Objective To investigate the predictive value of systemic immune-inflammation index(SII)combined with albumin(ALB)in the severity of community-acquired pneumonia(CAP)in elderly patients.Methods A retrospective analysis was conducted on 184 elderly patients with CAP in the Respiratory and E-mergency Medicine departments of the hospital from January 2023 to May 2024.According to the 2016 Chi-nese Adult CAP Diagnosis and Treatment Guidelines,patients were divided into severe CAP group(n=76)and non-severe CAP group(n=108).Basic information of patients was collected,routine blood tests and blood biochemical parameters were collected within 24 hours after admission,and the differences in SII,SIRI,hyper-sensitive CRP,and ALB were compared between the two groups.The ROC curve was applied to calculate the area under the curve and analyze the value of SII,SIRI,hypersensitive CRP,and ALB in predicting severe CAP.Results In terms of inflammation indicators,SII,SIRI,hs-CRP,and neutrophil count in the severe CAP group were higher than those in the non-severe CAP group(P<0.05),while lymphocyte count was lower than that in the non-severe CAP group(P<0.05).In terms of blood biochemistry,serum creatinine and BUN in the severe CAP group were higher than those in the non-severe CAP group,while ALB was lower than that in the non-severe CAP group(P<0.05).Binary logistic regression analysis showed that SII and ALB were in-dependent influencing factors for the severity of CAP in elderly patients(P<0.05).The ROC curve showed that the AUC of SII and ALB for predicting severe CAP in the elderly was 0.863 and 0.906,respectively,and the combined AUC was 0.937(0.904,0.970),with a sensitivity of 0.842 and a specificity of 0.880.Conclusion SII combined with ALB can serve as a predictor for early disease severity in elderly patients with CAP.