Background/Purpose:  Calprotectin is a protein involved in several cellular processes including immunomodulation¹. Elevated levels of this protein have been observed in inflammatory diseases, since it is secreted into inflamed tissues during monocyte infiltration². Osteoprotegerin (OPG), a member of the tumor necrosis factor receptor superfamily, has been associated with increased risk and severity of atherosclerotic disease³. Both molecules have been proposed as potential biomarkers of atherosclerosis^4,5. In contrast to ankylosing spondylitis (AS), non radiographic axial spondyloarthritis (nr-axSpA) patients do not seem to develop early atherosclerotic disease⁶. Due to this, we aimed to compare calprotectin and OPG levels in AS and nr-axSpA and to assess the potential involvement of both molecules as biomarkers of subclinical atherosclerosis in both types of SpA.

Methods:  Serum calprotectin and OPG levels were measured by ELISA in 202 Spanish patients diagnosed with axSpA recruited from Hospital Universitario Marqués de Valdecilla and Hospital de Laredo (Spain). axSpA patients fulfilled the Assessment of SpondyloArthritis international Society (ASAS) classification criteria⁷. Of them, 53 fulfilled the definitions for nr-axSpA⁷, while 149 also fulfilled definitions for AS according to the 1984 modified New York criteria⁸. Patients with previous history of cardiovascular (CV) disease were excluded. All the patients underwent a carotid ultrasound study to assess the presence of abnormal carotid intima-media thickness (cIMT) and presence of plaques (both surrogate markers of CV disease), as previously described⁹. Differences in calprotectin and OPG levels among the study groups were assessed by Mann-Whitney test. Correlations of these molecules with surrogate markers of CV disease were studied. The association with cIMT values was assessed by linear regression, while the association with plaques was tested by logistic regression. All the results were adjusted by potential confounder factors. Statistical analysis was performed using STATA® v. 11.1.

Results:  nr-axSpA and AS patients displayed similar levels of serum calprotectin and OPG. When the potential association between calprotectin and OPG levels and cIMT values or presence of plaques was assessed, no statistically significant results were obtained, neither in the axSpA cohort nor in the two subgroups of AS and nr-axSpA patients (p>0.05 for all comparisons).

Conclusion: Our results do not confirm an association between calprotectin and OPG levels with subclinical atherosclerosis in our cohort of Spanish axSpA patients. [1] Arterioscler Thromb Vasc Biol 2015;35(12):2496-2507; [2] Ann Rheum Dis 2014;73:1746–8; [3] J Rheumatol 2014;41(3):429-36; [4] Arthritis Rheumatol 2015;67(10); [5] Clin Exp Rheumatol 2014;32(5):640-6; [6] Clin Exp Rheumatol 2016;34(1):159-60; [7] Ann Rheum Dis 2009;68:777-83; [8] Arthritis Rheum 1984;27:361-368; [9] Clin Exp Rheumatol 2015;33(3):315-320 FG is a recipient of a Sara Borrell postdoctoral fellowship from the Instituto de Salud Carlos III at the Spanish Ministry of Health (Spain)(CD15/00095). RLM and BU are supported by funds from the RETICS Program (RIER)(RD12/0009/0013) (Spain).

ACR Meeting Abstracts - https://acrabstracts.org/abstract/assessment-of-serum-calprotectin-and-osteoprotegerin-levels-in-a-cohort-of-spanish-patients-with-axial-spondyloarthritis/