This retrospective cohort study investigated the relationship between systemic immune inflammation index (SII) and prolonged length of hospital stay in patients with acute exacerbation of chronic obstructive pulmonary disease (AECHOCP), with prolonged length of stay defined as more than 7 days.[2] Complete blood counts were obtained within 24 hours of patient admission to calculate SII, which was logarithmically transformed to In-SII.[2] The results showed that high In-SII values are an independent risk factor for prolonged hospital stay in patients with AECHOHP, and its predictive performance is better than that of the neutrophil-to-lymphocyte ratio (In-NLR) index.[2] Analysis using restricted cubic splines confirmed a linear relationship between In-SII and length of hospital stay.[2] Decision curve analysis demonstrated significant clinical benefit when the In-SII threshold ranged from 0.41 to 0.80.[2] The study concluded that AECHOCP patients with high SII levels have worse outcomes and require earlier implementation of more stringent intervention measures and close monitoring of disease progression.[2]