Cost analysis of real-time polymerase chain reaction microbiological diagnosis in patients with septic shock

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.

Rapid Diagnostic Tests and Antimicrobial Stewardship Programs for the Management of Bloodstream Infection: What Is Their Relative Contribution to Improving Clinical Outcomes? A Systematic Review and Network Meta-analysis

BACKGROUND

Evidence about the clinical impact of rapid diagnostic tests (RDTs) for the diagnosis of bloodstream infections is limited, and whether RDT are superior to conventional blood cultures (BCs) embedded within antimicrobial stewardship programs (ASPs) is unknown.

METHODS

We performed network meta-analyses using results from studies of patients with bloodstream infection with the aim of comparing the clinical impact of RDT (applied on positive BC broth or whole blood) to conventional BC, both assessed with and without ASP with respect to mortality, length of stay (LOS), and time to optimal therapy.

RESULTS

Eighty-eight papers were selected, including 25 682 patient encounters. There was an appreciable amount of statistical heterogeneity within each meta-analysis. The network meta-analyses showed a significant reduction in mortality associated with the use of RDT + ASP versus BC alone (odds ratio [OR], 0.72; 95% confidence interval [CI], .59-.87) and with the use of RDT + ASP versus BC + ASP (OR, 0.78; 95% CI, .63-.96). No benefit in survival was found associated with the use of RDT alone nor with BC + ASP compared to BC alone. A reduction in LOS was associated with RDT + ASP versus BC alone (OR, 0.91; 95% CI, .84-.98) whereas no difference in LOS was shown between any other groups. A reduced time to optimal therapy was shown when RDT + ASP was compared to BC alone (-29 hours; 95% CI, -35 to -23), BC + ASP (-18 hours; 95% CI, -27 to -10), and to RDT alone (-12 hours; 95% CI, -20 to -3).

CONCLUSIONS

The use of RDT + ASP may lead to a survival benefit even when introduced in settings already adopting effective ASP in association with conventional BC.

Hospital-related costs of sepsis around the world: A systematic review exploring the economic burden of sepsis

AIM

The aim of this study was to examine the quality of manuscripts reporting sepsis health care costs and to provide an overview of hospital-related expenditures for sepsis in adult patients around the world.

METHODS

We systematically searched the PubMed, EMBASE, Cochrane and Google Scholar to identify relevant studies between January 2010 and January 2022. We selected articles that provided costs and cost-effectiveness analyses, defined sepsis and described their cost calculation method. All costs were adjusted to 2020 US dollars. Medians and interquartile ranges (IQRs) for various costs of sepsis were calculated. The quality of economic studies was assessed using the Drummond 10-item checklist.

RESULTS

Overall, 26 studies met our eligibility criteria. The mean total hospital costs per patient varied largely, between €1101 and €91,951. The median (IQR) of the total sepsis costs per country were €36,191 (€17,158 - €53,349), which equals €50 (€34 - €84) per capita annually. The relative amount of healthcare budget spent on sepsis was 2.65%, which equals 0.33% of the gross national product (GNP).

CONCLUSION

While general sepsis costs are high, there is considerable variability between countries regarding the costs of sepsis. Further studies examining the impact on sepsis costs, especially on the general ward, can help justify, design and monitor initiatives on prevention, diagnosis, and treatment of this time-critical and potentially preventable disease.

Cost of postoperative sepsis in Vietnam

Despite improvements in medical care, the burden of sepsis remains high. In this study, we evaluated the incremental cost associated with postoperative sepsis and the impact of postoperative sepsis on clinical outcomes among surgical patients in Vietnam. We used the national database that contained 1,241,893 surgical patients undergoing seven types of surgery. We controlled the balance between the groups of patients using propensity score matching method. Generalized gamma regression and logistic regression were utilized to estimate incremental cost, readmission, and reexamination associated with postoperative sepsis. The average incremental cost associated with postoperative sepsis was 724.1 USD (95% CI 553.7-891.7) for the 30 days after surgery, which is equivalent to 28.2% of the per capita GDP in Vietnam in 2018. The highest incremental cost was found in patients undergoing cardiothoracic surgery, at 2,897 USD (95% CI 530.7-5263.2). Postoperative sepsis increased patient odds of readmission (OR = 6.40; 95% CI 6.06-6.76), reexamination (OR = 1.67; 95% CI 1.58-1.76), and also associated with 4.9 days longer of hospital length of stay among surgical patients. Creating appropriate prevention strategies for postoperative sepsis is extremely important, not only to improve the quality of health care but also to save health financial resources each year.

