Background and Aims: Matrix metalloproteinase-9 (MMP-9) is closely related to the pathogenesis of
autoimmune diseases, especially Systemic Lupus Erythematosus (SLE). However, published works about the
circulating MMP-9 levels in SLE are contradictory. A meta-analysis was performed to estimate circulating MMP-
9 levels in SLE patients more accurately and explore its related influencing factors.
Methods: The related literatures were systematically searched in PubMed, Embase, and The Cochrane Library
database (up to 31 January 2018). Pooled Standardized Mean Difference (SMD) and 95% Confidence Interval
(CI) of circulating MMP-9 levels were calculated by Stata12.0 software according to fixed-effect or randomeffect
Results: A total of 638 articles were retrieved, and 12 studies including 730 SLE cases and 759 controls were
finally included in the meta-analysis. No significant differences in circulating MMP-9 levels were observed between
SLE patients and healthy controls (pooled SMD = -0.209, 95% CI = -0.812 to 0.394). However, subgroup
analyses indicated that age<30 years group had higher MMP-9 levels (SMD = 0.991, 95% CI: 0.504 to 1.478) and
sample size (n ≥ 60) group had lower MMP-9 levels when compared with controls (SMD = -0.755, 95% CI: -
1.347 to -0.163).
Conclusion: The meta-analysis of current evidence suggests that circulating MMP-9 levels do not differ between
SLE patients and healthy controls, however, the results may be affected by age and sample size. Further studies
are needed to clarify the relationship between SLE and circulating MMP-9 levels.