Reliability of Droplet Digital PCR Alone and in Combination with Interleukin-6 and Procalcitonin for Prognosis of Bloodstream Infection

Abstract

Purpose

Bloodstream infection(BSI) is linked with high mortality, underscoring the significance of prompt etiological diagnosis for timely and precise treatment. This study aims to investigate the diagnostic value of droplet digital polymerase chain reaction(ddPCR) in combination with conventional inflammatory markers [interleukin-6(IL-6) and procalcitonin(PCT)] concerning disease progression and treatment prognosis in BSI patients. Furthermore, the study aims to explore a more efficient clinical application strategy.

Patients and Methods

This prospective case seried study centers on 176 patients suspected of or confirmed with BSI. Blood samples were collected to extract nucleic acids for identifying pathogens (bacteria, fungi, and viruses) and determining copy loads via ddPCR.

Results

The sensitivity of ddPCR was markedly higher compared to the culture method (74.71% vs 31.03%). A positive correlation existed between bacterial load and levels of inflammatory markers [IL-6 (P=0.0182), PCT (P=0.0029), and CRP (P=0.0005)]. In suspected BSI cases, the combination of ddPCR and inflammatory markers could predict sepsis risk [ROC: Area under the curve(AUC)=0.6071, P=0.0383]. Within confirmed BSI patients, the ddPCR bacterial load of those with SOFA<7 was lower than that of the SOFA≥7 (P=0.0334). ddPCR (OR: 1.789, P=0.035) monitoring combined with PCT (OR: 1.787, P=0.035) holded predictive value for SOFA progression (AUC=0.7913, P=0.0003). Similarly, BSI survivors displayed a lower burden than non-survivors (P=0.0170). Additionally, ddPCR combinated with IL-6 provided a more accurate and expedited insight into clinical outcomes prediction for BSI confirmed patients (AUC=0.7352, P=0.0030). Serial monitoring of bacterial load by ddPCR effectively mirrored the clinical course of BSI in patients. Notably, patients with positive ddPCR virus infection exhibited significantly reduced lymphocyte counts (P=0.0003).

Conclusion

In a clinical context, qualitative ddPCR results and quantitative continuous monitoring can more precisely assess sepsis progression and treatment prognosis in BSI patients. Furthermore, ddPCR results offer quicker and more accurate reference points for clinical antibacterial and antiviral interventions.

Keywords:

• bloodstream infection
• droplet digital polymerase chain reaction
• interleukin-6
• procalcitonin
• prognosis

Abbreviations

BSI, Bloodstream infection; ddPCR, Droplet digital polymerase chain reaction; IL-6, Interleukin-6; PCT, Procalcitonin; AUC, Area under the curve; SOFA, Sequential Organ Failure Assessment; TAT, Turnaround time; CRP, C-reactive protein; AMR, Antimicrobial resistance; ICU, Intensive care unit; PCR, Polymerase chain reaction; ROC, Receiver operating characteristic; EBV, Epstein-Barr virus; CMV, Cytomegalovirus; HSV, Herpes simplex virus; VZV, Varicella-zoster virus.

Data Sharing Statement

The data that support the findings of this study are available from the corresponding author upon reasonable request.

Ethics approval and informed consent

This was a single-center prospective cohort study conducted at a teaching hospital in Changsha, China. The study protocol was reviewed and approved by the Hospital Ethics Committee (Ethical Review Committee of the Second Xiangya Hospital of Central South University, Changsha, China, No. 2022xyeyy051). The study enrolled hospitalized patients over 18 years old with suspected BSI from November 2022 to February 2023.

Consent for Publication

All participants consented to the publication of the raw data from the assay. This study has protected patient personal information. The patient number and other information involved are replaced by the sample number.

Acknowledgments

We would like to express our gratitude to Pilot Gene Technology [Hangzhou] Co., Ltd., Hangzhou, China for providing us with technical support and guidance during the course of this study. We express our gratitude to the Molecular Biology Department, Microbiology Department, and Clinical Blood Department at the Second Xiangya Hospital of Central South University for providing their invaluable support to this study.

Author Contributions

All authors made a significant contribution to the work reported, whether that is in the conception, study design, execution, acquisition of data, analysis and interpretation, or in all these areas; took part in drafting, revising or critically reviewing the article; gave final approval of the version to be published; have agreed on the journal to which the article has been submitted; and agree to be accountable for all aspects of the work.

Disclosure

All the authors have no conflict of interest.

Additional information

Funding

This work was supported by grants from the Hunan Provincial Department of Finance Project (Grant No. 202065), the Natural Science Foundation of China (Grant No. 82270840), Changsha Natural Science Foundation (Grant NO. kq2202414), and the Fundamental Research Funds for the Central Universities of Central South University (Grant NO. 1053320212719).