Construction of a non-enzymatic electrochemical sensor based on graphitic carbon nitride nanosheets for sensitive detection of procalcitonin

In this study, we established a label free and ultrasensitive electrochemical sensor based on graphitic nitride nanosheets (g-C₃N₄ NS) for procalcitonin (PCT) detection. Firstly, an easy-to-prepare and well-conducting g-C₃N₄ NS was synthesized. Next the g-C₃N₄ NS was immobilized on the electrode surface by π–π stacking, and further used to anchor the specific recognition peptide (PP). The surface morphology and structure after g-C₃N₄ NS and PP modification was characterized by X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and electrochemistry. The sensing property of this sensor was evaluated by differential pulse voltammetry (DPV) and showed a detection sensitivity with a dynamic range from 0.15 to 11.7 fg mL⁻¹ with a low limit of detection (LOD) of 0.11 fg mL⁻¹. Besides, the electrochemical biosensor was successfully used to detect PCT in human serum samples, and the results suggest its potential use in clinical application.

A simple and ultra-sensitive electrochemical biosensor based on graphitic carbon nitride nanosheets (g-C₃N₄ NS) was developed for the detection of PCT. This sensor presented excellent sensing performance and demonstrates potential for clinical application.

Diagnostic Testing for Sepsis: A Systematic Review of Economic Evaluations

Introduction: Sepsis is a serious and expensive healthcare problem, when caused by a multidrug-resistant (MDR) bacteria mortality and costs increase. A reduction in the time until the start of treatment improves clinical results. The objective is to perform a systematic review of economic evaluations to analyze the cost-effectiveness of diagnostic methods in sepsis and to draw lessons on the methods used to incorporate antimicrobial resistance (AMR) in these studies. Material and Methods: the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were followed, and the Consolidated Health Economic Evaluation Reporting standards (CHEERS) checklist was used to extract the information from the texts. Results: A total of 16 articles were found. A decision model was performed in 14. We found two ways to handle resistance while modelling: the test could identify infections caused by a resistant pathogen or resistance-related inputs, or outcomes were included (the incidence of AMR in sepsis patients, antibiotic use, and infection caused by resistant bacterial pathogens). Conclusion: Using a diagnostic technique to detect sepsis early on is more cost-effective than standard care. Setting a direct relationship between the implementation of a testing strategy and the reduction of AMR cases, we made several assumptions about the efficacy of antibiotics and the length-of-stay of patients.

The Clinical Impact of Rapid Molecular Microbiological Diagnostics for Pathogen and Resistance Gene Identification in Patients With Sepsis: A Systematic Review

Fast microbiological diagnostics (MDx) are needed to ensure early targeted antimicrobial treatment in sepsis. This systematic review focuses on the impact on antimicrobial management and patient outcomes of MDx for pathogen and resistance gene identification compared with blood cultures. PubMed was searched for clinical studies using either whole blood directly or after short-term incubation. Twenty-five articles were retrieved describing the outcomes of 8 different MDx. Three interventional studies showed a significant increase in appropriateness of antimicrobial therapy and a nonsignificant change in time to appropriate therapy. Impact on mortality was conflicting. Length of stay was significantly lower in 2 studies. A significant decrease in antimicrobial cost was demonstrated in 6 studies. The limitations of this systematic review include the low number and observed heterogeneity of clinical studies. In conclusion, potential benefits of MDx regarding antimicrobial management and some patient outcomes were reported. More rigorous intervention studies are needed focusing on the direct benefits for patients.

Health economic evaluations of sepsis interventions in critically ill adult patients: a systematic review

Background

Sepsis is a global health priority. Interventions to reduce the burden of sepsis need to be both effective and cost-effective. We performed a systematic review of the literature on health economic evaluations of sepsis treatments in critically ill adult patients and summarised the evidence for cost-effectiveness.

Methods

We systematically searched MEDLINE, Embase, and the Cochrane Library using thesaurus (e.g. MeSH) and free-text terms related to sepsis and economic evaluations. We included all articles that reported, in any language, an economic evaluation of an intervention for the management of sepsis in critically ill adult patients. Data extracted included study details, intervention details, economic evaluation methodology, and outcomes. Included studies were appraised for reporting quality using the Consolidated Health Economic Evaluation Reporting Standards (CHEERS) checklist.

Results

We identified 50 records representing 46 economic evaluations for a variety of interventions including antibiotics (n = 5), fluid therapy (n = 2), early goal-directed therapy and other resuscitation protocols (n = 8), immunoglobulins (n = 2), and interventions no longer in clinical use such as monoclonal antibodies (n = 7) and drotrecogin alfa (n = 13). Twelve (26%) evaluations were of excellent reporting quality. Incremental cost-effectiveness ratios (ICERs) ranged from dominant (lower costs and higher effectiveness) for early goal-directed therapy, albumin, and a multifaceted sepsis education program to dominated (higher costs and lower effectiveness) for polymerase chain reaction assays (LightCycler SeptiFast testing MGRADE®, SepsiTest™, and IRIDICA BAC BSI assay). ICERs varied widely across evaluations, particularly in subgroup analyses.

