New Inflammatory Marker Associated with Disease Activity in Rheumatoid Arthritis: The Systemic Immune-Inflammation Index.

Objective: This study aimed to discover a new index for disease activity by reviewing the relationship between the Systemic Immune-Inflammation Index and Systemic Inflammation Response Index in rheumatoid arthritis.

Method: A total of 109 patients with rheumatoid arthritis and 31 healthy controls were involved in the study. Based on disease activity score (DAS-28) calculated by the erythrocyte sedimentation rate, rheumatoid arthritis patients were divided into two groups: Group 1 comprised patients in remission (DAS-28<2.6); Group 2 was the active patient group (DAS-28>2.6). The Systemic Immune Inflammation Index and the Systemic Inflammation Response Index compared between the groups.

Results: The Systemic Immune-Inflammation Index is 666.415±33.00 in the patient group and 596.71±57.64 in the control group, and the difference between the groups is statistically significant (p=0.002). The Systemic Immune-Inflammation Index was 574.69±34.72 in group 1 and 702.25±39.56 in group 2. There was a significant statistical difference between the active and remission patients (p=0.030). The Systemic Inflammation Response Index was not statistically significant between the groups. Different cut-off points were compared to detect the optimal cut-off value for SII. Based on the ROC curve analysis, SII cut-off point of 574.20 showed 56.3% sensitivity and 45.5% specificity and with the Area Under Curve (AUC) 95% was the optimal cut-off point for active RA.

Conclusion: This is the first study to review the Systemic Immune-Inflammation Index in rheumatoid arthritis. The obtained conclusion verified that the Systemic Immune-Inflammation Index could be used as a new tool, showing disease activity.