In patients with early spondyloarthritis (SpA), disagreement in the detection of erosions on pelvic radiograph may drive the limited reproducibility of sacroiliac joint (SIJ) radiograph classification, according to a study published in The Journal of Rheumatology.

“The limited reproducibility of radiographic SIJ classification according to the modified New York criteria (mNY) in early SpA is well documented,” Alice Christiansen, MD, of the University of Southern Denmark, told Rheumatology Advisor. Several studies have shown that disagreement between readers of SIJ radiographs may lead to reclassification of over one-third of patients with nonradiographic axial SpA.1,2

“Although magnetic resonance imaging (MRI) is increasingly used in SpA diagnostics and may displace conventional radiography in the future, many clinicians still have to rely on pelvic radiographs,” Dr Christiansen said.


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Dr Christiansen and colleagues evaluated the reproducibility of radiographic SIJ classification and potential drivers of disagreement in patients with possible axial SpA.3

A total of 104 patients were enrolled, previously recruited into the Spines of Southern Denmark cohort, who had positive SIJ MRI by Assessment of SpondyloArthritis International Society (ASAS) criteria or were human leukocyte antigen (HLA)-B27-positive with ≥1 clinical or laboratory SpA feature per the ASAS classification criteria for axial SpA. Pelvic radiographs were classified according to the mNY criteria by 2 musculoskeletal radiologists and 5 rheumatologists.3

The concordance (κ value) among all 7 readers was moderate at 0.39, which was somewhat lower than the previously reported concordance of 0.54 in a similar population.3,4 The concordance between the most experienced rheumatologist and each of the 2 musculoskeletal radiologists was 0.55 and 0.36, respectively.3

Among 21 reader pairs, disagreement in mNY classification existed for approximately 16% of patients. Of the 5 radiographic lesions types assessed, erosion had the lowest interreader agreement, with concordance in only 25% of mNY-discrepant patients.3

Summary and Clinical Applicability 

Radiographic SIJ evaluation according to the mNY criteria is often used to classify patients with axial SpA, but its reproducibility is limited. The study authors examined the reproducibility of radiographic SIJ classification and potential drivers of disagreement in a SpA inception cohort.

“Our study suggests that the key to understanding limited reproducibility may be disagreement in the detection of erosion,” Dr Christiansen concluded. “This may be due to the fact that the mNY criteria used for classification do not come with clear definitions of the lesions under investigation.”

“Clinicians should be aware of the limitations of pelvic radiography when assessing low back pain in patients with features suggestive of axial SpA, as patients can easily be misclassified as having or not having axial SpA, respectively,” she added.

Limitations and Disclosures

·         The majority of SIJ radiographs were pelvic radiographs obtained with the anteroposterior view, while the remainder were obtained with oblique SIJ views or were lumbar spine radiographs. These differences in radiographic views may have impacted reproducibility.

·         In contrast to the rheumatologists, the musculoskeletal radiologists did not undergo full reader calibration, which may have affected reproducibility.

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References 

  1. U.S. Food and Drug Administration, Department of Health & Human Services. Arthritis Advisory Committee Meeting: sBLA 125057/323: adalimumab for the treatment of active nonradiographic axial spondyloarthritis in adults with objective signs of inflammation by elevated C-reactive protein (CRP) or magnetic resonance imaging (MRI), who have had an inadequate response to, or are intolerant to, a nonsteroidal anti-inflammatory drug. www.fda.gov/downloads/AdvisoryCommittees/CommitteesMeetingMaterials/Drugs/ArthritisAdvisoryCommittee/UCM361563.pdf. Published July 23, 2013. Accessed November 7, 2016.

  2. U.S. Food and Drug Administration, Department of Health & Human Services. Arthritis Advisory Committee Meeting: sBLA 125160/215: Cimzia (certolizumab) for the treatment of active axial spondyloarthritis, including patients with ankylosing spondylitis. www.fda.gov/downloads/AdvisoryCommittees/CommitteesMeetingMaterials/Drugs/ArthritisAdvisoryCommittee/UCM361565.pdf. Published July 23, 2013. Accessed November 7, 2016.

  3. Christiansen AA, Hendricks O, Kuettel D, et al. Limited Reliability of Radiographic Assessment of Sacroiliac Joints in Patients with Suspected Early Spondyloarthritis. J Rheumatol. Published online: Oct 15, 2016.

  4. van den Berg R, Lenczner G, Feydy A, et al. Agreement between clinical practice and trained central reading in reading of sacroiliac joints on plain pelvic radiographs. Results from the DESIR cohort. Arthritis Rheumatol. 2014;66:2403-11.

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