Conclusions

There is wide variation in the cost-effectiveness of sepsis interventions. There remain important gaps in the literature, with no economic evaluations identified for several interventions routinely used in sepsis. Given the high economic and social burden of sepsis, high-quality economic evaluations are needed to increase our understanding of the cost-effectiveness of these interventions in routine clinical practice and to inform decision makers.

Trial registration

PROSPERO CRD42018095980

Multiplex polymerase chain reaction to diagnose bloodstream infections in patients after cardiothoracic surgery

Background

Sepsis and other infectious complications are major causes of mortality and morbidity in patients after cardiac surgery. Whereas conventional blood culture (BC) suffers from low sensitivity as well as a reporting delay of approximately 48–72 h, real-time multiplex polymerase chain reaction (PCR) based technologies like “SeptiFast” (SF) might offer a fast and reliable alternative for detection of bloodstream infections (BSI). The aim of this study was to compare the performance of SF with BC testing in patients suspected of having BSI after cardiac surgery.

Methods

Two hundred seventy-nine blood samples from 169 individuals with suspected BSI were analyzed by SF and BC. After excluding results attributable to contaminants, a comparison between the two groups were carried out. Receiver operating characteristic (ROC) curves were generated to determine the accuracy of clinical and laboratory values for the prediction of positive SF results.

Results

14.7% (n = 41) of blood samples were positive using SF and 17.2% (n = 49) using BC (n.s. [p > 0.05]). In six samples SF detected more than one pathogen. Among the 47 microorganisms identified by SF, only 11 (23.4%) could be confirmed by BC. SF identified a higher number of Gram-negative bacteria than BC did (28 vs. 12, χ² = 7.97, p = 0.005). The combination of BC and SF increased the number of detected microorganisms, including fungi, compared to BC alone (86 vs. 49, χ² = 13.51, p < 0.001). C-reactive protein (CRP) (21.7 ± 11.41 vs. 16.0 ± 16.9 mg/dl, p = 0.009), procalcitonin (28.7 ± 70.9 vs. 11.5 ± 30.4 ng/dl, p = 0.015), and interleukin 6 (IL 6) (932.3 ± 1306.7 vs. 313.3 ± 686.6 pg/ml, p = 0.010) plasma concentrations were higher in patients with a positive SF result. Using ROC analysis, IL-6 (AUC 0.836) and CRP (AUC 0.804) showed the best predictive values for positive SF results.

Conclusion

The SF test represent a valuable method for rapid etiologic diagnosis of BSI in patients after cardiothoracic surgery. In particular this method applies for individuals with suspected Gram-negative blood stream. Due to the low performance in detecting Gram-positive pathogens and the inability to determine antibiotic susceptibility, it should be used in addition to BC only (Pilarczyk K, et al., Intensive Care Med Exp ,3(Suppl. 1):A884, 2015).

Evaluation of QuickFISH and maldi Sepsityper for identification of bacteria in bloodstream infection

BACKGROUND

Early detection of bacteria and their antibiotic susceptibility patterns are critical to guide therapeutic decision-making for optimal care of septic patients. The current gold standard, blood culturing followed by subculture on agar plates for subsequent identification, is too slow leading to excessive use of broad-spectrum antibiotic with harmful consequences for the patient and, in the long run, the public health. The aim of the present study was to assess the performance of two commercial assays, QuickFISH® (OpGen) and Maldi Sepsityper™ (Bruker Daltonics) for early and accurate identification of microorganisms directly from positive blood cultures.

MATERIALS AND METHODS

During two substudies of positive blood cultures, the two commercial assays were assessed against the routine method used at the clinical microbiology laboratory, Unilabs AB, at Skaraborg Hospital, Sweden.

RESULTS

The Maldi Sepsityper™ assay enabled earlier microorganism identification. Using the cut-off for definite species identification according to the reference method (>2.0), sufficiently accurate species identification was achieved, but only among Gram-negative bacteria. The QuickFISH^® assay was time-saving and showed high concordance with the reference method, 94.8% (95% CI 88.4-98.3), when the causative agent was covered by the QuickFISH^® assay.

CONCLUSIONS

The use of the commercial assays may shorten the time to identification of causative agents in bloodstream infections and can be a good complement to the current clinical routine diagnostics. Nevertheless, the performance of the commercial assays is considerably affected by the characteristics of the causative agents.

