Rapid diagnostic methods in the detection of sepsis

A nomogram to predict nosocomial infection in patients on venoarterial extracorporeal membrane oxygenation after cardiac surgery

INTRODUCTION

After cardiac surgery, patients on venoarterial extracorporeal membrane oxygenation (VA-ECMO) have a higher risk of nosocomial infection in the intensive care unit (ICU). We aimed to establish an intuitive nomogram to predict the probability of nosocomial infection in patients on VA-ECMO after cardiac surgery.

METHODS

We included patients on VA-ECMO after cardiac surgery between January 2011 and December 2020 at a single center. We developed a nomogram based on independent predictors identified using univariate and multivariate logistic regression analyses. We selected the optimal model and assessed its performance through internal validation and decision-curve analyses.

RESULTS

Overall, 503 patients were included; 363 and 140 patients were randomly divided into development and validation sets, respectively. Independent predictors derived from the development set to predict nosocomial infection included older age, white blood cell (WBC) count abnormality, ECMO environment in the ICU, and mechanical ventilation (MV) duration, which were entered into the model to create the nomogram. The model showed good discrimination, with areas under the curve (95% confidence interval) of 0.743 (0.692-0.794) in the development set and 0.732 (0.643-0.820) in the validation set. The optimal cutoff probability of the model was 0.457 in the development set (sensitivity, 0.683; specificity, 0.719). The model showed qualified calibration in both the development and validation sets (Hosmer-Lemeshow test, p > .05). The threshold probabilities ranged from 0.20 to 0.70.

CONCLUSIONS

For adult patients receiving VA-ECMO treatment after cardiac surgery, a nomogram-monitoring tool could be used in clinical practice to identify patients with high-risk nosocomial infections and provide an early warning.

Diagnostic Accuracy of Various Biomarkers of Sepsis (Serum Pro-Calcitonin, High-Sensitivity C-reactive Protein, and C-reactive Protein) and Band Cell Percentage in Critically lll Patients: A Prospective, Observational, Cohort Study

Background:

Despite the advances in medical sciences, the morbidity and mortality due to sepsis in critically ill medical or surgical patients remains high, hence the need for an early and accurate diagnosis. In the current armamentarium, we have various biomarkers such as procalcitonin (PCT), high-sensitivity C-reactive protein (hs-CRP), CRP, and band cell percentage for an early clue.

Aims:

This study explores the accuracy of these markers in distinguishing sepsis from systemic inflammatory response syndrome (SIRS) and their correlation with sequential organ failure assessment (SOFA) scoring in critically ill patients.

Materials and Methods:

After ethical committee approval and written informed consent from guardians, 180 consecutive patients, with clinically suspected infection from any source fulfilling at least two criteria of SIRS, were enrolled and 150 eligible patients were investigated and analyzed prospectively in one cohort, which was later subdivided into two different groups (Group A and Group B) based on microbiology reports, as having SIRS or sepsis, respectively. Samples for cultures (blood, tracheal, or urine as required), biomarkers such as PCT, hs-CRP, and CRP, and band cell percentage were sent from each patient on days 1, 2, 3, and 5 and whenever there were fever spikes. Clinical follow-up was done for 28 days, and demographics, ventilator days, duration of intensive care unit (ICU) stay, and the survival rates were noted.

Statistical Analysis:

Receiver operating characteristics, area under curve (AUC-ROC) was used for each of the biomarker variables to decide the cutoff values and performance. Correlation coefficient was also seen for each of the biomarkers with SOFA scoring.

Results:

Attributes of performance for all the biomarkers were satisfactory but was best for PCT (AUC-ROC of 0.987) followed by band cell percentage (0.881). SOFA scoring could also be used with good diagnostic accuracy (AUC-ROC of 0.920). SOFA score correlated best with PCT among the four biomarkers in diagnosing sepsis (Spearman's coefficient of + 0.734). Band cell percentage was significantly higher in the expired group of sepsis patients than survived patients (P = 0.02) and correlated well with ICU stay and 28-day mortality than rest (Spearman's coefficient of − 0.54).

Conclusions:

The addition of PCT to the standard workup of critically ill patients with suspected sepsis increases diagnostic certainty and generates improved patient management. Band cell percentage also provides a cost-effective alternative to PCT with an analogous diagnostic performance.

Prognostic Value of Serially Estimated Serum Procalcitonin Levels in Traumatic Brain Injury Patients With or Without Extra Cranial Injury on Early In-hospital Mortality: A Longitudinal Observational Study

Background

Traumatic brain injury (TBI) is associated with majority of trauma deaths, and objective tools are required to understand the severity of injury. The application of a biomarker like procalcitonin (PCT) in TBI may allow for assessment of severity and thus aid in prognostication and correlation with mortality and outcome.

Aims

The primary objective is to determine the correlation between PCT concentrations with TBI outcomes (mainly in terms of mortality) at intensive care unit (ICU)/hospital discharge. Secondary objectives are to evaluate correlation with associated extra cranial injuries and complications during hospital stay.

Methods

In total, 186 TBI patients aged > 18 years with minimum survival for at least 12 h admitted to the ICU at the level 1 trauma center were prospectively included in the study and divided into two groups: TBI with and without extra cranial injuries. All admitted patients were treated according to the standard institutional protocol. The PCT levels were obtained on admission, on day 2, and 5. Clinical, laboratory, diagnostic, and therapeutic data were also collected. Primary mortality is defined as death related to central nervous system (CNS) injury, while secondary mortality defined as death related to sepsis or extracranial cause.

Results

Median PCT levels at admission, day 2, and day 5 in TBI patients with extracranial injuries were 3.0, 0.83, and 0.69 ng/ml. In total, primary mortality was observed in 18 (9.7%) patients, while secondary causes were attributable in 20 (12.3%) patients. Regression analysis for primarily CNS cause of mortality showed PCT cutoff level at admission more than 5.5 ng/ml carried sensitivity and specificity of 75%, but for secondary cause (sepsis) of mortality, PCT cutoff values on day 2 > 1.15 ng/ml were derived significant with sensitivity of 70% and specificity of 66%. No significant association of parameters like length of ICU stay, Glasgow outcome scale (GOS), and primary/secondary mortality with the presence of extracranial injuries in TBI patients as compared with TBI alone was noted.

