Low NAPR as a Novel Indicator for Predicting Escherichia coli Bloodstream Infection and Improved Prognostic Outcomes in Elderly Hospitalized Inpatients: A 12-years Retrospective Cohort Study

Xinjie Han,1– 3,* Yang Yang,4,* Jianbo Zhong,2,5,* Zhenghao Yu,1,2 Pinzheng Zhang,5 Xinran Liu,2,5 Yongkai Ding,2,5 Qi Zhang,6 Pingjun Zhu,4 Guogang Xu,1 Yingzhen Du2,5,7 1Health Management Institute, The Second Medical Center and National Clinical Research Center for Geriatric Diseases, Chinese PLA General Hospital, Beijing, 100853, People’s Republic of China; 2Chinese PLA General Hospital, Medical School of Chinese PLA, Beijing, 100853, People’s Republic of China; 3Department of Respiratory and Critical Care Medicine, The Eighth Medical Center, Chinese PLA General Hospital, Beijing, 100853, People’s Republic of China; 4Department of Respiratory and Critical Care Medicine, The Second Medical Center and National Clinical Research Center for Geriatric Diseases, Chinese PLA General Hospital, Beijing, 100853, People’s Republic of China; 5Department of Disease Prevention and Control, The Second Medical Center and National Clinical Research Center for Geriatric Diseases, Chinese PLA General Hospital, Beijing, 100853, People’s Republic of China; 6The Second Medical Center and National Clinical Research Center for Geriatric Diseases, Chinese PLA General Hospital, Beijing, 100853, People’s Republic of China; 7Fever Clinic, The Second Medical Center and National Clinical Research Center for Geriatric Diseases, Chinese PLA General Hospital, Beijing, 100853, People’s Republic of China*These authors contributed equally to this workCorrespondence: Guogang Xu, Email [email protected] Yingzhen Du, Email [email protected]: Bloodstream infections (BSIs) are associated with significant mortality, particularly in elderly patients. Escherichia coli (E.coli) is the most common causative organism in BSIs, but non-E.coli BSIs are associated with increased morbidity and mortality. Predictive biomarkers including the neutrophil-to-platelet ratio (NPAR) have not been well studied in elderly hospitalized patients. Our study aimed to compare the mortality in patients with E.coli and non-E.coli BSIs and, evaluate NPAR as a potential predictive biomarker for E.coli infection in extremely elderly inpatients.Methods: A single-center, retrospective cohort study was conducted, involving 510 elderly patients diagnosed with bloodstream infections. Patients were divided into two groups based on the pathogen responsible for the infection: E.coli (n=92) and non-E.coli (n=418). Clinical data, comorbidities, and laboratory parameters were systematically collected. Kaplan-Meier survival analysis and Cox proportional hazards models were used to assess mortality risk, adjusting for relevant confounding variables. The predictive value of NPAR for E.coli bloodstream infection was analyzed via odds ratios (OR) and trend tests. Microbiological analysis of blood samples was performed according to the Clinical and Laboratory Standards Institute protocols.Results: Non-E.coli BSIs was associated with greater mortality compared to E.coli BSI; hazard ratio (HR)=0.43 (95% CI=0.21, 0.88; P=0.021). NPAR was a significant predictor of E.coli BSI; for continuous NPAR, the odds of E.coli BSI decreased by 12% per unit increase in NPAR (OR=0.88; 95% CI=0.84, 0.93; P< 0.001). The odds ratio of the lowest tertile of NPAR versus rest was 0.21 (95% CI=0.11, 0.40, P< 0.001).Conclusion: Non-E.coli BSIs are associated with greater mortality in elderly patients, while low NPAR is strongly associated with E.coli BSI. These findings suggest that NPAR may be useful for early risk stratification and clinical management of elderly patients with BSIs.Keywords: bloodstream infection (BSI), Escherichia coli, neutrophil-to-platelet ratio (NPAR), elderly, retrospective cohort study