Severe respiratory viral infection induces procalcitonin in the absence of bacterial pneumonia

The long Pentraxin PTX3 serves as an early predictive biomarker of co-infections in COVID-19

BACKGROUND

COVID-19 clinical course is highly variable and secondary infections contribute to COVID-19 complexity. Early detection of secondary infections is clinically relevant for patient outcome. Procalcitonin (PCT) and C-reactive protein (CRP) are the most used biomarkers of infections. Pentraxin 3 (PTX3) is an acute phase protein with promising performance as early biomarker in infections. In patients with COVID-19, PTX3 plasma concentrations at hospital admission are independent predictor of poor outcome. In this study, we assessed whether PTX3 contributes to early identification of co-infections during the course of COVID-19.

METHODS

We analyzed PTX3 levels in patients affected by COVID-19 with (n = 101) or without (n = 179) community or hospital-acquired fungal or bacterial secondary infections (CAIs or HAIs).

FINDINGS

PTX3 plasma concentrations at diagnosis of CAI or HAI were significantly higher than those in patients without secondary infections. Compared to PCT and CRP, the increase of PTX3 plasma levels was associated with the highest hazard ratio for CAIs and HAIs (aHR 11.68 and 24.90). In multivariable Cox regression analysis, PTX3 was also the most significant predictor of 28-days mortality or intensive care unit admission of patients with potential co-infections, faring more pronounced than CRP and PCT.

INTERPRETATION

PTX3 is a promising predictive biomarker for early identification and risk stratification of patients with COVID-19 and co-infections.

FUNDING

Dolce & Gabbana fashion house donation; Ministero della Salute for COVID-19; EU funding within the MUR PNRR Extended Partnership initiative on Emerging Infectious Diseases (Project no. PE00000007, INF-ACT) and MUR PNRR Italian network of excellence for advanced diagnosis (Project no. PNC-E3-2022-23683266 PNC-HLS-DA); EU MSCA (project CORVOS 860044).

A dual role for CRTH2 in acute lung injury

Acute respiratory distress syndrome (ARDS) is a life-threatening clinical condition defined by rapid-onset respiratory failure following acute lung injury (ALI). The high mortality rate and rising incidence of ARDS due to COVID-19 make it an important research priority. Here we sought to investigate the role of chemoattractant receptor-homologous molecule expressed on Th2 cells (CRTH2) in ARDS. CRTH2 is a G protein-coupled receptor best studied in the context of type 2 immunity, but it also exerts effects on neutrophilic inflammation. To evaluate its role in mouse models of ARDS, we first examined its expression pattern on murine neutrophils. We found it is expressed on neutrophils, but only after extravasation into the lung. Next, we showed that CRTH2 expression on extravasated lung neutrophils promotes cell survival, as genetic deletion of CRTH2 and pharmacologic inhibition of CRTH2 using fevipiprant both led to increased apoptosis in vitro. We then evaluated the role of CRTH2 in vivo using a murine model of LPS-induced ALI. In line with the pro-inflammatory effects of CRTH2 in vitro, we observed improvement of lung injury in CRTH2-deficient mice in terms of vascular leak, weight loss and survival after LPS administration. However, neutrophilic inflammation was elevated, not suppressed in the CRTH2 KO. This finding indicated a second mechanism offsetting the pro-survival effect of CRTH2 on neutrophils. Bulk RNAseq of lung tissue indicated impairments in type 2 immune signaling in the CRTH2 KO, and qPCR and ELISA confirmed downregulation of IL-4, which is known to suppress neutrophilic inflammation. Thus, CRTH2 may play a dual role in ALI, directly promoting neutrophil cell survival, but indirectly suppressing neutrophil effector function via IL-4.

Disease-specific plasma protein profiles in patients with fever after traveling to tropical areas

Fever is common among individuals seeking healthcare after traveling to tropical regions. Despite the association with potentially severe disease, the etiology is often not determined. Plasma protein patterns can be informative to understand the host response to infection and can potentially indicate the pathogen causing the disease. In this study, we measured 49 proteins in the plasma of 124 patients with fever after travel to tropical or subtropical regions. The patients had confirmed diagnoses of either malaria, dengue fever, influenza, bacterial respiratory tract infection, or bacterial gastroenteritis, representing the most common etiologies. We used multivariate and machine learning methods to identify combinations of proteins that contributed to distinguishing infected patients from healthy controls, and each other. Malaria displayed the most unique protein signature, indicating a strong immunoregulatory response with high levels of IL10, sTNFRI and II, and sCD25 but low levels of sCD40L. In contrast, bacterial gastroenteritis had high levels of sCD40L, APRIL, and IFN-γ, while dengue was the only infection with elevated IFN-α2. These results suggest that characterization of the inflammatory profile of individuals with fever can help to identify disease-specific host responses, which in turn can be used to guide future research on diagnostic strategies and therapeutic interventions.

