Shaojie Li,1,* Hongjian Li,2,* Weizhi Qiu,1,* Baofang Wu,1 Jiayin Wang,1 Yasong Li,1 Hongzhi Gao1 

1Department of Neurosurgery, The Second Affiliated Hospital of Fujian Medical University, Quanzhou, Fujian, 362000, People’s Republic of China; 2School of Medical Imaging, North Sichuan Medical College, Nanchong, 634700, People’s Republic of China

*These authors contributed equally to this work

Correspondence: Yasong Li; Hongzhi Gao, Email 503553815@qq.com; gaohongzhi@fjmu.edu.cn

Background: Accurate identification of the risk of postoperative pneumonia (POP) in aneurysmal subarachnoid hemorrhage (aSAH) is essential for the implementation of stratified treatment. This study evaluated the relevance and utility of the Systemic Immuno-inflammatory Index (SII) and the Systemic Inflammatory Response Index (SIRI) in predicting pneumonia after aSAH.
Methods: Two hundred and forty patients undergoing aSAH intervention were included. Differences in SII and SIRI between patient groups were analyzed by propensity score matching (PSM). Receiver Operating Characteristic curves (ROC) were used to evaluate the predictive validity of SII and SIRI and to determine their predictive thresholds. The association of these indices with POP risk was assessed by multivariate logistic regression and restricted cubic spline (RCS), and subgroup analyses were performed.
Results: The overall POP prevalence was 60%, with 37.5% males and 62.5% females. PSM analyses showed statistically significant differences between the two groups for SII (P=0.032) and SIRI (P=0.02). They had a high predictive accuracy for predicting POP, with AUC values of 0.643 and 0.644, respectively. SII and SIRI were positively associated with the POP risk, independent of other confounders. Moreover, further sensitivity analysis and RCS supported the stability of this finding. Subgroup analyses showed that the relationship was stable across subgroups.
Conclusion: This study reveals the potential role of SII and SIRI in predicting the risk of postoperative pneumonia in patients with aSAH, and provides a strong basis for early identification and stratification of patients who are at high risk of postoperative pneumonia in aSAH.

Keywords: aneurysmal subarachnoid hemorrhage, interventional embolization, postoperative pneumonia, novel inflammatory index, correlation analysis