Abstract: Objective To evaluate the predictive value of the systemic immune-inflammatory index (SII) and prognostic nutritional index (PNI) in identifying hospital-acquired pneumonia (HAP) in elderly patients with acute heart failure (AHF). Methods A total of 122 elderly AHF patients admitted to Nanjing’s Hospital of Nanjing Medical University from March 2020 to March 2023 were enrolled as the training set and were divided into an infected group (n=54) and an uninfected group (n=68) based on whether they had HAP. Logistic regression was used to identify risk factors for HAP and a prediction model was developed. The model was validated in an independent cohort of 80 patients admitted from April 2023 to March 2024. The performance of the model was assessed by the area under the receiver operating characteristic curve (AUC). Calibration and consistency between the training and validation sets were evaluated by Hosmer-Lemeshow and DeLong tests, respectively. Results The infected group and the uninfected group showed significant differences in age, smoking history, comorbidities, cardiac function, and inflammatory/nutritional parameters (all P<0.05). Multivariate logistic regression analysis identified age ≥66 years old, diabetes, invasive procedures, SII≥346, and PNI <43 as independent risk factors for HAP. The model demonstrated strong discrimination power, with an AUC of 0.829 in the training set and 0.830 in the validation set. Delong test revealed no significant difference in AUC between the two sets (P=0.990). Good calibration was confirmed by Hosmer-Lemeshow test (P=0.056, 0.159). Conclusions The prediction model based on SII and PNI effectively stratifies HAP risk in elderly AHF patients, showing good clinical applicability for early identification of high-risk individuals and optimized management.

Key words: aged, heart failure, hospital-acquired pneumonia, systemic immune inflammatory index, prognostic nutritional index