Objective This study aimed to systemically review the evidence regarding the relationship between circulating blood osteopontin (OPN) level and systemic lupus erythematosus (SLE), correlation between serum OPN levels and SLE activity, and association between OPN polymorphisms and SLE susceptibility. Methods We conducted a meta-analysis on the serum/plasma OPN levels in SLE patients and healthy controls, correlation coefficients between the circulating OPN level and SLE Disease Activity Index (SLEDAI) in SLE patients, and the association between OPN polymorphisms and SLE risk. Results Nine studies with 1938 SLE patients and 3037 controls were included. Meta-analysis revealed that, compared with the control group, the OPN level was significantly higher in the SLE group (SMD = 0.965, 95% CI = 0.337-1.393, p = 0.001) and in the SLE group with renal disease (SMD = 2.219, 95% CI = 0.681-3.757, p = 0.005). Meta-analysis of correlation coefficients showed a trend of positive correlation between the circulating OPN level and SLEDAI (correlation coefficient = 0.590, 95% CI = -0.025 to 0.881, p = 0.059). While no association was found between SLE and the OPN 707 T/C and 1083 G/A polymorphisms, a significant association was identified between the OPN 1239 C allele and SLE (OR = 1.192, 95% CI = 1.008-1.410, p = 0.040), and between the OPN 9250 C allele and SLE in Asians (OR = 2.070, 95% CI = 1.570-2.730, p = 2.5 × 10-7). Conclusions Our meta-analysis revealed a significantly higher circulating OPN level in SLE patients, a trend of positive correlation between OPN levels and SLE activity, and a significant association between OPN 1239 C/A and 9250 C/T polymorphisms, and SLE development.
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