Prognostic Value of SII, SIAI, and Hematological Markers in Septic and Rheumatoid Arthritis: A Comparative Sensitivity Analysis

Background: The study aimed to compare the prognostic significance of Systemic Immune Inflammation Index (SII), Systemic Inflammation Aggregate Index (SIAI) with hematological markers in patients with septic arthritis and rheumatoid arthritis, and the sensitivity of the indices in predicting disease outcomes. Methods: 92 patients with septic arthritis,110 patients with rheumatoid arthritis were included in the study. Demographic data, hematological parameters and inflammatory markers were evaluated. SII, SIAI were calculated. Results: The mean age in the study was 58.60 ± 17.54 years, most It was a woman. Septic arthritis was more common in older men and rheumatoid arthritis was more common in younger women. Showed markedly elevated WBC, neutrophil and monocyte levels in septic arthritis. Elevated WBC, neutrophil and monocyte levels were higher in septic arthritis patients. The mean lymphocyte count was high in patients with rheumatoid arthritis, lymphocyte decrease was common in patients with septic arthritis. Higher platelet count seen in septic arthritis. Mean MPV was lower in septic arthritis patients. RDW-CV and RDW-SD were significantly higher in rheumatoid arthritis patients. PCT, NLR, PLR, MLR, MPR, SII and SIAI values ​​were significantly higher in septic arthritis patients; this reflected greater immune activation in infection-induced inflammation. The proportion of patients with ESR and CRP was significantly higher in septic arthritis, revealing the intensity of the inflammatory response. Conclusions: The study highlights the understanding of different immune mechanisms in septic and rheumatoid arthritis, the diagnostic value of specific hematological markers, the impact of demographic factors on disease distribution.