Recent advances in biosensors for diagnosis and detection of sepsis: A comprehensive review

Sepsis is one of the leading causes of mortality among critically ill patients globally. According to WHO report 2018, it is estimated to affect beyond 30 million people worldwide every year. It causes loss of human lives, which arise from infection and inflammation and long term stay in intensive care unit (ICU) in hospitals. Despite the availability of satisfactory prognostic markers contributing to the diagnosis of sepsis, millions of people die even after admission to the hospitals. Correct and early diagnosis of sepsis leads to rapid administration of appropriate antibiotics can thus potentially avert the attainment to critical stages of sepsis, thereby saving human lives. Conventional diagnostic practices are costly, time consuming and they lack adequate sensitivity and selectivity, provoking an urgent need for developing alternate sepsis diagnosis systems. Nevertheless, biosensors have the much-treasured scope for reasonable sepsis diagnosis. Advancement in nano-biotechnology has provided new paradigm for biosensor platforms with upgraded features. Here, we provide an overview of the recent advances in biosensors with a brief introduction to sepsis, followed by the conventional methods of diagnosis and bio-sensing. To conclude, a proactive role and an outlook on technologically advanced biosensor platforms are discoursed with possible biomedical applications.

Sepsis: the LightCycler SeptiFast Test MGRADE®, SepsiTest™ and IRIDICA BAC BSI assay for rapidly identifying bloodstream bacteria and fungi - a systematic review and economic evaluation

BACKGROUND

Sepsis can lead to multiple organ failure and death. Timely and appropriate treatment can reduce in-hospital mortality and morbidity.

OBJECTIVES

To determine the clinical effectiveness and cost-effectiveness of three tests [LightCycler SeptiFast Test MGRADE(®) (Roche Diagnostics, Risch-Rotkreuz, Switzerland); SepsiTest(TM) (Molzym Molecular Diagnostics, Bremen, Germany); and the IRIDICA BAC BSI assay (Abbott Diagnostics, Lake Forest, IL, USA)] for the rapid identification of bloodstream bacteria and fungi in patients with suspected sepsis compared with standard practice (blood culture with or without matrix-absorbed laser desorption/ionisation time-of-flight mass spectrometry).

DATA SOURCES

Thirteen electronic databases (including MEDLINE, EMBASE and The Cochrane Library) were searched from January 2006 to May 2015 and supplemented by hand-searching relevant articles.

REVIEW METHODS

A systematic review and meta-analysis of effectiveness studies were conducted. A review of published economic analyses was undertaken and a de novo health economic model was constructed. A decision tree was used to estimate the costs and quality-adjusted life-years (QALYs) associated with each test; all other parameters were estimated from published sources. The model was populated with evidence from the systematic review or individual studies, if this was considered more appropriate (base case 1). In a secondary analysis, estimates (based on experience and opinion) from seven clinicians regarding the benefits of earlier test results were sought (base case 2). A NHS and Personal Social Services perspective was taken, and costs and benefits were discounted at 3.5% per annum. Scenario analyses were used to assess uncertainty.

RESULTS

For the review of diagnostic test accuracy, 62 studies of varying methodological quality were included. A meta-analysis of 54 studies comparing SeptiFast with blood culture found that SeptiFast had an estimated summary specificity of 0.86 [95% credible interval (CrI) 0.84 to 0.89] and sensitivity of 0.65 (95% CrI 0.60 to 0.71). Four studies comparing SepsiTest with blood culture found that SepsiTest had an estimated summary specificity of 0.86 (95% CrI 0.78 to 0.92) and sensitivity of 0.48 (95% CrI 0.21 to 0.74), and four studies comparing IRIDICA with blood culture found that IRIDICA had an estimated summary specificity of 0.84 (95% CrI 0.71 to 0.92) and sensitivity of 0.81 (95% CrI 0.69 to 0.90). Owing to the deficiencies in study quality for all interventions, diagnostic accuracy data should be treated with caution. No randomised clinical trial evidence was identified that indicated that any of the tests significantly improved key patient outcomes, such as mortality or duration in an intensive care unit or hospital. Base case 1 estimated that none of the three tests provided a benefit to patients compared with standard practice and thus all tests were dominated. In contrast, in base case 2 it was estimated that all cost per QALY-gained values were below £20,000; the IRIDICA BAC BSI assay had the highest estimated incremental net benefit, but results from base case 2 should be treated with caution as these are not evidence based.

LIMITATIONS

Robust data to accurately assess the clinical effectiveness and cost-effectiveness of the interventions are currently unavailable.

CONCLUSIONS

The clinical effectiveness and cost-effectiveness of the interventions cannot be reliably determined with the current evidence base. Appropriate studies, which allow information from the tests to be implemented in clinical practice, are required.