Conclusion

This observational study demonstrates the poor correlation between PCT concentrations with outcome at days 1, 2, and 5 post-injury. The predicted relationship between PCT levels and outcome was not confirmed, and that these results do not support the prognostic utility of PCT biomarker in this population for outcome (mortality) assessment in TBI patients with or without extracranial injuries.

Sepsis and ECMO

Sepsis is being recognized as an important complication of extracorporeal membrane oxygenation (ECMO) and its presence is a poor prognostic marker and increases the overall mortality. The survival rate differs in the various types of cannulation techniques. Adult patients with prolonged duration of ECMO constitute the major risk population. Ventilator-associated pneumonia and bloodstream infections form the main sources of sepsis in these patients. It is important to know the most common etiological agents for sepsis in ECMO, which varies partly with the local epidemiology of the hospitals. A high index of suspicion, drawing adequate volumes for blood culture and early and timely administration of appropriate empirical antimicrobials can substantially decrease the morbidity and mortality in this high-risk population. The dosing of antimicrobials is influenced by the pharmacological variations on ECMO machine and is an important consideration. Infection control practices are of paramount importance and need to be followed meticulously to prevent sepsis in ECMO.

Cost-Effectiveness Analysis of a Procalcitonin-Guided Decision Algorithm for Antibiotic Stewardship Using Real-World U.S. Hospital Data

Medical decision-making is revolutionizing with the introduction of artificial intelligence and machine learning. Yet, traditional algorithms using biomarkers to optimize drug treatment continue to be important and necessary. In this context, early diagnosis and rational antimicrobial therapy of sepsis and lower respiratory tract infections (LRTI) are vital to prevent morbidity and mortality. In this study we report an original cost-effectiveness analysis (CEA) of using a procalcitonin (PCT)-based decision algorithm to guide antibiotic prescription for hospitalized sepsis and LRTI patients versus standard care. We conducted a CEA using a decision-tree model before and after the implementation of PCT-guided antibiotic stewardship (ABS) using real-world U.S. hospital-specific data. The CEA included societal and hospital perspectives with the time horizon covering the length of hospital stay. The main outcomes were average total costs per patient, and numbers of patients with Clostridium difficile and antibiotic resistance (ABR) infections. We found that health care with the PCT decision algorithm for hospitalized sepsis and LRTI patients resulted in shorter length of stay, reduced antibiotic use, fewer mechanical ventilation days, and lower numbers of patients with C. difficile and ABR infections. The PCT-guided health care resulted in cost savings of $25,611 (49% reduction from standard care) for sepsis and $3630 (23% reduction) for LRTI, on average per patient. In conclusion, the PCT decision algorithm for ABS in sepsis and LRTI might offer cost savings in comparison with standard care in a U.S. hospital context. To the best of our knowledge, this is the first health economic analysis on PCT implementation using U.S. real-world data. We suggest that future CEA studies in other U.S. and worldwide settings are warranted in the current age when PCT and other decision algorithms are increasingly deployed in precision therapeutics and evidence-based medicine.

Impact of Nasopharyngeal FilmArray Respiratory Panel Results on Antimicrobial Decisions in Hospitalized Patients

Objective

To determine whether results of the nasopharyngeal FilmArray respiratory panel (NP-FARP) influenced antibiotic decisions.

Methods

We reviewed the medical records of nonintensive care unit (ICU) inpatients that had an NP-FARP performed at our institution between June 2013 and June 2014. The inpatient records were reviewed 48 hours after the NP-FARP for the following data: demographic information; NP-FARP, serum procalcitonin, and methicillin-resistant Staphylococcus aureus nasal swab (MRSA NS) results; antibiotics prior and post-48 hours of the NP-FARP result; and the current immunosuppression status. Clinical outcome data were not obtained. Patients were categorized into those who had a positive (+) or a negative (-) NP-FARP. We further subdivided these two categories into groups A, B, and C based on the antibiotic modifications 48 hours after their NP-FARP result. Group A included patients who were never initiated on antimicrobial therapy. Patients whose antibiotics were discontinued or deescalated were placed in group B. Patients with antibiotic escalation or continuation without change constituted group C. We compared and analyzed groups A, B, and C in the (+) and (-) NP-FARP cohorts.

Results

A total of 545 patients were included. There were 143 (26%) patients with positive and 402 (74%) patients with negative NP-FARPs. Comparison of groups A, B, and C between those with a (+) and (-) NP-FARP were as follows: (+) A and (-) A, 28/143 (20%) and 84/402 (21%); (+) B and (-) B, 59/143 (41%) and 147/402 (37%); and (+) C and (-) C, 56/143 (39%) and 171/402 (43%), respectively. We found no statistically significant differences between groups (+) A versus (-) A, (+) B versus (-) B, and (+) C versus (-) C with respect to age, gender, MRSA NS result, procalcitonin result, or concurrent immunosuppression.

Conclusion

In non-ICU inpatients, NP-FARP alone or in combination with procalcitonin or MRSA NS did not influence antibiotic decisions during the study period.

Infectious complications in paediatric patients treated with extracorporeal membrane oxygenation

INTRODUCTION

The aim of this study was to analyse the incidence, treatment and evolution of infections in children treated with ECMO.

METHODS

A retrospective study based on a prospective database was performed. Children under the age of 18 years treated with ECMO from September 2006 to November 2015 were included. The patients' clinical characteristics were collected, together with ECMO technique, cultures and treatment of infection.

RESULTS

One hundred patients with a median age of 11 months were analysed. Heart disease was diagnosed in 94 patients. An infection was suspected and antibiotic treatment was initiated in 51 patients, although only 22 of them were microbiologically confirmed. The most common infection was sepsis (49%), followed by pneumonia (35.3%) and urinary tract infection (9.8%). There were no differences in haematological parameters and acute phase reactants between children with infection and those without. Children who died had a higher incidence of infection during ECMO (60.4%) than the survivors (40.3%), but the difference did not reach statistical significance (P=.07). The duration of admission in the PICU was 57 days in patients with infection vs 37 days in patients without infection but the difference was not statistically significant (P=.067).

CONCLUSIONS

Infection in children with ECMO is common. There are no specific infection parameters and less than half of the clinical infections are confirmed microbiologically. There was no statistically significant correlation between infection and mortality or duration of PICU stay.