Plasma Insulin-like Growth Factor-Binding Protein-2 of Critically Ill Patients Is Related to Disease Severity and Survival

Insulin-like growth factor-binding protein (IGFBP)-2 regulates the bioactivity of the anabolic hormone's insulin-like growth factors, which are decreased in sepsis and contribute to the catabolic status of severely ill patients. The circulating levels of IGFBP-2 in critical illness have been rarely studied; therefore, we evaluated IGFBP-2 plasma levels in patients with systemic inflammatory response syndrome (SIRS) or sepsis as well as healthy controls. Our analysis of 157 SIRS/sepsis patients revealed higher plasma IGFBP-2 levels compared to 22 healthy controls. Plasma IGFBP-2 levels correlated positively with procalcitonin but not with C-reactive protein, interleukin-6, or the leukocyte count. Septic shock patients exhibited higher IGFBP-2 levels than those with SIRS. Bacterial or SARS-CoV-2 infection did not influence plasma IGFBP-2 levels. There was no difference in the IGFBP-2 levels between ventilated and non-ventilated SIRS/sepsis patients, and vasopressor therapy did not alter these levels. Dialysis patients had elevated plasma IGFBP-2 levels. Survivors had lower plasma IGFBP-2 levels than non-survivors. In conclusion, our study indicates that plasma IGFBP-2 levels are associated with disease severity, renal failure, and mortality in SIRS/sepsis patients.

Society of Critical Care Medicine and the Infectious Diseases Society of America Guidelines for Evaluating New Fever in Adult Patients in the ICU

RATIONALE

Fever is frequently an early indicator of infection and often requires rigorous diagnostic evaluation.

OBJECTIVES

This is an update of the 2008 Infectious Diseases Society of America and Society (IDSA) and Society of Critical Care Medicine (SCCM) guideline for the evaluation of new-onset fever in adult ICU patients without severe immunocompromise, now using the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) methodology.

PANEL DESIGN

The SCCM and IDSA convened a taskforce to update the 2008 version of the guideline for the evaluation of new fever in critically ill adult patients, which included expert clinicians as well as methodologists from the Guidelines in Intensive Care, Development and Evaluation Group. The guidelines committee consisted of 12 experts in critical care, infectious diseases, clinical microbiology, organ transplantation, public health, clinical research, and health policy and administration. All task force members followed all conflict-of-interest procedures as documented in the American College of Critical Care Medicine/SCCM Standard Operating Procedures Manual and the IDSA. There was no industry input or funding to produce this guideline.

METHODS

We conducted a systematic review for each population, intervention, comparison, and outcomes question to identify the best available evidence, statistically summarized the evidence, and then assessed the quality of evidence using the GRADE approach. We used the evidence-to-decision framework to formulate recommendations as strong or weak or as best-practice statements.

RESULTS

The panel issued 12 recommendations and 9 best practice statements. The panel recommended using central temperature monitoring methods, including thermistors for pulmonary artery catheters, bladder catheters, or esophageal balloon thermistors when these devices are in place or accurate temperature measurements are critical for diagnosis and management. For patients without these devices in place, oral or rectal temperatures over other temperature measurement methods that are less reliable such as axillary or tympanic membrane temperatures, noninvasive temporal artery thermometers, or chemical dot thermometers were recommended. Imaging studies including ultrasonography were recommended in addition to microbiological evaluation using rapid diagnostic testing strategies. Biomarkers were recommended to assist in guiding the discontinuation of antimicrobial therapy. All recommendations issued were weak based on the quality of data.

CONCLUSIONS

The guidelines panel was able to formulate several recommendations for the evaluation of new fever in a critically ill adult patient, acknowledging that most recommendations were based on weak evidence. This highlights the need for the rapid advancement of research in all aspects of this issue-including better noninvasive methods to measure core body temperature, the use of diagnostic imaging, advances in microbiology including molecular testing, and the use of biomarkers.

Soluble urokinase plasminogen activator receptor and procalcitonin for risk stratification in patients with a suspected infection in the emergency department: a prospective cohort study

BACKGROUND AND IMPORTANCE

Early identification of patients at risk of clinical deterioration may improve prognosis of infected patients in the emergency department (ED). Combining clinical scoring systems with biomarkers may result in a more accurate prediction of mortality than a clinical scoring system or biomarker alone.

OBJECTIVE

The objective of this study is to investigate the performance of the combination of National Early Warning Score-2 (NEWS2) and quick Sequential Organ Failure Assessment (qSOFA) score with soluble urokinase plasminogen activator receptor (suPAR) and procalcitonin to predict 30-day mortality in patients with a suspected infection in the ED.

DESIGN, SETTINGS AND PARTICIPANTS

This was a single-center prospective observational study, conducted in the Netherlands. Patients with suspected infection in the ED were included in this study and followed-up for 30 days. The primary outcome of this study was all cause 30-day mortality. The association between suPAR and procalcitonin with mortality was assessed in subgroups of patients with low and high qSOFA (<1 and ≥1) and low and high NEWS2 (<7 and ≥7).

MAIN RESULTS

Between March 2019 and December 2020, 958 patients were included. A total of 43 (4.5%) patients died within 30 days after ED visit. A suPAR ≥ 6 ng/ml was associated with an increased mortality risk: 5.5 vs. 0.9% ( P  < 0.01) in patients with qSOFA = 0 and 10.7 vs. 2.1% ( P  = 0.02) in patients with qSOFA ≥ 1. There was also an association between procalcitonin ≥0.25 ng/ml and mortality: 5.5 vs. 1.9% ( P  = 0.02) for qSOFA = 0 and 11.9 vs. 4.1% ( P  = 0.03) for qSOFA ≥ 1. Similar associations were found within patients with a NEWS < 7 (5.9 vs. 1.2% for suPAR and 7.0 vs. 1.7% for procalcitonin, P  < 0.001).

