Rapid detection and ruling out of neonatal sepsis by PCR coupled with Electrospray Ionization Mass Spectrometry (PCR/ESI-MS)

Molecular assays for the diagnosis of sepsis in neonates: a diagnostic test accuracy review

BACKGROUND

Microbial cultures for diagnosis of neonatal sepsis have low sensitivity and reporting delay. Advances in molecular microbiology have fostered new molecular assays that are rapid and may improve neonatal outcomes.

OBJECTIVES

To assess the diagnostic accuracy of various molecular methods for the diagnosis of culture-positive bacterial and fungal sepsis in neonates and to explore heterogeneity among studies by analyzing subgroups classified by gestational age and type of sepsis onset and compare molecular tests with one another.

SEARCH METHODS

We searched CENTRAL, MEDLINE, Embase and trial registries in August 2023. We checked reference lists of included studies and systematic reviews where subject matter related to the intervention or population examined in this review.

SELECTION CRITERIA

We included studies that were prospective or retrospective, cohort or cross-sectional design, which evaluated molecular assays (index test) in neonates with suspected sepsis in comparison with microbial cultures (reference standard).

DATA COLLECTION AND ANALYSIS

Two review authors independently screened studies, extracted data and assessed the methodological quality of the studies. We performed meta-analyses using the bivariate model and entered data into Review Manager.

MAIN RESULTS

Seventy-four studies were eligible for inclusion, of which 68 studies provided data for meta-analysis. The total number of participants was 14,309 (1328 infants who were culture-positive and 12,981 infants who were culture-negative) from 68 studies that were included in the meta-analysis. The summary estimate of sensitivity was 0.91 (95% confidence interval (CI) 0.85 to 0.95) and of specificity was 0.88 (95% CI 0.83 to 0.92) (low-certainty evidence). We explored heterogeneity by subgroup analyses of type of test, gestational age, type of sepsis onset and prevalence of sepsis. We found insufficient explanations for the heterogeneity (low- to very low-certainty evidence). Sensitivity analyses including studies that analyzed blood samples, using good methodology and those that did not use multiple samples from the same participant revealed similar results (low-certainty evidence).

AUTHORS' CONCLUSIONS

Molecular assays have the advantage of producing rapid results and have moderate diagnostic accuracy. Molecular assays may prevent overuse of antibiotics in neonates with suspected sepsis. The efficacy and cost-effectiveness of these molecular assays should be evaluated using randomized trials comparing molecular assays as an add-on test versus conventional methods without the add-on test in neonates with suspected sepsis.

Rapid molecular assays versus blood culture for bloodstream infections: a systematic review and meta-analysis

Background

Timely management of sepsis with early targeted antimicrobial therapy improves patient outcomes. Rapid molecular assays (RMAs) have emerged, enabling the detection of bloodstream infection (BSI) with a shorter turnaround time than blood cultures (BCs). The accuracy of several RMAs has not been comprehensively reviewed. We aimed to identify commercial RMAs reported in the literature and evaluate their diagnostic performance compared to BC.

Methods

A systematic review and meta-analysis was conducted, covering MEDLINE, Cochrane Library, Embase, and Web of Science from inception to September 23, 2024. Eligible studies included patients with suspected or documented BSI, tested with both an RMA (turnaround time of ≤12 h, targeting ≥20 pathogens) and BC. Non-original research articles and animal studies were excluded. The primary outcomes were pooled sensitivity and specificity of RMAs for pathogen detection compared to BC. Bivariate analysis was used to produce summary receiver operating characteristic plots and diagnostic metric measures stratified by different units of analysis (sample versus patient), RMA types, and patient populations. Risk of bias was assessed using the Quality Assessment of Diagnostic Accuracy Studies-2 (QUADAS-2) and Quality Assessment of Diagnostic Accuracy Studies-Comparative (QUADAS-C) tools. The study was registered with PROSPERO, CRD42022377280.

