What is the link between the pro-inflammatory cytokine interleukin-6 (IL-6) and systemic lupus erythematosus (SLE)? Patients with SLE often have elevated levels of serum IL-6, but is there a direct correlation between this and the disease activity of SLE?
In a study published in Clinics, a team of researchers reviewed 24 studies published between 1996 and 2019 featuring 1817 patients with SLE and 874 healthy controls to determine if a relationship existed between the disease activity of SLE and higher levels of serum IL-6. For most of these studies, serum IL-6 levels were measured via enzyme-linked immunosorbent assay. Thirteen studies compared serum IL-6 levels of patients with SLE and healthy controls, and 9 studies compared serum IL-6 levels among patients with active and inactive SLE. Adult patients with SLE were included in 21 studies, and the remaining 3 focused on pediatric patients with SLE.
As the 13 studies comparing serum IL-6 between patients with SLE and healthy controls had such high heterogeneity, the researchers used a random-effects model for pooled analysis. They found that serum IL-6 levels in patients with SLE were much higher than those in healthy controls. This held true when the researchers performed subgroup analyses based on age, region (Asia or non-Asia), and measuring methods; subgroup analysis based on the definition of disease activity provided results that were deemed insignificant.
Random-effects models for pooled analysis were also used for the 9 studies comparing serum IL-6 levels in patients with active and inactive SLE; patients with active SLE had significantly higher levels of serum IL-6 than patients with inactive SLE.
In addition, 13 of the included studies used correlation coefficients to assess for a correlation between serum IL-6 levels and SLE disease activity. The researchers found a positive correlation between the two in these studies after using a random-effects model to pool analysis.
While the limitations of this study are acknowledged, the researchers believe they have quantitatively found a correlation between elevated serum IL-6 levels and SLE disease activity. They believe that this could have significance in terms of SLE treatment, providing not only a way to monitor disease activity but potentially making IL-6-targeted therapy useful in managing SLE.
Ding J, Su S, You T, et al. Serum interleukin-6 level is correlated with the disease activity of systemic lupus erythematosus: a meta-analysis. Clinics. 2020;75. doi:10.6061/clinics/2020/e1801