CONCLUSION

In this prospective cohort study, suPAR and procalcitonin were associated with increased mortality in patients with either a low or high qSOFA and patients with low NEWS2.

Reduced Reliability of Procalcitonin (PCT) as a Biomarker of Bacterial Superinfection: Concerns about PCT-Driven Antibiotic Stewardship in Critically Ill COVID-19 Patients-Results from a Retrospective Observational Study in Intensive Care Units

BACKGROUND

The aim of this study was to assess whether procalcitonin levels is a diagnostic tool capable of accurately identifying sepsis and ventilator-associated pneumonia (VAP) even in critically ill COVID-19 patients.

METHODS

In this retrospective, observational study, all critically ill COVID-19 patients who survived for ≥2 days in a single university hospital and had at least one serum procalcitonin (PCT) value and associated blood culture and/or culture from a lower respiratory tract specimen available were eligible for the study.

RESULTS

Over the research period, 184 patients were recruited; 67 VAP/BSI occurred, with an incidence rate of 21.82 episodes of VAP/BSI (95% CI: 17.18-27.73) per 1000 patient-days among patients who were included. At the time of a positive microbiological culture, an average PCT level of 1.25-3.2 ng/mL was found. Moreover, also in subjects without positive cultures, PCT was altered in 21.7% of determinations, with an average value of 1.04-5.5 ng/mL. Both PCT and PCT-72 h were not linked to a diagnosis of VAP/BSI in COVID-19 patients, according to the multivariable GEE models (aOR 1.13, 95% CI 0.51-2.52 for PCT; aOR 1.32, 95% CI 0.66-2.64 for PCT-72 h).

CONCLUSION

Elevated PCT levels might not always indicate bacterial superinfections or coinfections in a severe COVID-19 setting.

Procalcitonin as a biomarker to guide treatments for patients with lower respiratory tract infections

INTRODUCTION

Lower respiratory tract infections are amongst the main causes for hospital/intensive care unit admissions and antimicrobial prescriptions. In order to reduce antimicrobial pressure, antibiotic administration could be optimized through procalcitonin-based algorithms.

AREAS COVERED

In this review, we discuss the performances of procalcitonin for the diagnosis and the management of community-acquired and ventilator-associated pneumonia. We provide up-to-date evidence and deliver clear messages regarding the purpose of procalcitonin to reduce unnecessary antimicrobial exposure.

EXPERT OPINION

Antimicrobial pressure and resulting antimicrobial resistances are a major public health issue as well as a daily struggle in the management of patients with severe infectious diseases, especially in intensive care units where antibiotic exposure is high. Procalcitonin-guided antibiotic administration has proven its efficacy in reducing unnecessary antibiotic use in lower respiratory tract infections without excess in mortality, hospital length of stay or disease relapse. Procalcitonin-guided algorithms should be implemented in wards taking care of patients with severe infections. However, procalcitonin performances are different regarding the setting of the infection (community versus hospital-acquired infections) the antibiotic management (start or termination of antibiotic) as well as patient's condition (immunosuppressed or in shock) and we encourage the physicians to be aware of these limitations.

Systemic Inflammation after Aneurysmal Subarachnoid Hemorrhage

Aneurysmal subarachnoid hemorrhage (aSAH) is one of the most severe neurological disorders, with a high mortality rate and severe disabling functional sequelae. Systemic inflammation following hemorrhagic stroke may play an important role in mediating intracranial and extracranial tissue damage. Previous studies showed that various systemic inflammatory biomarkers might be useful in predicting clinical outcomes. Anti-inflammatory treatment might be a promising therapeutic approach for improving the prognosis of patients with aSAH. This review summarizes the complicated interactions between the nervous system and the immune system.

Fatal septic shock due to disseminated coccidioidomycosis: a case series and review of the literature

BACKGROUND

Coccidioidomycosis is a fungal infection endemic to the southwestern United States and regions of Latin America. Disseminated disease occurs in < 1% of cases. Septic shock is even rarer, with high mortality despite therapy. We describe two cases of coccidioidal septic shock. Both patients were older men of Filipino ancestry presenting with respiratory failure and vasopressor-dependent shock. Antifungal drugs were initiated after failure to improve with empiric antibiotics; in both, Coccidioides was isolated from respiratory cultures. Despite aggressive care, both patients ultimately died of their infections. We provide a review of the published literature on this topic.

CONCLUSIONS

Most of the 33 reported cases of coccidioidal septic shock occurred in men (88%) of non-white race and ethnicity (78%). The overall mortality rate was 76%. All survivors received amphotericin B as part of their treatment. Coccidioidomycosis-related septic shock is a rare disease with poor outcomes; delays in diagnosis and treatment are common. Improved diagnostic testing for coccidioidomycosis could enhance recognition of this disease in the future. Although data are limited, early treatment with amphotericin B in cases of coccidioidal septic shock may reduce mortality.

Can we predict critical care mortality with non-conventional inflammatory markers in SARS-CoV-2 infected patients?

BACKGROUND

Severe COVID-19 disease is associated with multiple organ involvement,then failure and often fatal outcomes.In addition,inflammatory mechanisms and cytokine storms,documented in many COVID-19 patients,are responsible for the progression of the disease and high mortality rates.Inflammatory parameters,such as procalcitonin(PCT) and C-reactive protein(CRP), are widely used in clinical practice.