STUDY REGISTRATION

This study is registered as PROSPERO CRD42015016724.

FUNDING

The National Institute for Health Research Health Technology Assessment programme.

Performance and economic evaluation of the molecular detection of pathogens for patients with severe infections: the EVAMICA open-label, cluster-randomised, interventional crossover trial

PURPOSE

Microbiological diagnosis (MD) of infections remains insufficient. The resulting empirical antimicrobial therapy leads to multidrug resistance and inappropriate treatments. We therefore evaluated the cost-effectiveness of direct molecular detection of pathogens in blood for patients with severe sepsis (SES), febrile neutropenia (FN) and suspected infective endocarditis (SIE).

METHODS

Patients were enrolled in a multicentre, open-label, cluster-randomised crossover trial conducted during two consecutive periods, randomly assigned as control period (CP; standard diagnostic workup) or intervention period (IP; additional testing with LightCycler®SeptiFast). Multilevel models used to account for clustering were stratified by clinical setting (SES, FN, SIE).

RESULTS

A total of 1416 patients (907 SES, 440 FN, 69 SIE) were evaluated for the primary endpoint (rate of blood MD). For SES patients, the MD rate was higher during IP than during CP [42.6% (198/465) vs. 28.1% (125/442), odds ratio (OR) 1.89, 95% confidence interval (CI) 1.43-2.50; P < 0.001], with an absolute increase of 14.5% (95% CI 8.4-20.7). A trend towards an association was observed for SIE [35.4% (17/48) vs. 9.5% (2/21); OR 6.22 (0.98-39.6)], but not for FN [32.1% (70/218) vs. 30.2% (67/222), P = 0.66]. Overall, turn-around time was shorter during IP than during CP (22.9 vs. 49.5 h, P < 0.001) and hospital costs were similar (median, mean ± SD: IP €14,826, €18,118 ± 17,775; CP €17,828, €18,653 ± 15,966). Bootstrap analysis of the incremental cost-effectiveness ratio showed weak dominance of intervention in SES patients.

CONCLUSION

Addition of molecular detection to standard care improves MD and thus efficiency of healthcare resource usage in patients with SES. ClinicalTrials.gov registration number: NCT00709358.

Molecular diagnosis of bloodstream infections in onco-haematology patients with PCR/ESI-MS technology

OBJECTIVES

Onco-haematological patients are prone to develop infections, and antibiotic prophylaxis may lead to negative blood cultures. Thus, the microbiological diagnosis and subsequent administration of a targeted antimicrobial therapy is often difficult. The goal of this study was to evaluate the usefulness of IRIDICA (PCR/ESI-MS technology) for the molecular diagnosis of bloodstream infections in this patient group.

METHODS

A total of 463 whole blood specimens from different sepsis episodes in 429 patients were analysed using the PCR/ESI-MS platform, comparing the results with those of blood culture and other clinically relevant information.

RESULTS

The sensitivity of PCR/ESI-MS by specimen (excluding polymicrobial infections, n = 25) in comparison with blood culture was 64.3% overall, 69.0% in oncological patients, and 59.3% in haematological patients. When comparing with a clinical infection criterion, overall sensitivity rose to 74.7%, being higher in oncological patients (80.0%) than in haematological patients (67.7%). Thirty-one microorganisms isolated by culture were not detected by IRIDICA, whereas 42 clinically relevant pathogens not isolated by culture were detected moleculary.

CONCLUSIONS

PCR/ESI-MS offers a reliable identification of pathogens directly from whole blood. While additional studies are needed to confirm our findings, the system showed a lower sensitivity in onco-haematological patients in comparison with previously reported results in patients from the Intensive Care Unit.

Hospital-related cost of sepsis: A systematic review

OBJECTIVES

This article systematically reviews research on the costs of sepsis and, as a secondary aim, evaluates the quality of economic evaluations reported in peer-reviewed journals.

METHODS

We systematically searched the MEDLINE, National Health Service (Abstracts of Reviews of Effects, Economic Evaluation and Health Technology Assessment), Cost-effectiveness Analysis Registry and Web of Knowledge databases for studies published between January 2005 and June 2015. We selected original articles that provided cost and cost-effectiveness analyses, defined sepsis and described their cost calculation method. Only studies that considered index admissions and re-admissions in the first 30 days were published in peer-reviewed journals and used standard treatments were considered. All costs were adjusted to 2014 US dollars. Medians and interquartile ranges (IQRs) for various costs of sepsis were calculated. The quality of economic studies was assessed using the Drummond 10-item checklist.

