Systemic Immune-Inflammation Index in Assessing Disease Activity and Extraglandular Involvements in Primary Sjogrens Syndrome

To evaluate if the systemic immune inflammation index (SII) predicts extraglandular involvement and disease activity in primary Sjogren's Syndrome (pSS). Cross-sectional, observational study. Place and Duration of the Study: Department of Rheumatology, University of Health Sciences, Gulhane Training and Research Hospital, Ankara, Turkiye, from July 2022 to January 2023. This study included 102 healthy controls (HCs) and 128 pSS patients, matched for gender and age. SII, monocyte/ lymphocyte ratio (MLR), plateletcrit (PCT), neutrophil/lymphocyte ratio (NLR), and platelet/lymphocyte ratio (PLR) were calculated. The EULAR Sjogren's syndrome patient-reported index (ESSPRI) and the EULAR Sjogren's Syndrome disease activity index (ESSDAI) were used to measure disease activity. Logistic regression identified predictors of disease activity and extraglandular involvement. SII's diagnostic performance was evaluated via receiver operating characteristic curve analysis. Primary Sjogren's syndrome had higher NLR, MLR, SII, PLR, and PCT than HCs (all p <0.001). According to the ESSDAI, the SII was higher in moderate-to-severe disease activity (p <0.001). SII, with a moderate positive correlation between ESSDAI and ESSPRI, showed diagnostic performance when disease activity was assessed by both ESSDAI and ESSPRI (area under the curve: 0.930, 0.983, respectively, p <0.001). SII was associated with moderate-to-severe disease activity as well as pulmonary and neurological involvement. PLR was associated with skin involvement. The cut-off value of SII for predicting moderate-to-severe disease activity was 660.2 x 103 cells/µL. Haematological indices such as MLR, NLR, PLR, and PCT, especially SII, which are economical and practical, can be effective clinical assessment tools to monitor extraglandular involvement and disease activity. Systemic immune-inflammation index, Primary Sjogren's syndrome, Blood cell count, Pulmonary, Neurological involvement.