Among patients with systemic autoimmune rheumatic diseases (SARDs), treatment with tumor necrosis factor inhibitors (TNFis) increases serum uric acid (SUA) levels, according to study results published in Rheumatology International.

However, the results of the study did not indicate that increased SUA levels were caused by the measured proinflammatory cytokines or the oxidation to stress marker allantoin.

The study included patients (n=128) with active SARDs initiating TNFi treatment. After 3 months of treatment, the researchers measured SUA levels, C-reactive protein (CRP), creatinine, proinflammatory cytokine concentrations, including monocyte chemoattractant protein (MCP)-1, interferon (IFN)-α2, IFN-γ, interleukin (IL)-1β, IL-6, IL-8, IL-10, IL-12p70, IL-17a, IL-18, IL-23, IL-33, TNF-α, and allantoin levels at baseline. They then tested these levels for associations with demographic and disease-related data.

Among the 128 patients, 44 had rheumatoid arthritis, 45 had ankylosing spondylitis, 23 had psoriatic arthritis, and 16 were adults with juvenile idiopathic arthritis.

After 3 months of treatment, the researchers found that SUA levels significantly increased from 279.5 μmol/L to 299.0 μmol/L (P <.0001). They also found that levels of CRP (31.2 vs 2.3 mg/L; P <.0001), IL-6 (62.0 vs 13.3 pg/mL; P <.0001), IL-8 (82.9 vs 57.2 pg/mL; P =.0117), and MCP-1 (962.6 vs 878.7 pg/mL; P =.0016) significantly decreased after 3 months.

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In both the univariate and multivariate models, the results indicated that the most significant baseline predictor of ΔSUA was male sex. The researchers did not find that any measured laboratory-based parameters had statistically significant effects on the magnitude of ΔSUA.

“Further studies are needed to clarify the pathophysiology of lowering of SUA levels during a [systemic inflammatory response],” the researchers wrote.

Reference

Hasikova L, Pavlikova M, Hulejova H, et al. Serum uric acid increases in patients with systematic autoimmune rheumatic diseases after 3 months of treatment with TNF inhibitors [published online July 31, 2019]. Rheumatol Int. doi:10.1007/s00296-019-04394-6