Background/Purpose: The systemic immune-inflammation index (SII) has been linked to inflammatory and immune responses, with research indicating its impact on rheumatoid arthritis (RA). However, its prognostic significance in severe RA patients requiring intensive care unit (ICU) admission remains uncertain. This study aims to explore the correlation between SII and all-cause mortality in critically ill patients with RA.

Methods: This study identified patients with severe RA requiring ICU admission from the Medical Information Mart for Intensive Care (MIMIC-IV) database, and divided them into quartiles based on SII level. The outcomes included all-cause mortality at 28, 90, and 360 days post-admission. We utilized multivariate regression to explore the link between the SII and RA, enhanced by subgroup and interaction analyses to reveal patient-specific and combined effects of SII on RA outcomes. Additionally, the restricted cubic splines were used to explore whether there were linear or non-linear relationships between SII and mortality.

Results: A total of 400 patients (70.3% female) were enrolled. The multivariate logistic regression analysis showed that highest quartile, exhibited a significant increase in the risk of 360-day mortality across all models. Restricted cubic splines revealed the relationship between SII and RA was non- linear. Subgroup analysis revealed similar outcomes in diverse RA patient groups, especially among whites, those aged over 60, and hypertensive individuals. A significant multiplicative interaction was observed between SII and age (P < 0.001).

Conclusion: The study demonstrates that the SII serves as a valuable and accessible inflammatory biomarker for predicting all-cause mortality risk in critically ill patients with RA.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/association-between-the-systemic-immune-inflammatory-index-sll-and-all-cause-mortality-in-critically-ill-patients-with-rheumatoid-arthritis/