Are there differences in the clinical and laboratory features of patients with seronegative primary Sjögren's syndrome?

Achoimre

Background/aim: The primary objective of this study was to demonstrate the commonalities and distinctions between patients with seronegative and seropositive primary Sjögren's syndrome (pSS).Materials and methods: Between January 2010 and June 2023, 399 pSS were retrospectively examined. Patients with negative anti-SSA/Ro, anti-SSB/La, ANA, and RF antibodies comprised the seronegative group, while patients with at least one antibody positivity classified the seropositive group.Results: The most common clinical features were arthralgia (81.2%), arthritis (11.5%), hematological (19.8%) and pulmonary (11.8%) involvement. In 41 patients (10.3%), no autoantibody positivity was detected. The number of patients with at least one extraarticular involvement was statistically more frequent in the seropositive group (p=0.011). Dry mouth was found to be more prevalent among seronegative patients (p=0.003). While hyperimmune gammaglobulinemia exhibited a higher prevalence within the seropositive group (p=0.004), the occurrence of reduced complement levels demonstrated similar rates in both groups. All deaths that occurred were observed exclusively within the seropositive group (17/358, 4.7%). No difference was observed between the two groups concerning mortality (p=0.237) and the malignancies (seropositive group:9/358, 2.5% vs seronegative group:3/41, 7.3%, p=0.115). There was a statistically significant association between low C4 levels (OR=2.99 [1.09-8.16], p=0.045 in Model 1, OR=3.10 [1.14-8.42], p=0.022 in Model 2), and extraarticular findings.Conclusion: In conclusion, while hematologic, renal, pulmonary, and neurological involvements are observed with similar frequency in both seronegative and seropositive pSS patients, the presence of any extra-articular manifestations was more common in seropositive patients. Additionally, there was a relationship between extra-articular involvement and low C4 levels.