Researchers published findings in Arthritis & Rheumatology on September 28 detailing how a blood test measuring five specific proteins could detect individuals with ankylosing spondylitis (AS) experiencing significant structural joint deterioration.
The test demonstrated strong accuracy, correctly identifying patients with advanced ankylosing spondylitis damage at a rate reflected by an area under the curve (AUC) of 0.917.
Analysis of the protein data highlighted platelet function, blood clotting mechanisms, and extracellular matrix remodeling as key biological processes contributing to structural harm—indicating damage extends beyond general inflammation alone.
While such blood-based biomarkers could enhance current imaging techniques for evaluating joint destruction, experts emphasize additional verification is required before widespread clinical adoption.
Understanding Ankylosing Spondylitis and Structural Degradation
The condition ankylosing spondylitis represents a persistent inflammatory joint disorder primarily targeting the spine and sacroiliac regions, often resulting in irreversible structural changes and abnormal bone growth over time.
Current evaluations of ankylosing spondylitis-related structural damage rely on X-rays and MRI scans, supplemented by scoring systems like the SPARCC (Spondyloarthritis Research Consortium of Canada) assessment.
However, Binita Sapkota, MD, a Cleveland Clinic rheumatologist, points out that imaging alone presents notable challenges in detecting early or progressive damage.
Challenges in Diagnosing Axial Spondyloarthritis Through Imaging
According to Dr. Sapkota, a primary drawback of imaging techniques is their delayed ability to capture evolving structural changes in axial spondyloarthritis.
While MRI excels at visualizing inflammation, it falls short in precisely identifying bony structural alterations, she noted.
For instance, bone marrow edema visible on MRI lacks specificity and may appear in individuals with degenerative conditions, postpartum recovery, athletes, or even healthy people.
Although CT scans offer better visualization of bone changes, they carry radiation exposure risks. Even then, Dr. Sapkota observed that CT may still miss early structural modifications.
Protein Analysis Reveals New Pathways in Structural Damage
Though inflammation drives ankylosing spondylitis, standard inflammatory markers often fail to predict the severity of structural deterioration or abnormal bone formation.
To explore underlying molecular mechanisms, investigators performed full plasma protein profiling on 88 participants diagnosed with ankylosing spondylitis.
The study group included 25 individuals with severe structural damage, 31 with minimal damage, and 32 healthy controls for comparison.
This analysis uncovered 536 proteins that differed significantly between those with advanced damage and healthy individuals.
A Five-Protein Test for Early Damage Detection
Using LASSO (Least Absolute Shrinkage and Selection Operator) regression, the team initially pinpointed 28 proteins with potential as biomarkers for high structural damage.
Further machine learning techniques narrowed the field to five key proteins: ITGA2B, HSPG2, ITGB1, EPHB2, and SAA2.
When evaluated across all 88 participants, each of these proteins showed statistically significant differences between groups.
Individually, their diagnostic performance ranged from AUC values of 0.732 to 0.819 in distinguishing patients with severe damage. However, when combined into a single model, the five-protein panel achieved an AUC of 0.917, suggesting substantially improved detection capabilities.
This combined approach may help clinicians assess AS-related structural harm by capturing both inflammatory activity and tissue remodeling processes, according to the study authors.
Sean Carter, MD, a rheumatologist at the Medical University of South Carolina, suggested that such blood biomarkers could address gaps in imaging by revealing structural changes that scans might overlook. He added they might also forecast the likelihood of future joint deterioration.
Both Dr. Sapkota and Dr. Carter stressed that larger studies are essential to determine which patient populations would benefit most from this five-protein screening method before it can be integrated into routine care.
The research team is now refining the panel to enhance its precision in predicting structural progression in ankylosing spondylitis patients.
