Nonlinear association between systemic immune-inflammation index and in-hospital mortality in critically ill patients with chronic obstructive pulmonary disease and atrial fibrillation: a cross-sectional study

Our findings position SII as a potentially valuable biomarker for risk stratification in patients with COPD and AF, with the identified threshold potentially serving as a clinical decision point for intensifying monitoring or considering immunomodulatory therapies. Future prospective studies should validate these findings and explore whether SII guided management improves outcomes in this high-risk population.