OR (95%CI) - odds ratio with corresponding 95% confidence interval. IL-6 - interleukin-6. ESR - erythrocyte sedimentation rate. RF - rheumatoid factor. CRP - C-reactive protein. C3 - complement component C3. C4 - complement component C4. ESSDAI - European League Against Rheumatism - EULAR Sjögren’s Syndrome Disease Activity Index. ESSPRI - EULAR Sjögren ́s Syndrome Patient Reported Index. P < 0.05 was considered statistically significant. This evidence concerns the gene C4A and Sjogren syndrome.