Kitaura Tsuyoshi, Chikumi Hiroki, Fujiwara Hiromitsu, Okada Kensaku, Hayabuchi Tatsuya, Nakamoto Masaki, Takata Miyako, Yamasaki Akira, Igishi Tadashi, Burioka Naoto, Shimizu Eiji
Division of Medical Oncology and Molecular Respirology, Department of Multidisciplinary Internal Medicine, School of Medicine, Tottori University Faculty of Medicine, Yonago 683-8504, Japan.
Division of Medical Oncology and Molecular Respirology, Department of Multidisciplinary Internal Medicine, School of Medicine, Tottori University Faculty of Medicine, Yonago 683-8504, Japan ; †Center for Infectious diseases, Tottori University Hospital, Yonago 683-8504, Japan.
Yonago Acta Med. 2014 Dec;57(4):159-65. Epub 2014 Dec 26.
Performing multiple blood culture sets simultaneously is a standard blood culture methodology, although it is often difficult to distinguish true bacteremia from contamination when only one of several blood culture sets is positive. This study clarified the relationship between the number of positive blood culture sets and clinical significance in patients with positive blood culture.
Patients aged 18 years and over with at least 1 positive blood culture were enrolled. Positive blood culture episodes were categorized from clinical records as true bacteremia, contamination, or unknown clinical significance. The associations among episodes of true bacteremia, isolated bacteria, the number of positive blood culture sets from among the performed sets, and the clinical background of patients were analyzed.
Among a total of 407 episodes, 262, 67 and 78 were true bacteremia, contamination and unknown clinical significance, respectively. The positive predictive values (PPVs) of 1 out of 1, 1 out of 2 and 2 out of 2 positive sets in cases of Staphylococcus aureus, were 81.3%, 50% and 100% respectively; those in cases of coagulase-negative Staphylococci were 20.5%, 10.8% and 63.5%, respectively. Almost all cases of Escherichia coli, Pseudomonas aeruginosa, Klebsiella species and Candida species were true bacteremia. The probability of true bacteremia was strongly associated with recent surgery in multivariate analysis (P < 0.05).
The probability of true bacteremia based on the number of positive culture sets from among the performed sets varies by microorganism. Therefore, PPVs calculated using this method may help physicians distinguish true bacteremia from contamination.
同时进行多组血培养是标准的血培养方法，不过当多组血培养中只有一组呈阳性时，往往很难区分是真性菌血症还是污染。本研究阐明了血培养阳性患者中阳性血培养组数量与临床意义之间的关系。
纳入年龄在18岁及以上且至少有1次血培养阳性的患者。根据临床记录将血培养阳性发作分为真性菌血症、污染或临床意义不明。分析真性菌血症发作、分离出的细菌、所进行的血培养组中阳性血培养组的数量以及患者的临床背景之间的关联。
在总共407次发作中，分别有262次、67次和78次为真性菌血症、污染和临床意义不明。金黄色葡萄球菌病例中，1组阳性中的1次阳性、2组阳性中的1次阳性和2组阳性中的2次阳性的阳性预测值（PPV）分别为81.3%、50%和100%；凝固酶阴性葡萄球菌病例中的PPV分别为20.5%、10.8%和63.5%。几乎所有大肠杆菌、铜绿假单胞菌、克雷伯菌属和念珠菌属病例均为真性菌血症。在多因素分析中，真性菌血症的概率与近期手术密切相关（P < 0.05）。
根据所进行的血培养组中阳性培养组数量得出的真性菌血症概率因微生物而异。因此，使用此方法计算的PPV可能有助于医生区分真性菌血症和污染。
