Abstract: Background　Lung infections mostly occur in the elderly， often in the form of comorbidities. Studies have shown that kidney function may affect the prognosis of patients with lung infections， but the mechanism of microbial changes in these patients still remains unclear，and there are few relevant reports in China. Objective　To investigate the relationship of specific etiological susceptibility and altered immune function with poor prognosis in elderly pulmonary infection patients with different estimated glomerular filtration rate. Methods　This retrospective，controlled and observational study was conducted with a cohort of elderly patients（over 65 years old）who were hospitalized due to pulmonary infection in the Second Medical Center，PLA General Hospital from January 2017 to December 2019. General conditions（gender and age），past medical history（chronic kidney disease，diabetes，dyslipidemia，chronic heart failure），and biochemical parameters detected after admission，including blood urea nitrogen（BUN），serum creatinine（Scr），aspartate aminotransferase（AST），alanine aminotransferase（ALT），serum albumin，estimated glomerular filtration rate（eGFR），routine blood parameters〔hemoglobin，white blood cell count，percentage of neutrophils，percentage of lymphocytes，total platelet count，neutrophil to lymphocyte ratio（NLR）〕and pathogenic microbes detected by sputum culture，as well as outcome（survival or death）acquired by a 90-day follow-up were collected. Multivariate Logistic regression analysis was used to explore the associated factors of death. ROC analysis of eGFR in predicting death was performed，and its optimal cut-off value was used to divide the cases into two groups〔eGFR≥47 ml•min-1•（1.73 m2）-1 and eGFR < 47 ml•min-1•（1.73 m2）-1〕 to compare intergroup differences in the distribution of pathogenic microbes and inflammatory indicators. Results　The prevalence of in-hospital death was 13.2%（68/514）. The deceased had younger mean age，lower prevalence of chronic kidney disease，higher mean levels of BUN，Scr，AST，ALT，white blood cell count and NLR，and lower mean levels of albumin，eGFR，hemoglobin and percentage of lymphocytes than survivors（P<0.05）. Multivariate Logistic regression analysis showed that age 〔OR=1.092，95%CI（1.027，1.162）〕，ALT 〔OR=1.013，95%CI（1.001，1.026）〕，albumin level〔OR=0.814，95%CI（0.759，0.873）〕，eGFR 〔OR=0.974，95%CI（0.961，0.988）〕，WBC count 〔OR=1.116，95%CI（1.030，1.210）〕and lymphocyte percentage 〔OR=0.011，95%CI（0，0.521）〕were associated with all-cause death（P<0.05）. The AUC of eGFR in predicting death was 0.614，with 47 ml•min-1•（1.73 m2）-1 was determined as the optimal cutoff value with 36.8% sensitivity，and 84.3% specificity. Compared to patients with eGFR≥47 ml•min-1•（1.73 m2）-1，those with eGFR<47 ml•min-1•（1.73 m2）-1 had higher prevalence of infection with Klebsiella pneumoniae，Escherichia coli，Staphylococcus aureus，and fungi and lower prevalence of infection with Pseudomonas aeruginosa（P<0.05）. Moreover，they also had higher mean percentage of neutrophils and NLR，as well as lower mean percentage of lymphocytes and platelet count（P<0.05）. Conclusion　Changes in immune function and susceptibility to Staphylococcus aureus infections in patients with low eGFR may be underlying causes of worsening prognosis in elderly people with pulmonary infection and reduced renal function.

Key words: Renal insufficiency, Pneumonia, Lung diseases, Aged, Prognosis

摘要： 背景　肺部感染多发于老年人，常以共病的形式存在，有研究显示肾功能可能会影响肺部感染患者的预后，但具体的微生物学改变机制仍不清楚，且目前国内关于该项研究的报道较少。目的　探讨不同估算肾小球滤过率（eGFR）的老年肺部感染患者特定病原学易感性及免疫系统功能改变与肺部感染不良预后的关系。方法　选择2017年1月至2019年12月，解放军总医院第二医学中心以肺部感染收住院的老年患者（年龄>65岁）514例为研究对象。收集患者一般情况（性别、年龄），既往病史（慢性肾脏病、糖尿病、血脂异常、慢性心力衰竭），入院后首次生化学检查〔血尿素氮（BUN）、血清肌酐（Scr）、天冬氨酸氨基转移酶（AST）、丙氨酸氨基转移酶（ALT）、血白蛋白、eGFR〕、血常规〔血红蛋白、白细胞计数、中性粒细胞百分比、淋巴细胞百分比、血小板计数、中性粒细胞与淋巴细胞比值（NLR）〕、病原微生物学（痰培养结果）指标。对所有研究对象进行为期90 d的电话随访，根据患者随访期间转归情况，分为生存组及死亡组，采用多因素Logistic回归分析探讨肺部感染患者全因死亡的影响因素；绘制eGFR预测老年肺部感染患者发生死亡事件的受试者工作特征曲线（ROC），并根据其最佳截断值将患者分为两组，分析两组患者病原微生物及炎性指标的分布情况。结果　514例患者中68例患者（13.2%）在住院期间死亡。死亡组患者年龄、合并慢性肾脏病比例、BUN、Scr、AST、ALT、白细胞计数、NLR高于生存组，白蛋白水平、eGFR、血红蛋白、淋巴细胞百分比低于生存组（P<0.05）。多因素Logistic回归分析结果显示，年龄〔OR=1.092，95%CI（1.027，1.162）〕、ALT〔OR=1.013，95%CI（1.001，1.026）〕、白蛋白水平〔OR=0.814，95%CI（0.759，0.873）〕、eGFR〔OR=0.974，95%CI（0.961，0.988）〕、白细胞计数〔OR=1.116，95%CI（1.030，1.210）〕、淋巴细胞百分比〔OR=0.011，95%CI（0，0.521）〕是老年肺部感染患者全因死亡的影响因素（P<0.05）。eGFR预测老年肺部感染患者发生死亡事件的ROC曲线下面积为0.614，最佳截断值为47 ml•min-1•（1.73 m2）-1，灵敏度为36.8%，特异度为84.3%。eGFR<47 ml•min-1•（1.73 m2）-1组患者肺炎克雷伯菌、大肠埃希菌、金黄色葡萄球菌、真菌感染比例高于eGFR≥47 ml•min-1•（1.73 m2）-1组，铜绿假单胞菌感染比例低于eGFR≥47 ml•min-1•（1.73 m2）-1组（P<0.05）。eGFR<47 ml•min-1•（1.73 m2）-1患者中性粒细胞百分比、NLR高于eGFR≥47 ml•min-1•（1.73 m2）-1组，淋巴细胞百分比、血小板计数低于eGFR≥47 ml•min-1•（1.73 m2）-1组（P<0.05）。结论　eGFR低的患者免疫功能的改变和对金黄色葡萄球菌感染的易感性，可能是老年肺部感染预后恶化的潜在原因。

关键词: 肾功能不全, 肺部感染, 肺疾病, 老年人, 预后