Rapid Detection of Bacteria from Blood with Surface-Enhanced Raman Spectroscopy

Traditional methods for identifying pathogens in bacteremic patients are slow (24-48+ h). This can lead to physicians making treatment decisions based on an incomplete diagnosis and potentially increasing the patient's mortality risk. To decrease time to diagnosis, we have developed a novel technology that can recover viable bacteria directly from whole blood and identify them in less than 7 h. Our technology combines a sample preparation process with surface-enhanced Raman spectroscopy (SERS). The sample preparation process enriches viable microorganisms from 10 mL of whole blood into a 200 μL aliquot. After a short incubation period, SERS is used to identify the microorganisms. We further demonstrated that SERS can be used as a broad detection method, as it identified a model set of 17 clinical blood culture isolates and microbial reference strains with 100% identification agreement. By applying the integrated technology of sample preparation and SERS to spiked whole blood samples, we were able to correctly identify both Staphylococcus aureus and Escherichia coli 97% of the time with 97% specificity and 88% sensitivity.

Procalcitonin as a biomarker of bacterial infection in pediatric patients after congenital heart surgery

Background:

Bacterial infection (BI) after congenital heart surgery (CHS) is associated with increased morbidity and is difficult to differentiate from systemic inflammatory response syndrome caused by cardiopulmonary bypass (CPB). Procalcitonin (PCT) has emerged as a reliable biomarker of BI in various populations.

Aim:

To determine the optimal PCT threshold to identify BI among children suspected of having infection following CPB.

Setting and Design:

Single-center retrospective observational study.

Materials and Methods:

Medical records of all the patients admitted between January 2013 and April 2015 were reviewed. Patients in the age range of 0-21 years of age who underwent CHS requiring CPB in whom PCT was drawn between postoperative days 0-8 due to suspicion of infection were included.

Statistical Analysis:

The Wilcoxon rank-sum test was used for nonparametric variables. The diagnostic performance of PCT was evaluated using a receiver operating characteristic (ROC) curve.

Results:

Ninety-eight patients were included. The median age was 2 months (25th and 75th interquartile of 0.1-7.5 months). Eleven patients were included in the BI group. The median PCT for the BI group (3.42 ng/mL, 25th and 75th interquartile of 2.34-5.67) was significantly higher than the median PCT for the noninfected group (0.8 ng/mL, 25th and 75th interquartile 0.38-3.39), P = 0.028. The PCT level that yielded the best compromise between the sensitivity (81.8%) and specificity (66.7%) was 2 ng/mL with an area under the ROC curve of 0.742.

Conclusion:

A PCT less than 2 ng/mL makes BI unlikely in children suspected of infection after CHS.

Diagnostic Accuracy of Lipopolysaccharide-Binding Protein as Biomarker for Sepsis in Adult Patients: A Systematic Review and Meta-Analysis

INTRODUCTION

Lipopolysaccharide-binding protein (LBP) is widely reported as a biomarker to differentiate infected from non-infected patients. The diagnostic use of LBP for sepsis remains a matter of debate. We aimed to perform a systematic review and meta-analysis to assess the diagnostic accuracy of serum LBP for sepsis in adult patients.

METHODS

We performed a systematic review and meta-analysis to assess the accuracy of LBP for sepsis diagnosis. A systematic search in PubMed and EMBASE for studies that evaluated the diagnostic role of LBP for sepsis through December 2015 was conducted. We searched these databases for original, English language, research articles that studied the diagnostic accuracy between septic and non-septic adult patients. Sensitivity, specificity, and other measures of accuracy, such as diagnostic odds ratio (DOR) and area under the receiver operating characteristic curve (AUC) of LBP were pooled using the Hierarchical Summary Receiver Operating Characteristic (HSROC) method.

RESULTS

Our search returned 53 reports, of which 8 fulfilled the inclusion criteria, accounting for 1684 patients. The pooled sensitivity and specificity of LBP for diagnosis of sepsis by the HSROC method were 0.64 (95% CI: 0.56-0.72) and 0.63 (95% CI: 0.53-0.73), respectively. The value of the DOR was 3.0 (95% CI: 2.0-4.0) and the AUC was 0.68 (95% CI: 0.64-0.72). Meta-regression analysis revealed that cut-off values accounted for the heterogeneity of sensitivity and sample size (> = 150) accounted for the heterogeneity of specificity.

CONCLUSIONS

Based on the results of our meta-analysis, LBP had weak sensitivity and specificity in the detection of sepsis. LBP may not be practically recommended for clinical utilization as a single biomarker.

A PCT algorithm for discontinuation of antibiotic therapy is a cost-effective way to reduce antibiotic exposure in adult intensive care patients with sepsis

OBJECTIVE

Procalcitonin (PCT) is a specific marker for differentiating bacterial from non-infective causes of inflammation. It can be used to guide initiation and duration of antibiotic therapy in intensive care unit (ICU) patients with suspected sepsis, and might reduce the duration of hospital stay. Limiting antibiotic treatment duration is highly important because antibiotic over-use may cause patient harm, prolonged hospital stay, and resistance development. Several systematic reviews show that a PCT algorithm for antibiotic discontinuation is safe, but upfront investment required for PCT remains an important barrier against implementation. The current study investigates to what extent this PCT algorithm is a cost-effective use of scarce healthcare resources in ICU patients with sepsis compared to current practice.

METHODS

A decision tree was developed to estimate the health economic consequences of the PCT algorithm for antibiotic discontinuation from a Dutch hospital perspective. Input data were obtained from a systematic literature review. When necessary, additional information was gathered from open interviews with clinical chemists and intensivists. The primary effectiveness measure is defined as the number of antibiotic days, and cost-effectiveness is expressed as incremental costs per antibiotic day avoided.

RESULTS

The PCT algorithm for antibiotic discontinuation is expected to reduce hospital spending by circa € 3503 per patient, indicating savings of 9.2%. Savings are mainly due to reductions in length of hospital stay, number of blood cultures performed, and, importantly, days on antibiotic therapy. Probabilistic and one-way sensitivity analyses showed the model outcome to be robust against changes in model inputs.

CONCLUSION

Proven safe, a PCT algorithm for antibiotic discontinuation is a cost-effective means of reducing antibiotic exposure in adult ICU patients with sepsis, compared to current practice. Additional resources required for PCT are more than offset by downstream cost savings. This finding is highly important given the aim of preventing widespread antibiotic resistance.

