Droplet digital PCR (ddPCR) has emerged as a promising tool of pathogen detection in bloodstream infections (BSIs) in critical care medicine. However, different ddPCR platforms have variable sensitivity and specificity for diverse microorganisms at various infection sites. There is still a lack of prospective clinical studies aimed at validating and interpreting the discrepant ddPCR results for diagnosing BSI in intensive care unit (ICU) practice. A prospective diagnostic study of multiplex ddPCR panels was conducted in a general ICU from May 21, 2021, to December 22, 2021. Paired blood cultures (BCs) and ddPCRs (2.5 h) were obtained synchronously to detect the 12 most common BSI pathogens and three antimicrobial resistance (AMR) genes. Firstly, ddPCR performance was compared to definite BSI. Secondly, clinical validation of ddPCR was compared to composite clinical diagnosis. Sensitivity, specificity, and positive and negative predictive values were calculated. Thirdly, the positive rate of AMR genes and related analysis was presented. A total of 438 episodes of suspected BSIs occurring in 150 critical patients were enrolled. BC and ddPCR were positive for targeted bacteria in 40 (9.1%) and 180 (41.1%) cases, respectively. There were 280 concordant and 158 discordant. In comparison with BCs, the sensitivity of ddPCR ranged from 58.8 to 86.7% with an aggregate of 72.5% in different species, with corresponding specificity ranging from 73.5 to 92.2% with an aggregate of 63.1%. Furthermore, the rate of ddPCR+/BC− results was 33.6% (147/438) with 87.1% (128 of 147) cases was associated with probable (n = 108) or possible (n = 20) BSIs. When clinically diagnosed BSI was used as true positive, the final sensitivity and specificity of ddPCR increased to 84.9% and 92.5%, respectively. In addition, 40 blaKPC, 3blaNDM, and 38 mecA genes were detected, among which 90.5% were definitely positive for blaKPC. Further, 65.8% specimens were predicted to be mecA-positive in Staphylococcus sp. according to all microbiological analysis. The multiplexed ddPCR is a flexible and universal platform, which can be used as an add-on complementary to conventional BC. When combined with clinical infection evidence, ddPCR shows potential advantages for rapidly diagnosing suspected BSIs and AMR genes in ICU practice.

中文翻译：

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用于诊断 ICU 实践中疑似血流感染的多重液滴数字 PCR 的临床验证：一种有前途的诊断工具

液滴数字 PCR (ddPCR) 已成为重症监护医学中血流感染 (BSI) 病原体检测的有前途的工具。然而，不同的 ddPCR 平台对不同感染部位的不同微生物具有不同的敏感性和特异性。仍然缺乏旨在验证和解释在重症监护病房 (ICU) 实践中诊断 BSI 的差异 ddPCR 结果的前瞻性临床研究。2021 年 5 月 21 日至 2021 年 12 月 22 日，在普通 ICU 进行了一项多重 ddPCR 面板的前瞻性诊断研究。同步获得配对血培养 (BCs) 和 ddPCRs (2.5 h)，以检测 12 种最常见的 BSI 病原体和三个抗菌素耐药性（AMR）基因。首先，将 ddPCR 性能与确定的 BSI 进行比较。第二，将ddPCR的临床验证与复合临床诊断进行比较。计算敏感性、特异性以及阳性和阴性预测值。三是AMR基因阳性率及相关分析。共招募了 150 名危重患者中发生的 438 次疑似 BSI 事件。BC 和 ddPCR 分别在 40 例 (9.1%) 和 180 例 (41.1%) 病例中对靶向细菌呈阳性。有 280 个一致和 158 个不一致。与BCs相比，ddPCR在不同物种中的敏感性为58.8%~86.7%，合计为72.5%，相应的特异性为73.5%~92.2%，合计为63.1%。此外，ddPCR+/BC- 结果率为 33.6% (147/438)，其中 87.1% (147 例中的 128 例) 与可能 (n = 108) 或可能 (n = 20) BSI 相关。当临床诊断的 BSI 被用作真阳性时，ddPCR 的最终敏感性和特异性分别增加到 84.9% 和 92.5%。此外，共检测到40个blaKPC、3blaNDM和38个mecA基因，其中90.5%为blaKPC肯定阳性。此外，预计 65.8% 的标本在葡萄球菌属中为 mecA 阳性。根据所有微生物分析。多路复用 ddPCR 是一个灵活且通用的平台，可用作对传统 BC 的补充。当与临床感染证据相结合时，ddPCR 显示出在 ICU 实践中快速诊断疑似 BSI 和 AMR 基因的潜在优势。共检测出38个mecA基因，其中90.5%为blaKPC阳性。此外，预计 65.8% 的标本在葡萄球菌属中为 mecA 阳性。根据所有微生物分析。多路复用 ddPCR 是一个灵活且通用的平台，可用作对传统 BC 的补充。当与临床感染证据相结合时，ddPCR 显示出在 ICU 实践中快速诊断疑似 BSI 和 AMR 基因的潜在优势。共检测出38个mecA基因，其中90.5%为blaKPC阳性。此外，预计 65.8% 的标本在葡萄球菌属中为 mecA 阳性。根据所有微生物分析。多路复用 ddPCR 是一个灵活且通用的平台，可用作对传统 BC 的补充。当与临床感染证据相结合时，ddPCR 显示出在 ICU 实践中快速诊断疑似 BSI 和 AMR 基因的潜在优势。