Correlation of serum adenosine deaminase activity with disease activity in patients with primary Sjögren's syndrome

Primary Sjögren's syndrome (pSS) is a chronic inflammatory autoimmune disease primarily affecting the exocrine glands, which has a variety of clinical manifestations and unclear pathogenic mechanisms. Adenosine deaminase (ADA) is an enzyme involved in the breakdown of purines, and changes in its activity have been associated with a number of autoimmune diseases. This study aims to investigate the relationship between serum ADA activity and disease activity in patients with pSS. In this study, 196 patients with pSS and 196 healthy controls were enrolled. Serum ADA activity and clinical laboratory parameters were collected and analyzed in both groups. Pearson correlation analysis was used to examine the correlation between ADA activity and clinical laboratory parameters, as well as the correlation between ADA activity and the disease activity score. Compared with healthy controls, the activity of ADA in the serum of pSS patients was significantly increased (P < 0.0001), and the ADA activity was significantly decreased after immunosuppressive treatment (P < 0.0001). Correlation analysis revealed that the activity of ADA was significantly positively correlated with erythrocyte sedimentation rate (ESR) (r = 0.3, P < 0.0001) and serum immunoglobulin G (IgG) levels (r = 0.5, P < 0.0001), and significantly negatively correlated with high-density lipoprotein (HDL) (r = −0.4, P < 0.0001). Furthermore, there was a significant positive correlation between ADA activity and the disease activity score as measured by the Sjögren's Syndrome Disease Activity Index (SSDAI) (r = 0.4, P < 0.0001). This study found that patients with pSS have higher activity of ADA in serum, which is associated with disease activity as measured by SSDAI. These results suggest that ADA activity may be a potential biomarker for evaluating disease activity and treatment efficacy in pSS patients. Additionally, ADA may be a potential target for the treatment of pSS patients.