RESULTS

Overall, 37 studies met our eligibility criteria. The median of the mean hospital-wide cost of sepsis per patient was $32,421 (IQR $20,745-$40,835), and the median of the mean ICU cost of sepsis per patient was $27,461 (IQR $16,007-$31,251). Overall, the quality of economic studies was low.

CONCLUSIONS

Estimates of the hospital-related costs of sepsis varied considerably across the included studies depending on the method used for cost calculation, the type of sepsis and the population that was examined. A standard model for conducting cost improve the quality of studies on the costs of sepsis.

Emerging methodologies for pathogen identification in positive blood culture testing

Bloodstream infections (BSIs) represent a major cause of death in developed countries and are associated with long-term loss of functions. Blood culture remains the gold standard for BSI diagnosis, as it is easy to perform and displays a good analytical sensitivity. However, its major drawback remains the long turnaround time, which can result in inappropriate therapy, fall of survival rate, emergence of antibiotic resistance and increase of medical costs. Over the last 10 years, molecular tools have been the alternative to blood cultures, allowing early identification of pathogens involved in sepsis, as well detection of critical antibiotic resistance genes. Besides, the advent of MALDI-TOF revolutionized practice in routine microbiology significantly reduced the time to result. Reviewed here are recent improvements in early BSI diagnosis and these authors' view for the future is presented, including innovative high-throughput technologies.

Evaluation of the Broad-Range PCR/ESI-MS Technology in Blood Specimens for the Molecular Diagnosis of Bloodstream Infections

BACKGROUND

Rapid identification of the etiological agent in bloodstream infections is of vital importance for the early administration of the most appropriate antibiotic therapy. Molecular methods may offer an advantage to current culture-based microbiological diagnosis. The goal of this study was to evaluate the performance of IRIDICA, a platform based on universal genetic amplification followed by mass spectrometry (PCR/ESI-MS) for the molecular diagnosis of sepsis-related pathogens directly from the patient's blood.

METHODS

A total of 410 whole blood specimens from patients admitted to Emergency Room (ER) and Intensive Care Unit (ICU) with clinical suspicion of sepsis were tested with the IRIDICA BAC BSI Assay (broad identification of bacteria and Candida spp.). Microorganisms grown in culture and detected by IRIDICA were compared considering blood culture as gold standard. When discrepancies were found, clinical records and results from other cultures were taken into consideration (clinical infection criterion).

RESULTS

The overall positive and negative agreement of IRIDICA with blood culture in the analysis by specimen was 74.8% and 78.6%, respectively, rising to 76.9% and 87.2% respectively, when compared with the clinical infection criterion. Interestingly, IRIDICA detected 41 clinically significant microorganisms missed by culture, most of them from patients under antimicrobial treatment. Of special interest were the detections of one Mycoplasma hominis and two Mycobacterium simiae in immunocompromised patients. When ICU patients were analyzed separately, sensitivity, specificity, positive and negative predictive values compared with blood culture were 83.3%, 78.6%, 33.9% and 97.3% respectively, and 90.5%, 87.2%, 64.4% and 97.3% respectively, in comparison with the clinical infection criterion.

CONCLUSIONS

IRIDICA is a promising technology that offers an early and reliable identification of a wide variety of pathogens directly from the patient's blood within 6h, which brings the opportunity to improve management of septic patients, especially for those critically ill admitted to the ICU.

Rapid molecular diagnostic tests in patients with bacteremia: evaluation of their impact on decision making and clinical outcomes

We performed a systematic review of the data regarding rapid diagnostic tests and their advantages or limitations on patients' clinical outcomes. The PubMed and Scopus databases were searched independently by two reviewers. Mortality was the primary outcome. Most studies compared rapid tests with blood cultures. Although not observed in all studies, only studies comparing rapid tests in conjunction with antimicrobial stewardship programs (ASPs) showed a mortality benefit. A reduction in hospital or intensive care unit (ICU) length of stay was also observed in almost all studies when the rapid tests, with or without ASPs, were used. Finally, treatment decisions were taken earlier in the rapid test groups. Despite a faster treatment decision, a clear mortality benefit was not seen when rapid tests were used. It is crucial to differentiate the influence of rapid tests from that of ASPs and clarify the actual effect of each factor separately.

Emerging commercial molecular tests for the diagnosis of bloodstream infection

Bloodstream infection (BSI) by microorganisms can lead to sepsis. This condition has a high mortality rate, which rises significantly with delays in initiation of appropriate antimicrobial treatment. Current culture methods for diagnosing BSI have long turnaround times and poor clinical sensitivity. While clinicians wait for culture diagnosis, patients are treated empirically, which can result in inappropriate treatment, undesirable side effects and contribute to drug resistance development. Molecular diagnostics assays that target pathogen DNA can identify pathogens and resistance markers within hours. Early diagnosis improves antibiotic stewardship and is associated with favorable clinical outcomes. Nonetheless, limitations of current molecular diagnostic methods are substantial. This article reviews recent commercially available molecular methods that use pathogen DNA to diagnose BSI, either by testing positive blood cultures or directly testing patient blood. We critically assess these tests and their application in clinical microbiology. A view of future directions in BSI diagnosis is also provided.

