Researchers published findings in Arthritis & Rheumatology on September 28 detailing how a blood test measuring five specific proteins could detect significant structural damage in adults with ankylosing spondylitis (AS). The panel demonstrated strong accuracy, achieving an area under the curve (AUC) score of 0.917 when identifying patients with advanced joint deterioration.
Ankylosing spondylitis represents a persistent inflammatory arthritis predominantly targeting the spine and sacroiliac joints, resulting in progressive structural changes and abnormal bone growth. Current evaluations rely on X-rays, MRI scans, and scoring systems like the Spondyloarthritis Research Consortium of Canada (SPARCC) score to quantify damage.
Challenges of Relying on Imaging Alone
Current diagnostic imaging methods face significant drawbacks in monitoring AS progression, according to Binita Sapkota, MD, a Cleveland Clinic rheumatologist. She explains that imaging techniques often fail to capture early-stage inflammation or bone remodeling before irreversible damage occurs. “The main limitation of imaging in axial spondyloarthritis is delay in capturing the changes,” she said.
While MRI provides superior inflammation detection, its usefulness for assessing bony damage remains limited. Dr. Sapkota points out that bone marrow edema visible on MRI lacks specificity, appearing in conditions ranging from normal postpartum recovery to athletic adaptations in healthy individuals. Computed tomography offers better bony detail but introduces radiation exposure and still may not identify structural changes until they become well-established.
Protein Analysis Reveals New Damage-Related Pathways
To explore the biological mechanisms driving structural damage, scientists analyzed plasma samples from 88 AS patients in a prospective study. The group included 25 individuals with severe damage, 31 with minimal damage, and 32 healthy controls.
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The proteomic screening uncovered 536 proteins that differed significantly between those with severe damage and healthy participants. Among patients with advanced structural changes, raised protein levels were particularly associated with platelet function, blood clotting processes, and interactions between cells and the extracellular matrix. These findings suggest that damage progression involves complex mechanisms beyond general inflammation.
Dr. Sapkota emphasizes the critical need for improved biomarkers, noting that existing inflammatory markers provide incomplete information about disease severity. There is substantial need for better biomarkers to identify extensive structural damage in AS, she said.
Five-Protein Test Shows Clinical Potential
Using statistical modeling techniques, researchers initially narrowed down 28 candidate proteins before identifying five with particular promise: ITGA2B, HSPG2, ITGB1, EPHB2, and SAA2. When evaluated across the study cohort, each protein showed significant differences between damage groups, with individual AUC values ranging from 0.732 to 0.819.
However, when combined into a single panel, these biomarkers achieved a substantially higher AUC of 0.917, indicating enhanced diagnostic capability.