OBJECTIVE

To evaluate the predictive power of non-conventional inflammatory markers regarding mortality risk.

METHODS

In our prospective study 52 patients were followed for 5 days after admission to an intensive care unit immediately with severe SARS-CoV-2 infection.We compared leukocyte-,platelet antisedimentation rate (LAR, PAR),neutrophil lymphocyte ratio(NLR), CRP, PCT levels.

RESULTS

In non-surviving(NSU) patients LAR remained largely constant from D1 to D4 with a statistically significant drop(p <  0.05) only seen on D5.The NSU group showed statistically significant(p <  0.05) elevated LAR medians on D4 and D5, compared to the SU group.NLR values were continually higher in the non-survivor group.The difference between the SU and NSU groups were statistically significant on every examined day.PAR, CRP and PCT levels didn't show any significant differences between the SU and NSU groups.

CONCLUSIONS

In conclusion, this study suggests that LAR and NLR are especially worthy of further investigation as prognostic markers.LAR might be of particular relevance as it is not routinely obtained in current clinical practice.It would seem beneficial to include LAR in data sets to train prognostic artificial intelligence.

Nonutility of procalcitonin for diagnosing bacterial pneumonia in patients with severe COVID-19

Background

Patients hospitalized with COVID-19 are at significant risk for superimposed bacterial pneumonia. However, diagnosing superinfection is challenging due to its clinical resemblance to severe COVID-19. We therefore evaluated whether the immune biomarker, procalcitonin, could facilitate the diagnosis of bacterial superinfection.

Methods

We retrospectively identified 185 patients hospitalized with severe COVID-19 who underwent lower respiratory culture; 85 had evidence of bacterial superinfection. Receiver operating characteristic curve and area under the curve (AUC) analyses were performed to assess the utility of procalcitonin for diagnosing superinfection.

Results

This approach demonstrated that procalcitonin measured at the time of culture was incapable of distinguishing patients with bacterial infection (AUC, 0.52). The AUC not affected by exposure to antibiotics, treatment with immunomodulatory agents, or timing of procalcitonin measurement.

Conclusion

Static measurement of procalcitonin does not aid in the diagnosis of superinfection in severe COVID-19.

Procalcitonin and Adrenomedullin in Infectious Diseases

Calcitonin (CT) and adrenomedullin (ADM) are members of the CT family. Procalcitonin (PCT) is a prohormone of CT. Elevations in serum PCT and ADM levels are associated with severe sepsis and coronavirus disease 2019 (COVID-19). PCT enhances sepsis mortality and it binds to the CGRP receptor, which is a heterodimer of CT receptor-like receptor and receptor activity-modifying protein 1. The N-terminal truncated form of PCT, PCT3-116, is produced by the cleavage of PCT by dipeptidyl peptidase 4 (DPP-4) and is the main form of PCT in serum during sepsis, inducing microvascular permeability. Mid-regional pro-adrenomedullin (MR-proADM) is used instead of ADM as a biological indicator because ADM is rapidly degraded, and MR-proADM is released at the same rate as ADM. ADM reduces endothelial permeability and promotes endothelial stability. Endothelial dysfunction is responsible for multiple organ failure in sepsis and COVID-19 patients. Therefore, ADM may be an important molecule for improving the severity associated with sepsis and COVID-19. This review focuses on the current knowledge of PCT and ADM in sepsis and COVID-19.

Respiratory multiplex PCR and procalcitonin to reduce antibiotic exposure in severe SARS-CoV-2 pneumonia: a multicentre randomized controlled trial

OBJECTIVES

We aimed at assessing the efficacy and safety on antibiotic exposure of a strategy combining a respiratory multiplex PCR (mPCR) with enlarged panel and daily procalcitonin (PCT) measurements, as compared with a conventional strategy, in adult patients who were critically ill with laboratory-confirmed SARS-CoV-2 pneumonia.

METHODS

This multicentre, parallel-group, open-label, randomized controlled trial enrolled patients admitted to 13 intensive care units (ICUs) in France. Patients were assigned (1:1) to the control strategy, in which antibiotic streamlining remained at the discretion of the physicians, or interventional strategy, consisting of using mPCR and daily PCT measurements within the first 7 days of randomization to streamline initial antibiotic therapy, with antibiotic continuation encouraged when PCT was >1 ng/mL and discouraged if < 1 ng/mL or decreased by 80% from baseline. All patients underwent conventional microbiological tests and cultures. The primary end point was antibiotic-free days at day 28.

RESULTS

Between April 20th and November 23rd 2020, 194 patients were randomized, of whom 191 were retained in the intention-to-treat analysis. Respiratory bacterial co-infection was detected in 48.4% (45/93) and 21.4% (21/98) in the interventional and control group, respectively. The number of antibiotic-free days was 12.0 (0.0; 25.0) and 14.0 (0.0; 24.0) days, respectively (difference, -2.0, (95% CI, -10.6 to 6.6), p=0.89). Superinfection rates were high (51.6% and 48.5%, respectively). Mortality rates and ICU lengths of stay did not differ between groups.

DISCUSSION

In severe SARS-CoV-2 pneumonia, the mPCR/PCT algorithm strategy did not affect 28-day antibiotics exposure nor the major clinical outcomes, as compared with routine practice.