Direct molecular detection of pathogens in blood as specific rule-in diagnostic biomarker in patients with presumed sepsis: our experience on a heterogeneous cohort of patients with signs of infective systemic inflammatory response syndrome

The practical value of blood cultures in the diagnosis of sepsis is impaired by a delay in the turnaround time to result and by the fact that blood culture positive can be found for only about 30% of these patients. Conventional laboratory signs of sepsis and acute phase protein biomarkers are sensitive and easy to use, but often also very nonspecific. Molecular diagnostic reflects currently the most promising avenue to decrease time to result and to influence decision making for antibiotic therapy in the septic host. In this study, we wish to highlight the impact of the LightCycler SeptiFast, a multipathogen probe-based real-time polymerase chain reaction, in the rapid etiological diagnosis of sepsis in patients with clinical and laboratory signs of bloodstream infections. We have evaluated prospectively 830 adult patients with suspected bloodstream infection and at least two criteria of systemic inflammatory response syndrome. In more than 50% of critically ill patients strongly suspected of having sepsis, we arrived to an etiological diagnosis only by the molecular method in a median time of 15 h, with specificity and predictive positive values of 96% and 94%, respectively. We highlight the role of DNAemia as time-critical, high-specificity, etiological, non-culture-based rule-in diagnostic biomarker in patients with presumed sepsis.

Multiplex PCR performed of bronchoalveolar lavage fluid increases pathogen identification rate in critically ill patients with pneumonia: a pilot study

Background

In critically ill patients with pneumonia, accurate microorganism identification allows appropriate antibiotic treatment. In patients undergoing bronchoalveolar lavage (BAL), direct examination of the fluid using Gram staining provides prompt information but pathogen identification accuracy is low. Culture of BAL fluid is actually the reference, but it is not available before 24 to 48 h. In addition, pathogen identification rate observed with direct examination and culture is decreased when antibiotic therapy has been given prior to sampling. We therefore assessed, in critically ill patients with suspected pneumonia, the performance of a multiplex PCR (MPCR) to identify pathogens in BAL fluid. This study is a prospective pilot observation.

Methods

We used a MPCR detecting 20 types of microorganisms. Direct examination, culture, and MPCR were performed on BAL fluid of critically ill patients with pneumonia suspicion. The final diagnosis of infective pneumonia was retained after the medical chart was reviewed by two experts. Pathogen identification rate of direct examination, culture, and MPCR in patients with confirmed pneumonia was compared.

Results

Among the 65 patients with pneumonia suspicion, the diagnosis of pneumonia was finally retained in 53 cases. Twenty nine (55%) were community-acquired pneumonia and 24 (45%) were hospital acquired. Pathogen identification rate with MPCR (66%) was greater than with culture (40%) and direct examination (23%) (p =0.01 and p <0.001, respectively). When considering only the microorganisms included in the MPCR panel, the pathogen identification rate provided by MPCR reached 82% and was still higher than with culture (35%, p <0.001) and direct examination (21%, p <0.001). Pathogen identification rate provided by MPCR was not modified in the case of previous antibiotic treatment (66% vs. 64%, NS) and was still better than with culture (23%, p <0.001).

Conclusions

The results of this pilot study suggest that in critically ill patients, MPCR performed on BAL fluid could provide higher identification rate of pathogens involved in pneumonia than direct examination and culture, especially in patients having received antimicrobial treatment.

Quantitative data from the SeptiFast real-time PCR is associated with disease severity in patients with sepsis

Background

The commercial test, SeptiFast, is designed to detect DNA from bacterial and fungal pathogens in whole blood. The method has been found to be specific with a high rule-in value for the early detection of septic patients. The software automatically provides information about the identified pathogen, without quantification of the pathogen. However, it is possible to manually derive Crossing point (Cp) values, i.e. the PCR cycle at which DNA is significantly amplified. The aim of this study was to find out whether Cp values correlate to disease severity.

Methods

We used a study cohort of patients with positive results from SeptiFast tests for bacteria from a recent study which included patients with suspected sepsis in the Emergency department. Cp values were compared with disease severity, classified as severe sepsis/septic shock or non-severe sepsis, according to the criteria of the American College of Chest Physicians/Society of Critical Care Medicine.

