Clinical Evaluation of Digital PCR for Rapid Pathogen Detection in Suspected Bloodstream Infections

<b>Aims/Background</b> Bloodstream infection (BSI) is a life-threatening condition, and early, accurate pathogen identification is essential for improving patient outcomes. Conventional blood culture (BC) methods have notable limitations, including low sensitivity, prolonged turnaround time, and susceptibility to prior antibiotic exposure. This study aimed to evaluate the diagnostic performance and clinical value of digital polymerase chain reaction (dPCR) in patients with suspected BSI. <b>Methods</b> This retrospective study included 294 patients with suspected BSI admitted to the Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, between January 2021 and April 2022. All patients underwent BC and dPCR testing. dPCR was performed using a multiplex bacterial nucleic acid detection kit targeting <i>Escherichia coli</i>, <i>Klebsiella pneumoniae</i>, <i>Acinetobacter baumannii</i>, and <i>Pseudomonas aeruginosa</i>. BC results served as the reference standard, and discordant findings were resolved using Sanger sequencing. Sensitivity, specificity, overall agreement, and Kappa coefficients were analysed. The diagnostic efficacy of dPCR for localised infections was assessed, and univariate and multivariate logistic regression analyses were conducted to evaluate clinical predictors of dPCR positivity. <b>Results</b> Compared with BC, dPCR demonstrated a significantly higher positivity rate (41.5% vs. 12.2%). Validated against BC plus Sanger sequencing, dPCR achieved near-perfect sensitivity (99.18%) and specificity (99.42%), with an overall agreement of 99.32% (Kappa = 0.99). dPCR identified substantially more true-positive cases missed by BC (86 additional true positives and only one false positive). These patients had pathogens identified in other tissue samples, supporting the value of dPCR in early detection of occult infections. Multivariate analysis revealed elevated procalcitonin (PCT) as an independent predictor of dPCR positivity. The receiver operating characteristic (ROC) curve for PCT predicting dPCR positivity yielded an area under the curve (AUC) of 0.656 (95% confidence interval [CI]: 0.592-0.720, <i>p</i> < 0.001), with an optimal cut-off of 6.11 ng/mL. <b>Conclusion</b> dPCR demonstrates high sensitivity and accuracy for BSI diagnosis, allowing earlier detection of occult infections missed by conventional methods. Guided by clinical risk factors such as PCT, dPCR may refine diagnostic and treatment pathways for BSI.