The Role of Biomarkers in Influenza and COVID-19 Community-Acquired Pneumonia in Adults

Pneumonia is a growing problem worldwide and remains an important cause of morbidity, hospitalizations, intensive care unit admission and mortality. Viruses are the causative agents in almost a fourth of cases of community-acquired pneumonia (CAP) in adults, with an important representation of influenza virus and SARS-CoV-2 pneumonia. Moreover, mixed viral and bacterial pneumonia is common and a risk factor for severity of disease. It is critical for clinicians the early identification of the pathogen causing infection to avoid inappropriate antibiotics, as well as to predict clinical outcomes. It has been extensively reported that biomarkers could be useful for these purposes. This review describe current evidence and provide recommendations about the use of biomarkers in influenza and SARS-CoV-2 pneumonia, focusing mainly on procalcitonin (PCT) and C-reactive protein (CRP). Evidence was based on a qualitative analysis of the available scientific literature (meta-analyses, randomized controlled trials, observational studies and clinical guidelines). Both PCT and CRP levels provide valuable information about the prognosis of influenza and SARS-CoV-2 pneumonia. Additionally, PCT levels, considered along with other clinical, radiological and laboratory data, are useful for early diagnosis of mixed viral and bacterial CAP, allowing the proper management of the disease and adequate antibiotics prescription. The authors propose a practical PCT algorithm for clinical decision-making to guide antibiotic initiation in cases of influenza and SARS-CoV-2 pneumonia. Further well-design studies are needed to validate PCT algorithm among these patients and to confirm whether other biomarkers are indeed useful as diagnostic or prognostic tools in viral pneumonia.

Serum procalcitonin level is independently associated with mechanical ventilation and case-fatality in hospitalized COVID-19-positive US veterans-A potential marker for disease severity

The Coronavirus-19 disease (COVID-19) has claimed over 6.8 million lives since first being reported in late 2019. The virus that causes COVID-19 disease is highly contagious and spreads rapidly. To date, there are no approved prognostic tools that could predict why some patients develop severe or fatal disease outcomes. Early COVID-19 studies found an association between procalcitonin (PCT) and hospitalization or duration of mechanical ventilation and death but were limited by the cohort sizes. Therefore, this study was designed to confirm the associations of PCT with COVID-19 disease severity outcomes in a large cohort. For this retrospective data analysis study, 27,154 COVID-19-positive US veterans with post-infection PCT laboratory test data and their disease severity outcomes were accessed using the VA electronic healthcare data. Cox regression models were used to test the association between serum PCT levels and disease outcomes while controlling for demographics and relevant confounding variables. The models demonstrated increasing disease severity (ventilation and death) with increasing PCT levels. For PCT serum levels above 0.20 ng/ml, the unadjusted risk increased nearly 2.3-fold for mechanical ventilation (hazard ratio, HR, 2.26, 95%CI: 2.11-2.42) and in-hospital death (HR, 2.28, 95%CI: 2.16-2.41). Even when adjusted for demographics, diabetes, pneumonia, antibiotic use, white blood cell count, and serum C-reactive protein levels, the risks remained relatively high for mechanical ventilation (HR, 1.80, 95%CI: 1.67-1.94) and death (HR, 1.76, 95%CI: 1.66-1.87). These data suggest that higher PCT levels have independent associations with ventilation and in-hospital death in veterans with COVID-19 disease, validating previous findings. The data suggested that serum PCT level may be a promising prognostic tool for COVID-19 severity assessment and should be further evaluated in a prospective clinical trial.

Updates in the management of respiratory virus infections in ICU patients: revisiting the non-SARS-CoV-2 pathogens

INTRODUCTION

Although viruses are an underestimated cause of community-acquired pneumonias (CAP) and hospital-acquired pneumonias (HAP)/ventilator-associated pneumonias (VAP) in intensive care unit (ICU) patients, they have an impact on morbidity and mortality.

AREAS COVERED

In this perspective article, we discuss the available data regarding the management of severe influenza CAP and herpesviridae HAP/VAP. We review diagnostic and therapeutic strategies in order to give clear messages and address unsolved questions.

EXPERT OPINION

Influenza CAP affects yearly thousands of people; however, robust data regarding antiviral treatment in the most critical forms are scarce. While efficacy of oseltamivir has been investigated in randomized controlled trials (RCT) in uncomplicated influenza, only observational data are available in ICU patients. Herpesviridae are an underestimated cause of HAP/VAP in ICU patients. Whilst incidence of herpesviridae identification in samples from lower respiratory tract of ICU patients is relatively high (from 20% to 50%), efforts should be made to differentiate local reactivation from true lung infection. Only few randomized controlled trials evaluated the efficacy of antiviral treatment in herpesviridae reactivation/infection in ICU patients and all were exploratory or negative. Further studies are needed to evaluate the impact of such treatment in specific populations.