Is there value in plasma cytokine measurements in patients with severe trauma and sepsis?

For the past thirty years, since IL-1β and TNFα were first cloned, there have been efforts to measure plasma cytokine concentrations in patients with severe sepsis and trauma, and to use these measurements to predict clinical outcome and response to therapies. The numbers of cytokines and chemokines that have been measured in the plasma have literally exploded with the development of multiplex immune approaches. Dozens of relatively small cohort studies have shown plasma cytokine concentrations correlating with outcome in sepsis and trauma. Despite what appears to be a consensus that plasma cytokine concentrations should be useful in the clinical setting, only two cytokines, IL-6 and procalcitonin, have approached routine clinical use. IL-6 has been used as a research tool for entry into sepsis-intervention trials, while procalcitonin is being used clinically at a large number of institutions to distinguish sepsis from other inflammatory processes. For most cytokines, the relative lack of sensitivity and specificity of individual or multiplex cytokine measurements has hindered their utility to predict clinical trajectory in individual patients. The problem rests with a general misunderstanding of cytokine biology, failing to appreciate the general paracrine nature of these mediators, the presence of binding proteins, chaperones and inhibitors in the plasma, and the rapid clearance of these proteins by binding to cell receptors and clearance predominantly by the kidney. The future of using plasma cytokine measurements as an indicator of sepsis/trauma severity or predicting outcome is generally behind us, although there is optimism that procalcitonin measurements may ultimately prove to have utility in the diagnosis of severe sepsis.

Accuracy of plasma sTREM-1 for sepsis diagnosis in systemic inflammatory patients: a systematic review and meta-analysis

Introduction

Early diagnosis of sepsis is vital to the clinical course and outcome of septic patients. Recently, soluble triggering receptor expressed on myeloid cells-1 (sTREM-1) appears to be a potential marker of infection. The objective of this systematic review and meta-analysis was to evaluate the accuracy of plasma sTREM-1 for sepsis diagnosis in systemic inflammatory patients.

Methods

A systematic literature search of PubMed, Embase and Cochrane Central Register of Controlled Trials was performed using specific search terms (up to 15 October 2012). Studies were included if they assessed the accuracy of plasma sTREM-1 for sepsis diagnosis in adult patients with systemic inflammatory response syndrome (SIRS) and provided sufficient information to construct a 2 X 2 contingency table.

Results

Eleven studies with a total of 1,795 patients were included. The pooled sensitivity and specificity was 79% (95% confidence interval (CI), 65 to 89) and 80% (95% CI, 69 to 88), respectively. The positive likelihood ratio, negative likelihood ratio and diagnostic odds ratio were 4.0 (95% CI, 2.4 to 6.9), 0.26 (95% CI, 0.14 to 0.48), and 16 (95% CI, 5 to 46), respectively. The area under the curve of the summary receiver operator characteristic was 0.87 (95% CI, 0.84 to 0.89). Meta-regression analysis suggested that patient sample size and assay method were the main sources of heterogeneity. Publication bias was suggested by an asymmetrical funnel plot (P = 0.02).

Conclusions

The present meta-analysis showed that plasma sTREM-1 had a moderate diagnostic performance in differentiating sepsis from SIRS. Accordingly, plasma sTREM-1 as a single marker was not sufficient for sepsis diagnosis in systemic inflammatory patients.

Role of procalcitonin in managing adult patients with respiratory tract infections

Respiratory infections remain the most common reason why patients seek medical care in ambulatory and hospital settings, and they are the most frequent precursor of sepsis. In light of the limitations of clinical signs and symptoms and traditional microbiologic diagnostics for respiratory infections, blood biomarkers that correlate with the presence and extent of bacterial infections may provide additional useful information to improve diagnostic and prognostic efforts and help with therapeutic decisions in individual patients. A growing body of evidence supports the use of procalcitonin (PCT) to differentiate bacterial from viral respiratory diagnoses, to help risk stratify patients, and to guide antibiotic therapy decisions about initial need for, and optimal duration of, therapy. Although still relatively new on the clinical frontier, a series of randomized controlled trials have evaluated PCT protocols for antibiotic-related decision making and have included patients from different clinical settings and with different severities of respiratory infection. In these trials, initial PCT levels were effective in guiding decisions about the initiation of antibiotic therapy in lower-acuity patients, and subsequent measurements were effective for guiding duration of therapy in higher-acuity patients, without apparent harmful effects. Recent European respiratory infection guidelines now also recognize this concept. As with any other laboratory test, PCT should not be used on a stand-alone basis. Rather, it must be integrated into clinical protocols, together with clinical, microbiologic data and with results from clinical risk scores. The aim of this review is to summarize recent evidence about the usefulness of PCT in patients with lower respiratory tract infections and to discuss the potential benefits and limitations of this marker when used for clinical decision making.

Serum decoy receptor 3, a potential new biomarker for sepsis

BACKGROUND

Sepsis, a common deadly systemic infection caused by a variety of pathogens, has some clinical symptoms similar to the systemic inflammatory response syndrome (SIRS), a whole-body non-infectious inflammatory reaction to severe insults, such as burn, trauma, hypotensive shock and so on. Treatment of sepsis depends mainly on anti-microbial, while remedy for SIRS might require steroids that could possibly enhance the spread of microbes. Unfortunately, it is very difficult to distinguish these two completely different serious conditions without blood culture, which takes days to grow and identify causative pathogens. We examined a biomarker, serum decoy receptor 3 (DcR3), was evaluated for its utility in the differential diagnosis between sepsis and SIRS.

METHODS

Serum DcR3 level in 118 healthy controls, 24 sepsis patients and 43 SIRS patients, was quantitatively measured by enzyme-linked immunosorbent assay (ELISA).

RESULTS

The serum DcR3 was significantly increased in sepsis patients compared with SIRS patients and healthy controls (6.11±2.58 ng/ml vs 2.62±1.46 ng/ml, and 0.91±0.56 ng/ml, respectively, p<0.001). The areas under the receiver operating characteristic curve of DcR3 for the normal vs. SIRS, normal vs. sepsis and SIRS vs. sepsis were 0.910 (0.870-0.950), 0.992 (0.984-1.000) and 0.896 (0.820-0.973), respectively. In addition, the DcR3 exhibited a positive correlation coefficient with APACHE II score, a most commonly used index for the severity of sepsis (r=0.556, p=0.005).