Findings

A total of 63,916 articles were identified, of which 104 were included in the qualitative synthesis and 75 in the quantitative synthesis, covering 17,952 samples and 11,393 patients analyzed separately. Eleven RMAs were identified, with four included in the RMA-based subgroup analysis (LightCycler SeptiFast Test MGRADE®, IRIDICA BAC BSI assay, SepsiTest, MagicPlex Sepsis Test) and five additional ones in the pooled analysis (UMD-SelectNA, VYOO®, MicrobScan assay, MicrobScan-Kairos24/7, REBA Sepsis-ID test). Two RMAs were included in the qualitative synthesis only (InfectID-BSI, Pilot Gene Technology droplet digital polymerase chain reaction). Pooled specificity of RMAs was higher (0.858, 95% confidence interval (CI) 0.830-0.883) than sensitivity (0.659, 95% CI 0.594-0.719) by patient. Sensitivities varied by RMA type from 0.492 (95% CI 0.390-0.594, MagicPlex Sepsis Test) to 0.783 (95% CI 0.662-0.870, IRIDICA BAC BSI assay) by patient. Specificities varied more by patient population, ranging from 0.811 (95% CI 0.716-0.879) in the intensive care population to 0.892 (95% CI 0.838-0.930) in the emergency department population, by patient. Similar metrics were observed when the analysis was done by sample. Risk of bias was judged to be high in all included articles.

Interpretation

Despite their shorter turnaround time, low sensitivity means RMAs cannot replace BCs. However, our data indicate that RMAs may have value as an add-on test by increasing pathogen detection rates. Higher-sensitivity RMAs are needed which could possibly be achieved by expanding pathogen coverage and increasing blood sample volumes. High-quality implementation studies and standardized reporting are required to assess the clinical advantages of RMAs.

Funding

Centre for Translational Medicine, Semmelweis University.

Bacterial DNA detection in very preterm infants assessed for risk of early onset sepsis

OBJECTIVES

The aim of this study is to evaluate the diagnostic ability of multiplex real-time polymerase chain reaction (PCR) in very preterm infants assessed for risk of early onset neonatal sepsis (EOS).

METHODS

Prospective observational cohort study. Blood samples of preterm neonates ≤32 weeks of gestation were evaluated by commercial multiplex real-time PCR within 2 h after delivery. The definition of EOS was based on positive blood culture and clinical signs of infection or negative blood culture, clinical signs of infection and abnormal neonatal blood count and serum biomarkers.

RESULTS

Among 82 subjects analyzed in the study, 15 had clinical or confirmed EOS. PCR was positive in four of these infants (including the only one with a positive blood culture), as well as in 15 of the 67 infants without sepsis (sensitivity 27%, specificity 78%). Out of 19 PCR positive subjects, Escherichia coli was detected in 12 infants (63%). Statistically significant association was found between vaginal E. coli colonization of the mother and E. coli PCR positivity of the neonate (p=0.001). No relationship was found between neonatal E. coli swab results and assessment findings of bacterial DNA in neonatal blood stream.

CONCLUSIONS

Multiplex real-time PCR had insufficient diagnostic capability for EOS in high risk very preterm infants. The study revealed no significant association between PCR results and the diagnosis of clinical EOS. Correlation between maternal vaginal swab results and positive PCR in the newborn needs further investigation to fully understand the role of bacterial DNA analysis in preterm infants.

High-Throughput Two-Dimensional Polymerase Chain Reaction Technology

Polymerase chain reaction (PCR) is a very powerful tool for clinical gene detection. Multiplex PCR especially improves the throughput of this technology. However, it is often necessary to employ techniques such as electrophoresis, mass spectrometry, or sequencing after multiplex PCR amplification for product identification, which requires additional equipment and has high risks of contamination. In this work, we developed a high-throughput two-dimensional (2D) PCR technology that can identify multiple target genes simultaneously in just one closed tube and within a relatively short time by using both fluorescence and the melting temperature (Tm). As an example, a method detecting 9 human papillomavirus (HPV) subtypes and reference genes in a single tube was successfully established using 2D PCR. If designed properly, 2D PCR is believed to have the capability to identify more than 30 genes in one closed tube at a time. This method is particularly suitable for distinguishing microorganisms, single-nucleotide polymorphisms, and the methylation of genes and will be of great help to clinical work.

Progress of electrospray ionization and rapid evaporative ionization mass spectrometric techniques for the broad-range identification of microorganisms

Electrospray ionization and rapid evaporative ionization mass spectrometric techniques have attracted much attention in the identification of microorganisms, and in the diagnosis of bacterial infections from clinical samples.