Findings reinforce the value of imaging for AxPsA
The presence of HLA-B27 may predict the radiographic phenotype of patients with axial spondyloarthritis (axSpA), according to recent research.
Dr. Laura C. Coates
The findings suggest HLA-B27-positive patients have worse radiographic damage, more typical marginal syndesmophytes, and a greater number of bilateral fused sacroiliac joints in the spine, reported Laura C. Coates, MBChB, PhD, of the University of Oxford (England) and colleagues. Their report was published in Arthritis Care & Research.
“In order to achieve phenotypic diversity, we studied patients with PsA [psoriatic arthritis] and axial involvement (a group of patients recognized to have less frequent carriage of HLA-B27), and AS [ankylosing spondylitis],” they wrote.
The researchers conducted a multicenter, cross-sectional cohort study involving 198 patients with AS and 244 with PsA. Various clinical, radiographic, and laboratory data were collected from databases in Ireland, Spain, Germany, Russia, Canada, and Italy.
HLA-B27-positive patients were older (mean 49.1 years vs. 53.8 years), were more often male (73% vs. 59%), and had longer disease duration (mean 13.6 years vs. 11.0 years).
The team compared HLA-B27 carriers and noncarriers on syndesmophyte morphology, the symmetry of the sacroiliac joints and syndesmophytes, in addition to radiographic damage, as measured by the modified Stoke Ankylosing spondylitis spinal score (mSASSS) and PsA Spondylitis Radiology Index (PASRI).
After analysis, the researchers found that HLA-B27 positivity was associated with higher median mSASSS (6 vs. 2; P = .04) and PASRI scores (12 vs. 6; P less than .0001), marginal syndesmophytes (odds ratio, 1.97; 95% confidence interval, 1.16-3.36), and syndesmophyte symmetry (OR, 3.02; 95% CI, 1.38-6.61).
“[Our] study [showed] no difference in sacroiliac symmetry, and no difference in nonmarginal syndesmophytes, according to HLA-B27 status,” they reported.
In addition, they reported that male sex (OR, 1.66; 95% CI, 1.04-2.66) and age (OR, 1.08; 95% CI, 1.05-1.10) were positive predictors of marginal syndesmophytes.
In contrast, only male sex (OR, 2.55; 95% CI, 1.46-4.64) and age (OR, 1.05; 95% CI, 1.03-1.07) predicted the presence of nonmarginal syndesmophytes.
The researchers acknowledged that two key limitations of the study were the absence of disease-group matching and lack of independent central reading of radiographs.
“This analysis suggests less difference in radiographic phenotype between AS and axial PsA than previously found but emphasizes the importance of HLA-B27 status in severity and the phenotypic expression of disease radiographically,” they concluded.
The study was funded by the Academy of Medical Sciences (U.K.). The authors reported having no conflicts of interest.
SOURCE: Coates LC et al. Arthritis Care Res. 2020 Feb 26. doi: 10.1002/acr.24174.