CONCLUSION

The serum DcR3 has a potential to serve as a new biomarker for sepsis with its high specificity and sensitivity.

Reduction in antibiotic use through procalcitonin testing in patients in the medical admission unit or intensive care unit with suspicion of infection

We report an evaluation of the utility of serum procalcitonin (PCT) measurement as an additional diagnostic tool to support initiating or withholding antibiotics in clinical situations where there is a clinical suspicion of infection but the diagnosis is uncertain. During a six-month period, 99 patients on the medical admission unit (MAU) with suspected infection, and 42 patients on the intensive care unit (ICU) with clinical signs or physiological parameters suggesting possible new infection, had serum PCT concentration measured with the result available within 90min of the request. The test was initiated by the microbiology/infection team during clinical consultations to support the antibiotic decision. On the basis of low PCT values, antibiotics were withheld in MAU on 52 occasions and in ICU on 42 occasions. Patients were followed up prospectively for a week. There was neither progression of bacterial infection requiring antibiotics, nor complications or infection-related mortality in any patients who were denied antibiotics on either MAU or ICU. Without the PCT value it is likely that all of these patients would have received empirical antibiotics. Reduction in unnecessary antibiotic usage was made without any adverse effects on these patients and there was a clear reduction in antibiotic prescribing with cost reduction implications. PCT has the potential to become a valuable tool in antibiotic management.

Soluble triggering receptor expressed on myeloid cells-1 is an early marker of infection in the surgical intensive care unit

BACKGROUND

To determine the value of soluble triggering receptor expressed on myeloid cells-1 (sTREM-1) in early differentiation of systemic inflammatory response syndrome (SIRS) from infection in patients in a surgical intensive care unit (ICU).

METHODS

Patients were enrolled if there was clinical suspicion of infection and they fulfilled at least two criteria of SIRS at the time of admission to the ICU. The patients were classified as having SIRS (no infection; n = 37) or infection (n = 56) on the basis of the decision of the treating physician and bacteriological evidence of infection. The plasma concentrations of sTREM-1 in the two groups were compared.

RESULTS

Patients with infection had significantly higher sTREM-1 concentrations than patients with SIRS: Median 398 pg/mL (interquartile range [IQR] 302, 552) vs. 78 pg/mL (IQR 28, 150), respectively (p < 0.0001). At a cut-off of 230 pg/mL, sTREM-1 correctly identified patients suffering from infection with 96% sensitivity and 91% specificity.

CONCLUSIONS

In the present study, sTREM-1 was an accurate tool for differentiating SIRS from infection in patients in the surgical ICU.

A rapid enzyme-linked immunosorbent assay with two modes of detection for measuring cytokine concentration

Interleukin (IL)-6 and IL-8 were measured in 101 serum samples collected from eight intensive-care unit patients using a polystyrene-based stick enzyme-linked immunosorbent assay (STICKELISA) system. This system consisted of an immobilized-antibody ELISA stick and a noncontact spectrophotometer. Cytokine concentration was detected by two ways: first, rapidly and semi-quantitatively by naked-eye observation of the color change and second, quantitatively using the spectrophotometer for accurate concentration determination. The spectrophotometric assay enabled the quantitation of as little as 100 pg/mL cytokine and took only 45 min to complete. There was a good agreement between the STICKELISA observations and data obtained using a plate ELISA system. The agreement between STICKELISA naked-eye observation and plate ELISA determination was 94 and 85% for IL-6 and IL-8, respectively. The correlation coefficients between the STICKELISA spectrophotometric determination and plate ELISA determination were 0.88 and 0.91 for IL-6 and IL-8, respectively, in a 0.1-5 ng/mL cytokine concentration range. These results demonstrate that the STICKELISA system is a simple, rapid, and quantitative method for bedside cytokine measurement in critical-care settings.

Diagnostic Efficacy and Prognostic Value of Serum Procalcitonin Concentration in Patients With Suspected Sepsis

Background: Procalcitonin is released in response to bacterial infection and it is not released in Inflammatory and viral diseases.

Objective: To show the diagnostic efficacy and prognostic value of procalcitonin for sepsis.

Methods: A consecutive series of 103 patients with suspected sepsis were admitted to the intensive care unit over a 2-year period. During the first 24 hours of the admission procalcitonin, C-reactive protein, and complement proteins were determined. The diagnostic efficacy was tested with predictive values, likelihood ratios, receiver operating characteristic curves, and multiple logistic regression. The association of procalcitonin with mortality was assessed by the Multivariate Cox proportional hazards model.

Results: Procalcitonin had a better positive likelihood ratio than C-reactive protein —2.2 (95% confidence interval: 1.3-3.7) versus 1.1 (95% confidence interval: 0.9-1.2). Sequential Organ Failure Assessment yielded the highest discriminative value, with an area under the curve of 0.82 (95% confidence interval: 0.73-0.92), followed by procalcitonin (0.81; 95% confidence interval: 0.72-0.89). Multivariate regression analysis showed procalcitonin (adjusted odds ratio: 3.8; 95% confidence interval: 1.2-11.8) and Sequential Organ Failure Assessment score (adjusted odds ratio: 5.3; 95% confidence interval: 1.4-19.9) as the only variables independently associated with infection. Multivariate Cox regression analysis revealed that procalcitonin was not independently associated with mortality.

Conclusions: The diagnostic accuracy of procalcitonin was higher than C-reactive protein and complement proteins. Procalcitonin in combination with Sequential Organ Failure Assessment was useful to diagnose infection. C-reactive protein, Sequential Organ Failure Assessment score, age, and gender showed to be helpful to improve the prediction of mortality risk, but not procalcitonin.

