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First Steps Toward Improving Care for Children with Axial Disease and Juvenile Spondyloarthritis
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By Timothy Brandon, MPH and Pamela F. Weiss, MD, MSCE

Classification Criteria for Axial Disease in Youth with Juvenile Spondyloarthritis

Intro:

Axial disease in youth is a difficult to treat and often underdiagnosed condition affecting the spine and sacroiliac joints. This form of arthritis can cause pain and stiffness in the back and is sometimes mistaken for other conditions. Axial disease is a characteristic component frequently occurring in a group of conditions known as juvenile spondyloarthritis (SpA), the most common form of juvenile arthritis across the world accounting for as much as one-third of all cases. When untreated, these children are at risk of progression to ankylosing spondylitis which can result in fusion of the joints, functional impairment, and psychological impact that lasts into adulthood.

A major obstacle to advancing the care of children with SpA and axial disease is an absence of clinical trials despite an increasing number of potential therapies being approved in adults. Clinical trials cannot be conducted without valid, comprehensive, and easy-to-use disease classification criteria for this population.

Criteria for the classification of axial spondyloarthritis in adults was developed in 2009, but axial SpA presents differently in juveniles than it does in adults. Separate criteria for the pediatric population have been needed. The criteria proposed by the authors have similarities to the adult criteria with important distinctions adapted for the juvenile population.

Study design & findings:

The criteria were created through a rigorous four-phase process involving international experts:

  • Item Generation: A thorough review of the medical literature and feedback from 199 physicians produced a list of 108 potential criteria items.
  • Item Selection: Experts narrowed this list down to 37 key items.
  • Criteria Development: SpA experts assessed patients leading to the selection of seven key domains, with data-driven levels of importance assigned within each.
  • Validation: The criteria were tested with data from real patients and an independent team of experts to ensure they work as intended.

The criteria focus on seven domains that reflect key features of AxJSpA:

  1. Evidence of active inflammation on MRI
  2. Structural lesions on MRI (or radiograph if MRI is unavailable)
  3. Pain chronicity (how long pain has lasted and how frequently it occurs)
  4. Pain pattern (onset of pain and how it responds to treatment/activity)
  5. Pain location
  6. Morning stiffness
  7. Genetics (family history, HLA-B27 status)

The most heavily weighted factors are imaging evidence of inflammation and structural damage, but no single feature alone is enough to classify someone with AxJSpA.  

To meet the criteria, a patient must score at least 55 out of 100 points based on these factors. At least some imaging evidence is necessary, but not sufficient to meet the classification threshold. Importantly, a physician's diagnosis of juvenile SpA is a required starting point for using the criteria. 

AxJSpA. classification criteria

Research in Practice Implications:

These new expert-designed criteria provide researchers with a reliable way to study AxJSpA, but they don’t change how the condition is diagnosed or treated in everyday practice. They ensure that clinical studies include patients who truly have AxJSpA, which improves the quality of research and will help develop better treatments. 

Actionable Insights:  

Clinical: It’s important to remember that these criteria are not a diagnostic tool. Only a doctor can diagnose AxJSpA after considering a patient’s full medical history, symptoms, and test results.

Research: These definitions have been validated and are ready to be used as eligibility criteria for clinical trials. Visit the AxJSpA Classification Criteria Calculator to calculate an AxJSpA score. 

Clinical Futures author(s): Pamela F. Weiss, Timothy G. Brandon

Citation: 
Weiss PF, Brandon TG, Aggarwal A, Burgos-Vargas R, Colbert RA, Horneff G, Laxer RM, Minden K, Ravelli A, Ruperto N, Smith JA, Stoll ML, Tse SM, Van den Bosch F, Maksymowych WP, Lambert RG, Biko DM, Chauvin NA, Francavilla ML, Jaremko JL, Herregods N, Kasapcopur O, Yildiz M, Srinivasalu H, Lovell DJ, Nigrovic PA, Foeldvari I, Klein-Gitelman MS, Ozen S, Naden R, Hendry AM, Joos R. Classification Criteria for Axial Disease in Youth With Juvenile Spondyloarthritis. Arthritis Rheumatol. 2024 Dec;76(12):1797-1808. doi: 10.1002/art.42959. Epub 2024 Sep 8. PMID: 39039899; PMCID: PMC11606790.