The Association between Admission Procalcitonin Level and The Severity of COVID-19 Pneumonia: A Retrospective Cohort Study

Background and Objectives: An elevated procalcitonin level has classically been linked to bacterial infections. Data on the association between elevated procalcitonin and the outcome of coronavirus disease 2019 (COVID-19) are conflicting. Some linked it to associated bacterial co-infections, while others correlated the elevation with disease severity without coexisting bacterial infections. We aimed to investigate the association between high procalcitonin and the severity of COVID-19. Materials and Methods: Hospitalized patients with confirmed COVID-19 pneumonia were divided into two groups: the normal-procalcitonin group and the high-procalcitonin group (>0.05 ng/mL). Patients with concomitant bacterial infections on admission were excluded. The primary outcomes were the need for intensive care unit (ICU) admission, progression to invasive mechanical ventilation (IMV), and in-hospital 28-day mortality. Results: We included 260 patients in the normal procalcitonin group and 397 patients in the high procalcitonin group. The mean age was 55 years and 49% were females. A higher number of patients in the elevated procalcitonin group required ICU admission (32.7% vs. 16.2%, p < 0.001) and IMV (27.2% vs. 13.5%, p < 0.001). In-hospital mortality was significantly higher in the elevated procalcitonin group (18.9% vs. 8.5%, p < 0.001). After adjusting for other covariates, procalcitonin > 0.05 ng/mL was an independent predictor of progression to IMV (OR, 1.71; 95% CI, 1.08−2.71; p = 0.022), ICU admission (OR, 1.73; 95% CI, 1.13−2.66; p = 0.011), and in-hospital mortality (OR, 1.99; 95% CI, 1.14−3.47; p = 0.015). An elevated procalcitonin level was the strongest predictor of in-hospital mortality. Conclusions: Measurement of procalcitonin can have a prognostic role among COVID-19 patients. The admission procalcitonin level can identify patients at risk of ICU admission, progression to IMV, and in-hospital mortality.

Procalcitonin as a predictive marker in COVID-19: A systematic review and meta-analysis

Background

Coronavirus disease 2019 has emerged as a global pandemic causing millions of critical cases and deaths. Early identification of at-risk patients is crucial for planning triage and treatment strategies.

Methods and findings

We performed this systematic review and meta-analysis to determine the pooled prognostic significance of procalcitonin in predicting mortality and severity in patients with COVID-19 using a robust methodology and clear clinical implications.

Design

We used Preferred Reporting Items for Systematic Reviews and Meta-Analyses and Cochrane Handbook for Systematic Reviews of Interventions guidelines. We included thirty-two prospective and retrospective cohort studies involving 13,154 patients.

Results

The diagnostic odds ratio of procalcitonin for predicting mortality were estimated to be 11 (95% CI: 7 to 17) with sensitivity, specificity, and summary area under the curveof 0.83 (95% CI: 0.70 to 0.91), 0.69 (95% CI: 0.58 to 0.79), and 0.83 (95% CI: 0.79 to 0.86) respectively. While for identifying severe cases of COVID-19, the odds ratio was 8.0 (95% CI 5.0 to 12.0) with sensitivity, specificity, and summary area under the curve of 0.73 (95% CI 0.67 to 0.78), 0.74 (0.66 to 0.81), and 0.78 (95% CI 0.74 to 0.82) respectively.

Conclusion

Procalcitonin has good discriminatory power for predicting mortality and disease severity in COVID-19 patients. Therefore, procalcitonin measurement may help identify potentially severe cases and thus decrease mortality by offering early aggressive treatment.

Procalcitonin Is Not a Reliable Biomarker of Bacterial Coinfection in People With Coronavirus Disease 2019 Undergoing Microbiological Investigation at the Time of Hospital Admission

Admission procalcitonin measurements and microbiology results were available for 1040 hospitalized adults with coronavirus disease 2019 (from 48 902 included in the International Severe Acute Respiratory and Emerging Infections Consortium World Health Organization Clinical Characterisation Protocol UK study). Although procalcitonin was higher in bacterial coinfection, this was neither clinically significant (median [IQR], 0.33 [0.11-1.70] ng/mL vs 0.24 [0.10-0.90] ng/mL) nor diagnostically useful (area under the receiver operating characteristic curve, 0.56 [95% confidence interval, .51-.60]).

Nonutility of procalcitonin for diagnosing bacterial pneumonia in COVID-19

Patients hospitalized with COVID-19 are at significant risk for superimposed bacterial pneumonia. However, diagnosing superinfection is challenging due to its clinical resemblance to severe COVID-19. We therefore evaluated whether the immune biomarker, procalcitonin, could facilitate the diagnosis of bacterial superinfection. To do so, we identified 185 patients with severe COVID-19 who underwent lower respiratory culture; 85 had superinfection. Receiver operating characteristic curve analysis showed that procalcitonin at the time of culture was incapable of distinguishing patients with bacterial infection (AUC, 0.52). We conclude that static measurement of procalcitonin does not aid in the diagnosis of superinfection in severe COVID-19.

New testing guidelines for community-acquired pneumonia

PURPOSE OF REVIEW

The purpose of this article is to review diagnostic testing recommendations outlined in the current American Thoracic Society (ATS)/Infectious Diseases Society of America (IDSA) community-acquired pneumonia (CAP) guideline and the 2021 ATS guideline for noninfluenza respiratory viruses.

RECENT FINDINGS

Diagnostic testing in CAP with gram stain, lower respiratory and blood cultures, Streptococcal and Legionella urinary antigens are not routinely recommended unless identified as severe CAP or with risk factors for Methicillin-resistant Staphylococcus aureus (MRSA) or Pseudomonas aeruginosa infection. Influenza virus testing remains a strong recommendation during periods of community viral spread.An additional 2021 ATS clinical practice guideline reviewed the use of molecular testing for noninfluenza viral pathogens in adults with suspected CAP and recommended testing in those hospitalized with severe CAP and/or various immunocompromising conditions.