Evaluation of serum C-reactive protein, procalcitonin, tumor necrosis factor alpha, and interleukin-10 levels as diagnostic and prognostic parameters in patients with community-acquired sepsis, severe sepsis, and septic shock

The diagnostic value of procalcitonin, C-reactive protein, tumor necrosis factor-alpha, and interleukin-10 levels in differentiating sepsis from severe sepsis and the prognostic value of these levels in predicting outcome were evaluated and compared in patients with community-acquired sepsis, severe sepsis, and septic shock in the first 72 h of admission to the hospital. Thirty-nine patients were included in the study. The severe sepsis and septic shock cases were combined in a single "severe sepsis" group, and all comparisons were made between the sepsis (n=21 patients) and the severe sepsis (n=18 patients) groups. Procalcitonin levels in the severe sepsis group were found to be significantly higher at all times of measurements within the first 72 h and were significantly higher at the 72nd hour in patients who died. Procalcitonin levels that remain elevated at the 72nd hour indicated a poor prognosis. C-reactive protein levels were not significantly different between the groups, nor were they indicative of prognosis. No significant differences in the levels of tumor necrosis factor-alpha were found between the sepsis and severe sepsis groups; however, levels were higher at the early stages (at admission and the 24th hour) in patients who died. Interleukin-10 levels were also higher in the severe sepsis group and significantly higher at all times of measurement in patients who died. When the diagnostic and prognostic values at admission were evaluated, procalcitonin and interleukin-10 levels were useful in discriminating between sepsis and severe sepsis, whereas tumor necrosis factor-alpha and interleukin-10 levels were useful in predicting which cases were likely to have a fatal outcome.

Neutrophil CD64 is an improved indicator of infection or sepsis in emergency department patients

CONTEXT

Sepsis, affecting millions of individuals annually with an associated high mortality rate, is among the top 10 causes of death. In addition, improvements in diagnostic tests for detecting and monitoring sepsis and infection have been limited in the last 25 years. Neutrophil CD64 expression has been proposed as an improved diagnostic test for the evaluation of infection and sepsis.

OBJECTIVE

To evaluate the diagnostic performance of a quantitative flow cytometric assay for leukocyte CD64 expression in comparison with the standard tests for infection/sepsis in an ambulatory care setting.

DESIGN

Prospective analysis of 100 blood samples from patients from an emergency department setting in a 965-bed tertiary care suburban community hospital was performed for neutrophil CD64 expression, C-reactive protein, erythrocyte sedimentation rate, and complete blood count. The laboratory findings were compared with a clinical score for the likelihood of infection/sepsis, which was obtained by a blinded retrospective chart review.

RESULTS

The diagnostic performance, as gauged by the clinical score, varied with neutrophil CD64 (sensitivity 87.9%, specificity 71.2%, efficiency 76.8%) and outperformed C-reactive protein (sensitivity 88.2%, specificity 59.4%, efficiency 69.4%), absolute neutrophil count (sensitivity 60.0%, specificity 50.8%, efficiency 53.8%), myeloid left shift (sensitivity 68.2%, specificity 76.3%, efficiency 73.3%), and sedimentation rate (sensitivity 50.0%, specificity 65.5%, efficiency 61.0%).

CONCLUSION

Neutrophil CD64 expression quantitation provides improved diagnostic detection of infection/sepsis compared with the standard diagnostic tests used in current medical practice.

Procalcitonin does discriminate between sepsis and systemic inflammatory response syndrome

AIMS

To evaluate whether procalcitonin (PCT) and C reactive protein (CRP) are able to discriminate between sepsis and systemic inflammatory response syndrome (SIRS) in critically ill children.

METHODS

Prospective, observational study in a paediatric intensive care unit. Kinetics of PCT and CRP were studied in patients undergoing open heart surgery with cardiopulmonary bypass (CPB) (SIRS model; group I1) and patients with confirmed bacterial sepsis (group II).

RESULTS

In group I, PCT median concentration was 0.24 ng/ml (reference value <2.0 ng/ml). There was an increment of PCT concentrations which peaked immediately after CPB (median 0.58 ng/ml), then decreased to 0.47 ng/ml at 24 h; 0.33 ng/ml at 48 h, and 0.22 ng/ml at 72 h. CRP median concentrations remained high on POD1 (36.6 mg/l) and POD2 (13.0 mg/l). In group II, PCT concentrations were high at admission (median 9.15 ng/ml) and subsequently decreased in 11/14 patients who progressed favourably (median 0.31 ng/ml). CRP levels were high in only 11/14 patients at admission. CRP remained high in 13/14 patients at 24 h; in 12/14 at 48 h; and in 10/14 patients at 72 h. Median values were 95.0, 50.9, 86.0, and 20.3 mg/l, respectively. The area under the ROC curve was 0.99 for PCT and 0.54 for CRP. Cut off concentrations to differentiate SIRS from sepsis were >2 ng/ml for PCT and >79 mg/l for CRP.

CONCLUSION

PCT is able to differentiate between SIRS and sepsis while CRP is not. Moreover, unlike CRP, PCT concentrations varied with the evolution of sepsis.

Comparison of neutrophil CD64 expression, manual myeloid immaturity counts, and automated hematology analyzer flags as indicators of infection or sepsis

There is a clear need for improved indicators of infection or sepsis to increase the sensitivity and specificity of both diagnosis and therapeutic monitoring. One of the effects of inflammatory cytokines on the innate immune response is the rapid up-regulation of CD64 expression on the neutrophil membrane. We and others have hypothesized that the measurement of neutrophil CD64 expression might represent an improved diagnostic indicator of infection and sepsis. In this study we assessed the relative ability of flow cytometric neutrophil CD64 measurements, neutrophil counts, myeloid immaturity differential counts, and flagging on an automated hematology analyzer to correlate with the presence of infection, as determined by a retrospective clinical scoring system of infection or sepsis. A total of 160 blood samples were randomly selected to derive equal proportions of the 3 categories of flags on a Coulter STKS blood counter that indicate the presence of a myeloid left shift. The patients for these samples were scored by retrospective chart review and placed into 4 groups on the basis of likelihood of infection, sepsis, or severe tissue injury. Neutrophil CD64 expression demonstrated a superior sensitivity (94.1%), specificity (84.9%), and positive predictive likelihood ratio (6.24), compared with neutrophil counts (sensitivity, 79.4%; specificity, 46.8%; positive predictive likelihood ratio, 1.49), band counts (sensitivity, 87.5%; specificity, 43.5%; positive predictive likelihood ratio, 1.55), myeloid immaturity fraction (sensitivity, 94.6%; specificity, 84.5%; positive predictive likelihood ratio, 2.12), and flagging on an automated hematology analyzer (sensitivity, 94.1%; specificity, 40.5%; positive predictive likelihood ratio, 1.58). Relative to the other laboratory parameters, the neutrophil CD64 parameter also provided the best separation of the 4 clinical groups. The findings indicate that neutrophil CD64 expression as determined by quantitative flow cytometry is an improved diagnostic indicator of infection/sepsis relative to current laboratory indicators of relative or absolute myeloid cell counts or hematology analyzer flagging algorithms.

