高龄患者血培养实验室污染菌群分布与降钙素原鉴别血流感染和污染的价值

The Laboratory Contamination Bacterial Distribution of Blood Culture and Significance of PCT in the Differentiation of Blood Stream Infection and Contamination in Elderly Patients

目的分析高龄患者血培养标本中污染菌的菌种与分布,并对降钙素原(PCT)鉴别患者血流感染和血培养污染的诊断价值进行评价。方法前瞻性分析2016年9月至2017年12月入住北京市第二医院的高龄患者630例。所有患者抽取血培养,同时检测静脉血中PCT水平。依据实验室对血培养的判定原则并结合临床表现进行综合分析,判断血培养污染并分析其分布。以受试者工作特征曲线(ROC曲线)评价降钙素原鉴别高龄患者血流感染和血培养污染的诊断价值。结果血培养总计1322瓶,全部成套送检,成套率100%。血培养阳性率为13.9%,污染率为9.8%。污染菌以凝固酶阴性葡萄球菌和棒状杆菌较为多见。PCT鉴别高龄患者血流感染及污染的灵敏度为60.9%、特异性为83.1%、最佳阈值为0.659 ng/mL ,ROC曲线下面积(AUC)为0.740,准确性为中等。结论本院高龄患者血培养污染率高于国内相关文献报道,凝固酶阴性葡萄球菌是最常见的污染菌;PCT检测能够为临床鉴别高龄患者血流感染和血培养污染提供一定诊断价值。

Objective To investigate the bacterial contamination situation of blood culture,and to evaluate the value of procalcitonin(PCT)in differentiating bloodstream infection from contamination in elderly patients. Methods A perspective study with 630 elderly patients in the Second Hospital of Beijing from September,2016 to December,2017 was conducted.All patients were detected by blood culture and PCT.The comprehensive analysis was performed according to the laboratory assessment scheme on blood culture contamination and combining with the clinical data for judging the blood culture contamination and analyzing the bacterial species and their composition.Receiver operating characteristic(ROC)curve was used to analyze the diagnosis significance of blood stream infection and blood culture contamination in elderly patients. Results 1,322 bottles of blood culture were obtained and the complete set rate was 100%.The positive rate of blood culture was 13.9%,of which the contamination rate was 9.8%.The main contaminated bacteria were coagulase negative staphylococcus and Corynebacterium.The diagnostic sensitivity,specificity of PCT in differentiating bloodstream infection from contamination were 60.9%and 83.1%,respectively,with the best cutoff of 0.659 ng/mL.The area under ROC curve for PCT was 0.740.The accuracy of PCT for differentiating contamination from bloodstream infection was moderate. Conclusion The studied hospital has a higher blood culture contamination in elderly patients than previous reported results.The main contaminated bacteria are coagulase negative staphylococcus.PCT can be a valuable indicator for differentiating contamination from bloodstream infection in the case of elderly patients.