SUMMARY

Diagnostic testing remains an important component of confirming and treating CAP. The CAP guideline includes recommendations surrounding diagnostic testing with lower respiratory gram stain and culture, blood cultures, Legionella and Pneumococcal urinary antigen, influenza viral testing and serum procalcitonin.There is a strong recommendation to obtain influenza virus testing during periods of community spread. However, the use of other diagnostics such as gram stain, lower respiratory and blood culture, and urinary antigen testing are dependent on severity of illness and whether a patient has been identified as having strong risk factors for MRSA or P. aeruginosa infection. The 2021 ATS clinical practice document did not routinely recommend testing noninfluenza respiratory viruses unless identified as having severe CAP and/or various immunocompromising conditions.

High procalcitonin levels associated with increased intensive care unit admission and mortality in patients with a COVID-19 infection in the emergency department

Background

Patients with a severe COVID-19 infection often require admission at an intensive care unit (ICU) when they develop acute respiratory distress syndrome (ARDS). Hyperinflammation plays an important role in the development of ARDS in COVID-19. Procalcitonin (PCT) is a biomarker which may be a predictor of hyperinflammation. When patients with COVID-19 are in the emergency department (ED), elevated PCT levels could be associated with severe COVID-19 infections. The goal of this study is to investigate the association between PCT levels and severe COVID-19 infections in the ED.

Methods

This was a retrospective cohort study including patients with a confirmed COVID-19 infection who visited the ED of Erasmus Medical Center in Rotterdam, the Netherlands, between March and December 2020. The primary outcome was a severe COVID-19 infection, which was defined as patients who required ICU admission, all cause in-hospital mortality and mortality within 30 days after hospital discharge. PCT levels were measured during the ED visit. We used logistic regression to calculate the odds ratio (OR) with 95% confidence interval (95% CI) and corresponding area under the curve (AUC) of PCT on a severe COVID-19 infection, adjusting for bacterial coinfections, age, sex, comorbidities, C-reactive protein (CRP) and D-dimer.

Results

A total of 332 patients were included in the final analysis of this study, of which 105 patients reached the composite outcome of a severe COVID-19 infection. PCT showed an unadjusted OR of 4.19 (95%CI: 2.52–7.69) on a severe COVID-19 infection with an AUC of 0.82 (95% CI: 0.76–0.87). Corrected for bacterial coinfection, the OR of PCT was 4.05 (95% CI: 2.45–7.41). Adjusted for sex, bacterial coinfection, age any comorbidity, CRP and D-dimer, elevated PCT levels were still significantly associated with a severe COVID-19 infection with an adjusted OR of 2.11 (95% CI: 1.36–3.61). The AUC of this multivariable model was 0.85 (95%CI: 0.81–0.90).

Conclusion

High PCT levels are associated with high rates of severe COVID-19 infections in patients with a COVID-19 infection in the ED. The routine measurement of PCT in patients with a COVID-19 infection in the ED may assist physicians in the clinical decision making process regarding ICU disposition.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12879-022-07144-5.

Is cardiac Troponin I Considered as A Predictor of In-hospital Mortality among COVID-19 Patients? A Retrospective Cohort Study

Objective:

To describe the levels of troponin I in COVID-19 patients and its role in the prediction of their in-hospital mortality as a cardiac biomarker.

Methods:

The current retrospective cohort study was performed on the clinical records of 649 COVID-19-related hospitalized cases with at leat one positive polymerase chain reaction (PCR) test in Tehran, Iran from February 2020 to early June 2020. The on admission troponin I level divided into two groups of ≤0.03ng/mL (normal) and >0.03ng/mL (abnormal). The adjusted COX-regression model was used to determine the relationship between the studied variables and patient’s in-hospital mortality.

Results:

In this study, the median age of subjects was 65 years (54.8% men) and 29.53% of them had abnormal troponin I levels. Besides, the in-hospital mortality rate among patients with abnormal troponin I levels was found to be 51.56%; whereas, patients with normal levels exhibited 18.82% mortality. Also, the multivariable analysis indicated that the risk of death among hospitalized COVID-19 patients displaying abnormal troponin I levels was 67% higher than those with normal troponin I levels (Hazard ratio=1.67, 95% confidence interval=1.08-2.56, p=0.019).

Conclusion:

It seems that troponin I is one of the important factors related to in-hospital mortality of COVID-19 patients. Next, due to the high prevalence of cardiac complications in these patients, it is highly suggested to monitor and control cardiac biomarkers along with other clinical factors upon the patient’s arrival at the hospital.

Management of Severe Influenza

Influenza infection causes severe illness in 3 to 5 million people annually, with up to an estimated 650,000 deaths per annum. As such, it represents an ongoing burden to health care systems and human health. Severe acute respiratory infection can occur, resulting in respiratory failure requiring intensive care support. Herein we discuss diagnostic approaches, including development of CLIA-waived point of care tests that allow rapid diagnosis and treatment of influenza. Bacterial and fungal coinfections in severe influenza pneumonia are associated with worse outcomes, and we summarize the approach and treatment options for diagnosis and treatment of bacterial and Aspergillus coinfection. We discuss the available drug options for the treatment of severe influenza, and treatments which are no longer supported by the evidence base. Finally, we describe the supportive management and ventilatory approach to patients with respiratory failure as a result of severe influenza in the intensive care unit.