Improved diagnostic approaches to infection/sepsis detection

Sepsis is a major healthcare problem from the perspective of mortality and economics. Advances in diagnostic detection of infection and sepsis have been slow, but recent advances in both soluble biomarker detection and quantitative cellular measurements promise the availability of improved diagnostic techniques. Though the promise of cytokine measurements reaching clinical practice have not matured, procalcitonin levels are currently available in many countries and appear to offer enhanced diagnostic distinction between bacterial and viral etiologies. Cellular diagnostics is poised to enter clinical laboratory practice in the form of neutrophil CD64 measurements, which offer superior sensitivity and specificity to conventional laboratory assessment of sepsis. Neutrophil CD64 expression is negligible in the healthy state. However, it increases as part of the systemic response to severe infection or sepsis. The combination of cellular proteomics, as in the case of neutrophil CD64 quantification, and selected soluble biomarkers of the inflammatory response, such as procalcitonin or triggering receptor expressed on myeloid cells (TREM)-1, is predicted to remove the current subjectivity and uncertainty in the diagnosis and therapeutic monitoring of infection and sepsis.

Serial monitoring of interleukin-1?, soluble interleukin-2 receptor and lipopolysaccharide binding protein levels after death

We prospectively monitored the postmortem course of interleukin-1beta (IL-1beta), soluble interleukin-2 receptor (sIL-2R) and lipopolysaccharide binding protein (LBP) in septic and non-septic fatalities to evaluate their potential as biochemical postmortem markers of sepsis. Serum concentrations were determined by chemiluminescent immunometric assays. In both the sepsis group and the control group a postmortem increase of IL-1beta levels with the progression of time after death was observed, in both groups mainly starting from the reference concentration of healthy individuals (5 pg/ml) and with no significant differences at later time points postmortem. SIL-2R (reference limit 1,000 U/ml) was highly elevated in all individuals included in the sepsis group at all time points postmortem with statistically significant differences between the sepsis and control groups (p<0.01). An excessive postmortem decrease of sIL-2R serum levels associated with progression of time after death was observed in all cases included in the sepsis group in contrast to just 1 out of 16 control cases. LBP (reference limit <10 g/ml) was elevated in all sepsis cases whereas in the control group LBP levels were below 10 microg/ml in 88%. The postmortem time course of LBP serum concentrations showed a continuous increase in both the sepsis and control groups. We conclude that sIL-2R and LBP seem to represent appropriate diagnostic tools for the postmortem diagnosis of sepsis in forensic autopsy practice. sIL-2R serum levels above 1,000 U/ml and LBP serum levels above 10 microg/ml in peripheral venous blood obtained in the early postmortem interval can be regarded as diagnostic hints for an underlying septic condition in a deceased person.

Guide to a systematic physical assessment in the infant with suspected infection and/or sepsis

This article provides the resources for the bedside caregiver to conduct a focused physical assessment of the infant with suspected sepsis. The importance of obtaining a complete history to identify associated obstetric and neonatal risk factors is emphasized. Further evaluation of the infant's clinical presentation for signs and symptoms suggestive of a systemic inflammatory response to infection is discussed, along with a step-by-step guide to a systematic physical assessment. Strategies to evaluate physical findings in context with the available diagnostic data to develop a differential diagnosis are provided. The international consensus definitions for the sepsis continuum are presented and are compared and contrasted to the definitions more commonly used in the neonatal population. The article provides tables that can serve as checklists to structure a thorough obstetric and neonatal history and to further evaluate the infant's systemic inflammatory response to infection.

Quantifying Uncertainty: Physicians' Estimates of Infection in Critically Ill Neonates and Children

To determine the diagnostic accuracy of physicians' prior probability estimates of serious infection in critically ill neonates and children, we conducted a prospective cohort study in 2 intensive care units. Using available clinical, laboratory, and radiographic information, 27 physicians provided 2567 probability estimates for 347 patients (follow-up rate, 92%). The median probability estimate of infection increased from 0% (i.e., no antibiotic treatment or diagnostic work-up for sepsis), to 2% on the day preceding initiation of antibiotic therapy, to 20% at initiation of antibiotic treatment (P<.001). At initiation of treatment, predictions discriminated well between episodes subsequently classified as proven infection and episodes ultimately judged unlikely to be infection (area under the curve, 0.88). Physicians also showed a good ability to predict blood culture-positive sepsis (area under the curve, 0.77). Treatment and testing thresholds were derived from the provided predictions and treatment rates. Physicians' prognoses regarding the presence of serious infection were remarkably precise. Studies investigating the value of new tests for diagnosis of sepsis should establish that they add incremental value to physicians' judgment.

Plasma endotoxin concentration in horses: a methods study

BACKGROUND

Accurate determination of plasma endotoxin concentration is critical for ex vivo and in vitro cellular and molecular studies of endotoxemia in horses. However, reports are conflicting with respect to anticoagulant, handling, and sample preparation.

OBJECTIVE

The purpose of this study was to determine the effect of blood sample fraction and handling time on measurement of endotoxin concentration in horses.

METHODS

Whole blood, anticoagulated with 3.8% (0.12 M) sodium citrate (9:1), was collected from 5 healthy horses. Whole blood (WB), platelet-rich plasma (PRP), and platelet-poor plasma (PPP) were spiked with endotoxin (2 EU/mL). Endotoxin-spiked WB samples were centrifuged immediately to generate PRP for measurement. Endotoxin concentration was subsequently measured by Limulus amebocyte assay at 0, 15, 30, 45, and 60 minutes. Assays were performed in triplicate and results were analyzed using Student's t-test, with significance set at P <.05.

RESULTS

Mean endotoxin concentrations in 2 EU/mL-spiked WB were significantly different from those in PPP at all time points tested. Recovery of endotoxin in PRP generated from WB was significantly diminished after just 15 minutes.

CONCLUSION

PRP generated from WB is significantly more reliable than PPP in determining endotoxin concentration ex vivo. Measurement of endotoxin in PRP generated from WB was significantly diminished after 15 min, identifying a time frame within which to process blood samples for endotoxin analysis.

