists is needed to improve diagnostic accuracy in axSpA, Poddubnyy said in a recent commentary in Nature Reviews Rheumatology .
'Rheumatologists need appropriate training to recognize the potential imaging pitfalls when diagnosing axSpA,' wrote Poddubnyy and Xenofon Baraliakos, MD, PhD, head of Rheumatology at the Rheumazentrum Ruhrgebiet, in Herne, Germany. Baraliakos is also president-elect of EULAR and past president of ASAS.
'Radiologists require specialized knowledge in interpreting MRI (as well as other imaging) findings in the sacroiliac joints and spine and guidance on how to differentiate inflammatory from mechanical or degenerative changes,' they wrote.
Looking ahead, Poddubnyy and Baraliakos noted the emergence of artificial intelligence (AI) and AI-assisted tools in the imaging arena. Early evidence shows that AI can detect subtle patterns of inflammation and structural damage and could potentially increase the accuracy of interpreting axSpA-specific changes.
Molecular imaging of inflammatory molecules using modalities such as PET could also prove valuable for determining whether bone marrow edema is related to axSpA or to mechanical stress or degenerative changes.
In the meantime, the ASAS interactive online case library is an important resource for both rheumatologists and radiologists, Poddubnyy and Baraliakos said. It provides clinical cases with imaging that represent the entire spectrum of axSpA and the most common differential diagnoses.
Other resources include the 2024 international ASAS-SPARTAN standardized image acquisition protocol for diagnostic evaluation of the SIJs by MRI and the 2024 international ASAS recommendations for reporting SIJ imaging, which detail ways in which alternative diagnoses can be considered.
Online tools, training, and continuing medical education programs are also available at CARE Arthritis Ltd., said Maksymowych, who is chief medical officer.
'We have instructions on how MRI imaging should be performed and how it should be interpreted, with an extensive library of MRI scans in a DICOM [Digital Imaging and Communications in Medicine] format. We also provide other tools for clinicians, such as how to assess enthesitis, do a physical exam, and so on.'
When all is said and done, early diagnosis increases the likelihood of a good treatment response.
'The earlier, the better,' Poddubnyy said.
Studies of patients with symptoms of 3-5 years' duration have demonstrated the highest response rates, including remission, he pointed out.
'I'm pretty much convinced that early diagnosis and early treatment, and achieving an early inflammation-free and symptom-free state, will decrease the likelihood of chronic pain and the development of fibromyalgia,' Poddubnyy said.
'And with early and appropriate control of inflammation, we should be able to prevent the progression of structural damage, especially in the spine, and avoid long-term disability caused by ankylosis.'
