Background The antiphospholipid syndrome (APS) and systemic lupus erythematosus (SLE) are known to be associated with increased risk of cardiovascular disease (CVD). However, there are few data regarding the osteoprotegerin (OPG), one of the validated markers of the CVD risk, in patients with APS or SLE.
Objectives The aim of this study was to evaluate the correlations between the OPG and antiphospholipid antibodies (APLA).
Methods Patients with APS (primary and secondary to SLE) were successively included. The diagnosis was sustained according to the 2006 Sydney APS's criteria, respectively to the 2012 SLICC SLE's criteria. Laboratory workup included the “diagnostic” APLA [IgG and IgM anticardiolipin (aCL), IgG and IgM anti-β2 glycoprotein I (aβ2GPI)] and also the “non-diagnostic” APLA [IgG and IgM antiphosphatidylserine (aPS), IgG and IgM anti phosphatidylethanolamine (aPE), respectively IgG and IgM antiprothrombin (aPT)]. We assessed the SCORE and Framingham risk as the widely used score of CVD risk in general population. We divided the study group in two subgroups: A - patients with low OPG (≤1.5 pg/ml), and B - patients with high OPG (>1.5 pg/ml).
Results For the 40 patients included, the mean age at inclusion (SD) was 43.7±10.7 years. OPG values were higher in patients with history of stroke vs patients without stroke (3.44±2.24 vs 2.15±1.5, p=0.02). We did not found differences of OPG values in patients with or without history of stable angina, myocardial infarction or peripheral artery disease. Values of SCORE risk (1.19±1.81 vs 0.43±0.75, p=0.03) and Framingham risk (6.56±6.41 vs 3.9±2.73, p=0.02) were significantly higher in group B comparing with group A. Moreover, in patients associating SLE, the SLEDAI score was higher in group B vs group A (4.47±3.51 vs 4.00±6.21, p=0.04). Also, for the SLE patients, we found a higher prevalence for the anti-DNA and anti-Sm in patients with high OPG (2/5 vs 13/0; p=0.042, respectively 0/7 vs 6/7; p=0.032). OPG values were positively correlates only with the values of IgM aPT (0.35, p=0.02). When we performed the ROC curve analysis, we found that the titers of IgM aPT, IgG aβ2GPI, and IgG aPE were the best predictors of an OPG values>1.5 [AUC (CI) 0.604 (0.418-0.791), 0.578 (0.392-0.795), respectively 0.536 (0.342-0.730)]. For the patients with APS secondary to SLE, IgM aPT and IgG aPE [AUC (CI) 0.632 (0.348-0.915), respectively 0.549 (0.289-0.810)] were the best predictors of high OPG levels.
Conclusions OPG levels might be related with CVD risk in patients with APS. The OPG levels were correlated with “non-diagnostic” APLA, raising the hypothesis of “non-diagnostic” APLA involvement in the pathogenesis of CVD risk in patients with APS. Moreover, the anti-DNA and anti-Sm might be to be related with the OPG levels in patients with APS secondary to SLE. This is an interesting finding especially as we do not have yet a clear explanation for the increased CVD risk in SLE.
Acknowledgements This paper is supported by the POSDRU/159/1.5/S/137390.
Disclosure of Interest None declared
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