Procalcitonin as a marker of bacterial infection in the emergency department: an observational study

Introduction

Procalcitonin (PCT) has been proposed as a marker of infection in critically ill patients; its level is related to the severity of infection. We evaluated the value of PCT as a marker of bacterial infection for emergency department patients.

Methods

This prospective observational study consecutively enrolled 120 adult atraumatic patients admitted through the emergency department of a 3000-bed tertiary university hospital in May 2001. Fifty-eight patients were infected and 49 patients were not infected. The white blood cell counts, the serum C-reactive protein (CRP) level (mg/l), and the PCT level (ng/ml) were compared between the infected and noninfected groups of patients.

Results

A white blood cell count >12,000/mm³ or <4000/mm³ was present in 36.2% of the infected patients and in 18.4% of the noninfected patients. The best cut-off serum levels for PCT and CRP, identified using the Youden's Index, were 0.6 ng/ml and 60 mg/l, respectively. Compared with CRP, PCT had a comparable sensitivity (69.5% versus 67.2%), a lower specificity (64.6% versus 93.9%), and a lower area under the receiver operating characteristic curve (0.689 versus 0.879). PCT levels, but not CRP levels, were significantly higher in bacteremic and septic shock patients. Multivariate logistic regression identified that a PCT level ≥ 2.6 ng/ml was independently associated with the development of septic shock (odds ratio, 38.3; 95% confidence interval, 5.6–263.5; P < 0.001).

Conclusions

PCT is not a better marker of bacterial infection than CRP for adult emergency department patients, but it is a useful marker of the severity of infection.

The systemic inflammatory response syndrome (SIRS) to identify infected patients in the emergency room

OBJECTIVE

Evaluation of the usefulness of criteria for systemic inflammatory response syndrome (SIRS) compared with the final diagnosis of infection in patients admitted to the emergency room of two university-based hospitals.

DESIGN

Longitudinal cohort study.

SETTING

Hospital Universitario San Vicente de Paul and Hospital General de Medellín, Medellín, Colombia. PATIENTS. Seven hundred thirty-four patients with suspected infection as main diagnosis for admittance into the emergency room.

MEASUREMENTS AND RESULTS

Sensitivity, specificity, predictive values and likelihood ratios (LR) of SIRS criteria at admission were determined using, as gold standards, the diagnosis at the time of discharge based on clinical history and evolution, and microbiological confirmation of infection. SIRS criteria were met by 503 patients (68.5%); the discharge diagnosis of infection was found in 657 (89.4%) and 276 (37%) had microbiological confirmation. SIRS criteria exhibited a sensitivity of 69%, specificity of 35%, positive predictive value (PPV) of 90%, negative predictive value (NPV) of 12% and positive LR of 1.06. There were no differences between the two gold standards.

CONCLUSIONS

The finding of two or more SIRS criteria was of little usefulness for diagnosis of infection. It is necessary to work with new criteria and probably with biological markers, in order to obtain a simple, precise and operative definition of the sepsis phenomenon.

Diagnostic value of procalcitonin, interleukin-6, and interleukin-8 in critically ill patients admitted with suspected sepsis

To assess the diagnostic value of procalcitonin (PCT), interleukin (IL)-6, IL-8, and standard measurements in identifying critically ill patients with sepsis, we performed prospective measurements in 78 consecutive patients admitted with acute systemic inflammatory response syndrome (SIRS) and suspected infection. We estimated the relevance of the different parameters by using multivariable regression modeling, likelihood-ratio tests, and area under the receiver operating characteristic curves (AUC). The final diagnosis was SIRS in 18 patients, sepsis in 14, severe sepsis in 21, and septic shock in 25. PCT yielded the highest discriminative value, with an AUC of 0.92 (CI, 0.85 to 1.0), followed by IL-6 (0.75; CI, 0.63 to 0.87), and IL-8 (0.71; CI, 0.59 to 0.83; p < 0.001). At a cutoff of 1.1 ng/ml, PCT yielded a sensitivity of 97% and a specificity of 78% to differentiate patients with SIRS from those with sepsis-related conditions. Median PCT concentrations on admission (ng/ ml, range) were 0.6 (0 to 5.3) for SIRS; 3.5 (0.4 to 6.7) for sepsis; 6.2 (2.2 to 85) for severe sepsis; and 21.3 (1.2 to 654) for septic shock (p < 0.001). The addition of PCT to a model based solely on standard indicators improved the predictive power of detecting sepsis (likelihood ratio test; p = 0.001) and increased the AUC value for the routine value-based model from 0.77 (CI, 0.64 to 0.89) to 0.94 (CI, 0.89 to 0.99; p = 0.002). In contrast, no additive effect was seen for IL-6 (p = 0.56) or IL-8 (p = 0.14). Elevated PCT concentrations appear to be a promising indicator of sepsis in newly admitted, critically ill patients capable of complementing clinical signs and routine laboratory parameters suggestive of severe infection.

Pediatric sepsis and multiple organ dysfunction syndrome

Systemic inflammatory response syndrome may be viewed as the systemic expression of cytokine signals that normally function on an autocrine or paracrine level. Sepsis is defined as systemic inflammatory response syndrome caused by an infection. Multiple organ dysfunction syndrome may represent the end stage of severe systemic inflammatory response syndrome or sepsis. Many cells are involved, including endothelial cells and leukocytes and multiple proinflammatory and antiinflammatory mediators (cytokines, oxygen free radicals, coagulation factors, and so forth). Various pathophysiologic mechanisms have been postulated. The most popular theory is that the inflammatory process loses its autoregulatory capacity; however, microcirculatory dysregulation and apoptosis may also be important, and a new paradigm posits a complex nonlinear system. Many new treatments have been studied recently. The usefulness of immune modulating diets remains to be evaluated. Molecular immunomodulation is still of unclear value. The therapy of sepsis and multiple organ dysfunction syndrome remains mainly supportive.

Impact of Antibiotic Resistance on the Treatment of Gram-negative Sepsis

Resistance among gram-negative organisms has greatly complicated the care of the septic patient. An understanding of the likely source of infection, the epidemiologic risk of the patient being exposed to an antibiotic-resistant organism, and the specific vulnerabilities of the host are essential to the proper selection of empiric antimicrobial therapy. In this report, we discuss the epidemiology, antibiotic resistance mechanisms, microbiology, treatment strategies, and diagnostic and therapeutic innovations in the approach to the septic patient.