Results

Ninety-four patients were included. The prevalence of severe sepsis/septic shock in the study was 29%. SeptiFast positive tests from patients with severe sepsis/septic shock had significantly lower Cp values compared with those from patients with non-severe sepsis, median 16.9 (range: 7.3 - 24.3) versus 20.9 (range: 8.5 - 25.0), p < 0.001. Positive predictive values from the SeptiFast test for identifying severe sepsis/septic shock were 34% at Cp cut-off <25.0, 35% at Cp cut-off <22.5, 50% at Cp cut-off <20.0, and 73% at Cp cut-off <17.5. Patients with a positive Septifast test with a Cp value <17.5 had significantly more severe sepsis/septic shock (73% versus 15%, p < 0.001), were more often admitted to the Intensive Care Unit (23% versus 4%, p = 0.016), had positive blood culture (BC) more frequently (100% versus 32%, p < 0.001) and had longer hospital stays (median 19.5 [range: 4 - 78] days versus 5 [range: 0 - 75] days, p < 0.001) compared with those with a Cp value >17.5.

Conclusions

Our results suggest that introducing quantitative data to the SeptiFast test could be of value in assessing sepsis severity. Moreover, such data might also be useful in predicting a positive BC result.

Molecular diagnosis of sepsis: New aspects and recent developments

By shortening the time to pathogen identification and allowing for detection of organisms missed by blood culture, new molecular methods may provide clinical benefits for the management of patients with sepsis. While a number of reviews on the diagnosis of sepsis have recently been published we here present up-to-date new developments including multiplex PCR, mass spectrometry and array techniques. We focus on those techniques that are commercially available and for which clinical studies have been performed and published.

Rapid diagnosis of bloodstream infections with PCR followed by mass spectrometry

Achieving a rapid microbiological diagnosis is crucial for decreasing morbidity and mortality of patients with a bloodstream infection, as it leads to the administration of an appropriate empiric antimicrobial therapy. Molecular methods may offer a rapid alternative to conventional microbiological diagnosis involving blood culture. In this study, the performance of a new technology that uses broad-spectrum PCR coupled with mass spectrometry (PCR/ESI-MS) was evaluated for the detection of microorganisms directly from whole blood. A total of 247 whole blood samples and paired blood cultures were prospectively obtained from 175 patients with a suspicion of sepsis. Both sample types were analyzed using the PCR/ESI-MS technology, and the results were compared with those obtained by conventional identification methods. The overall agreement between conventional methods and PCR/ESI-MS performed in blood culture aliquots was 94.2% with 96.8% sensitivity and 98.5% specificity for the molecular method. When comparing conventional methods with PCR/ESI-MS performed in whole blood specimens, the overall agreement was 77.1% with 50% sensitivity and 93.8% specificity for the molecular method. Interestingly, the PCR/ESI-MS technology led to the additional identification of 13 pathogens that were not found by conventional methods. Using the PCR/ESI-MS technology the microbiological diagnosis of bloodstream infections could be anticipated in about half of the patients in our setting, including a small but significant proportion of patients newly diagnosed. Thus, this promising technology could be very useful for the rapid diagnosis of sepsis in combination with traditional methods.

Revolutionising bacteriology to improve treatment outcomes and antibiotic stewardship

Laboratory investigation of bacterial infections generally takes two days: one to grow the bacteria and another to identify them and to test their susceptibility. Meanwhile the patient is treated empirically, based on likely pathogens and local resistance rates. Many patients are over-treated to prevent under-treatment of a few, compromising antibiotic stewardship. Molecular diagnostics have potential to improve this situation by accelerating precise diagnoses and the early refinement of antibiotic therapy. They include: (i) the use of 'biomarkers' to swiftly distinguish patients with bacterial infection, and (ii) molecular bacteriology to identify pathogens and their resistance genes in clinical specimens, without culture. Biomarker interest centres on procalcitonin, which has given good results particularly for pneumonias, though broader biomarker arrays may prove superior in the future. PCRs already are widely used to diagnose a few infections (e.g. tuberculosis) whilst multiplexes are becoming available for bacteraemia, pneumonia and gastrointestinal infection. These detect likely pathogens, but are not comprehensive, particularly for resistance genes; there is also the challenge of linking pathogens and resistance genes when multiple organisms are present in a sample. Next-generation sequencing offers more comprehensive profiling, but obstacles include sensitivity when the bacterial load is low, as in bacteraemia, and the imperfect correlation of genotype and phenotype. In short, rapid molecular bacteriology presents great potential to improve patient treatments and antibiotic stewardship but faces many technical challenges; moreover it runs counter to the current nostrum of defining resistance in pharmacodynamic terms, rather than by the presence of a mechanism, and the policy of centralising bacteriology services.