Background/Purpose:  Due to the limitation of early diagnosis of ankylosing spondylitis (AS), updated criteria in recent years introduced the concept of axial spondyloarthritis (axSpA) and non- radiographic axial spondyloarthritis (nr-axSpA) and facilitates classification management of disease. It has been controversial whether the two sub-phenotypes are separate or different phases of radiographic progression. Studies has revealed calprotectin as inflammation marker and the Wnt/β-catenin pathway contributed to the bone fusion in AS.

Methods: We enrolled 53 patients with AS, 59 patients with nr-axSpA and 47 healthy individuals. Patients were diagnosed with AS or nr-axSpA according to the modified New York criteria or ASAS classification criteria for axSpA. Laboratory tests including ESR, CRP and human leukocyte antigen (HLA)-B27 were conducted. Bath Ankylosing Spondylitis Disease Activity Index (BASDAI), Bath Ankylosing Spondylitis Functional Index (BASFI) and Ankylosing Spondylitis Disease Activity Score (ASDAS) were evaluated. Imaging assessment was calculated using Spondyloarthritis Research Consortium Canada (SPARCC) scoring system for sacroiliac joints and modified Stoke’s Ankylosing Spondylitis Spine Score. Serum levels of calprotectin, GSK-β,β-catenin, RUNX2 were determined by commercial ELISA kit. Data were described as mean and SD. Mann–Whitney U test or Kruskal–Wallis test was used to compare continuous variables. Correlations were assessed using the Spearman’s rank correlation coefficient. Statistical analyses were performed with SPSS V.13.0 software. A p value <0.05 was considered statistically significant.

Results:  Clinical characteristics and laboratory results were described in Table 1. Serum calprotectin level was higher in AS and nr-axSpA patients than that in healthy individuals. No difference was observed in calprotectin level between AS and nr-axSpA patients. Elevated calprotectin was positively correlated with ESR, CRP, BASDAI, ASDAS as well as SPARCC scoring and had no correlation with BASFI and mSASSS in these two sub-genotypes. No correlation was observed between calprotectin and Wnt/β-catenin pathway markers. Radiographic progression indicated by mSASSS was correlated merely with disease duration instead of other outcome measurements.

Conclusion:  Calprotectin does not contribute to the discrimination of AS and nr-axSpA. Patients with nr-axSpA are not necessarily progress to AS. Calprotectin mediated inflammation was not correlated with principle effectors of Wnt/β-catenin pathway, indicating inflammation and bone fusion might be separate process of the disease . Long-term follow-up favors further investigation of value of inflammation subsequent bone information. Table 1 Clinical characteristics and laboratory results in AS and nr-axSpA patients

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/discriminating-value-of-calprotectin-in-disease-activity-and-progression-of-non-radiographic-axial-spondyloarthritis-and-ankylosing-spondylitis/