Article Text
Abstract
Objective The variety of disease phenotypes among patients with SLE challenges the identification of new biomarkers reflecting disease activity and/or organ damage. Osteopontin (OPN) is an extracellular matrix protein with immunomodulating properties. Although raised levels have been reported, the pathogenic implications and clinical utility of OPN as a biomarker in SLE are far from clear. Thus, the aim of this study was to characterise OPN in SLE.
Methods Sera from 240 well-characterised adult SLE cases classified according to the American College of Rheumatology (ACR) and/or the Systemic Lupus International Collaborating Clinics (SLICC) criteria, and 240 population-based controls were immunoassayed for OPN. The SLE Disease Activity Index 2000 (SLEDAI-2K) was used to evaluate disease activity and the SLICC/ACR Damage Index (SDI) to detect damage accrual.
Results Serum OPN levels were in average raised fourfold in SLE cases compared with the controls (p<0.0001). OPN correlated with SLEDAI-2K, especially in patients with a disease duration of <12 months (r=0.666, p=0.028). OPN was highly associated with SDI (p<0.0001), especially in the renal (p<0.0001), cardiovascular (p<0.0001) and malignancy (p=0.012) domains. Finally, OPN associated with coherent antiphospholipid syndrome (APS; p=0.009), and both clinical and laboratory criteria of APS had significant positive impact on OPN levels.
Conclusions In this cross-sectional study, circulating OPN correlates with disease activity in recent-onset SLE, reflects global organ damage and associates with APS. Longitudinal studies to dissect whether serum OPN also precedes and predicts future organ damage are most warranted.
- systemic lupus erythematosus
- antiphospholipid syndrome
- organ damage
- disease activity
- biomarker
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Footnotes
Contributors LW performed the OPN ELISA, contributed to study design, statistical analysis, interpretation of data and manuscript writing. MF contributed to APS data and manuscript drafting. HE contributed to interpretation of data and manuscript drafting. TS contributed to the original idea and study design, interpretation of data and manuscript writing. JW contributed to the original idea and study design, interpretation of data and manuscript writing. CS contributed to the original idea and study design, patient characterisation, interpretation of data and manuscript writing.
Competing interests None declared.
Patient consent Obtained.
Ethics approval The Regional Ethics Review Board in Linköping, Sweden. Decision No. M75-08/2008.
Provenance and peer review Not commissioned; externally peer reviewed.
Data sharing statement No additional data available.