Yu David, Ekwall-Larson Anna, Özenci Volkan
Division of Clinical Microbiology, Department of Laboratory Medicine, Karolinska Institutet, SE-141 86 Stockholm, Hälsovägen, Stockholm, Sweden.
Functional Area of Perioperative Medicine and Intensive Care, Karolinska University Hospital, Stockholm, Sweden.
Eur J Clin Microbiol Infect Dis. 2024 Oct;43(10):1977-1987. doi: 10.1007/s10096-024-04916-6. Epub 2024 Aug 3.
Blood culture (BC) is the gold standard for diagnosing blood stream infections (BSI) but is limited by long turnaround times (TAT) and low detection rate. The T2 Magnetic Resonance method (T2MR) offers a rapid, culture-independent alternative. The objective of this study was to compare the performance of the T2Bacteria assay to BCs in a real-world setting.
Retrospective comparative study consisting of T2Bacteria samples and BCs sampled within 72 h from the T2Bacteria sample. The primary outcome was detections by BC and T2Bacteria, respectively. The secondary outcome was difference in TAT.
In total, 640 episodes were included, consisting of 640 T2Bacteria samples and 2,117 BCs. A median of three BCs was collected for each T2Bacteria sample. Overall positivity was 101 (15.8%) by either method. In 29 (28.7%) episodes, both T2Bacteria and BC were concordantly positive. In discordant episodes, 46/101 (45.5%) episodes were T2Bacteria positive/BC negative and 26/101 (25.7%) were T2Bacteria negative/BC positive (McNemar χ, p < 0,05). In T2Bacteria positive/BC negative episodes, eight had growth of the same microorganism in a non-BC culture. Median (IQR) TAT for BC was 35 h and 30 min (25 h 50 min - 45 h 24 min), compared to 21 h and 3 min (17 h 6 min - 27 h 30 m) for T2Bacteria (p < 0.001), with longer delays for samplings occurring outside work hours.
The study highlights a high discordance between T2Bacteria and BC and suggests complementary roles of the methods in BSI diagnostics. Furthermore, it is crucial to improve TAT by reducing preanalytical delays.
血培养（BC）是诊断血流感染（BSI）的金标准，但受周转时间（TAT）长和检测率低的限制。T2磁共振方法（T2MR）提供了一种快速、无需培养的替代方法。本研究的目的是在实际环境中比较T2细菌检测法与血培养的性能。
回顾性比较研究，包括T2细菌样本和在T2细菌样本采集后72小时内采集的血培养样本。主要结果分别是血培养和T2细菌检测法的检测结果。次要结果是周转时间的差异。
总共纳入640例，包括640个T2细菌样本和2117份血培养样本。每个T2细菌样本平均采集3份血培养样本。两种方法的总体阳性率为101例（15.8%）。在29例（28.7%）中，T2细菌检测法和血培养均为阳性。在不一致的病例中，46/101例（45.5%）为T2细菌检测法阳性/血培养阴性，26/101例（25.7%）为T2细菌检测法阴性/血培养阳性（McNemar检验χ，p＜0.05）。在T2细菌检测法阳性/血培养阴性的病例中，8例在非血培养中培养出相同微生物。血培养的中位（IQR）周转时间为35小时30分钟（25小时50分钟 - 45小时24分钟），而T2细菌检测法为21小时3分钟（17小时6分钟 - 27小时30分钟）（p＜0.001），工作时间外采样的延迟更长。
该研究突出了T2细菌检测法与血培养之间的高度不一致性，并表明这两种方法在血流感染诊断中具有互补作用。此外，通过减少分析前延迟来改善周转时间至关重要。