A close-up view of dynamic biomarkers in the setting of COVID-19: Striking focus on cardiovascular system

Based on the recent reports, cardiovascular events encompass a large portion of the mortality caused by the COVID‐19 pandemic, which drawn cardiologists into the management of the admitted ill patients. Given that common laboratory values may provide key insights into the illness caused by the life‐threatening SARS‐CoV‐2 virus, it would be more helpful for screening, clinical management and on‐time therapeutic strategies. Commensurate with these issues, this review article aimed to discuss the dynamic changes of the common laboratory parameters during COVID‐19 and their association with cardiovascular diseases. Besides, the values that changed in the early stage of the disease were considered and monitored during the recovery process. The time required for returning biomarkers to basal levels was also discussed. Finally, of particular interest, we tended to abridge the latest updates regarding the cardiovascular biomarkers as prognostic and diagnostic criteria to determine the severity of COVID‐19.

Clinical utility of procalcitonin and its association with pathogenic microorganisms

In this review, we summarize the relationship of PCT with pathogens, evaluate the clinical utility of PCT in the diagnosis of clinical diseases, condition monitoring and evaluation, and guiding medical decision-making, and explore current knowledge on the mechanisms by which pathogens cause changes in PCT levels. The lipopolysaccharides of the microorganisms stimulate cytokine production in host cells, which in turn stimulates production of serum PCT. Pathogens have different virulence mechanisms that lead to variable host inflammatory responses, and differences in the specific signal transduction pathways result in variable serum PCT concentrations. The mechanisms of signal transduction have not been fully elucidated. Further studies are necessary to ascertain the PCT fluctuation range of each pathogen. PCT levels are helpful in distinguishing between certain pathogens, in deciding if antibiotics are indicated, and in monitoring response to antibiotics.

Informing antimicrobial management in the context of COVID-19: understanding the longitudinal dynamics of C-reactive protein and procalcitonin

Background

To characterise the longitudinal dynamics of C-reactive protein (CRP) and Procalcitonin (PCT) in a cohort of hospitalised patients with COVID-19 and support antimicrobial decision-making.

Methods

Longitudinal CRP and PCT concentrations and trajectories of 237 hospitalised patients with COVID-19 were modelled. The dataset comprised of 2,021 data points for CRP and 284 points for PCT. Pairwise comparisons were performed between: (i) those with or without significant bacterial growth from cultures, and (ii) those who survived or died in hospital.

Results

CRP concentrations were higher over time in COVID-19 patients with positive microbiology (day 9: 236 vs 123 mg/L, p < 0.0001) and in those who died (day 8: 226 vs 152 mg/L, p < 0.0001) but only after day 7 of COVID-related symptom onset. Failure for CRP to reduce in the first week of hospital admission was associated with significantly higher odds of death. PCT concentrations were higher in patients with COVID-19 and positive microbiology or in those who died, although these differences were not statistically significant.

Conclusions

Both the absolute CRP concentration and the trajectory during the first week of hospital admission are important factors predicting microbiology culture positivity and outcome in patients hospitalised with COVID-19. Further work is needed to describe the role of PCT for co-infection. Understanding relationships of these biomarkers can support development of risk models and inform optimal antimicrobial strategies.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12879-021-06621-7.

Antimicrobial stewardship in the ICU in COVID times: the known unknowns

Since the start of the COVID-19 pandemic, there has been concern about the concomitant rise of antimicrobial resistance. While bacterial co-infections seem rare in COVID-19 patients admitted to hospital wards and intensive care units (ICUs), an increase in empirical antibiotic use has been described. In the ICU setting, where antibiotics are already abundantly—and often inappropriately—prescribed, the need for an ICU-specific antimicrobial stewardship programme is widely advocated. Apart from essentially warning against the use of antibacterial drugs for the treatment of a viral infection, other aspects of ICU antimicrobial stewardship need to be considered in view of the clinical course and characteristics of COVID-19. First, the distinction between infectious and non-infectious (inflammatory) causes of respiratory deterioration during an ICU stay is difficult, and the much-debated relevance of fungal and viral co-infections adds to the complexity of empirical antimicrobial prescribing. Biomarkers such as procalcitonin for the decision to start antibacterial therapy for ICU nosocomial infections seem to be more promising in COVID-19 than non-COVID-19 patients. In COVID-19 patients, cytomegalovirus reactivation is an important factor to consider when assessing patients infected with SARS-CoV-2 as it may have a role in modulating the patient immune response. The diagnosis of COVID-19-associated invasive aspergillosis is challenging because of the lack of sensitivity and specificity of the available tests. Furthermore, altered pharmacokinetic/pharmacodynamic properties need to be taken into account when prescribing antimicrobial therapy. Future research should now further explore the ‘known unknowns’, ideally with robust prospective study designs.

Coinfection of Parvovirus B19 with Influenza A/H1N1 Causes Fulminant Myocarditis and Pneumonia. An Autopsy Case Report

Parvovirus-B19 (PVB19) is a frequent causative agent of myocarditis. For unclear reasons, viral reactivation can cause acute myocarditis, a leading cause of sudden death in the young. Influenza A/H1N1(2009) virus (IAV/H1N1) is known for causing flu/pneumonia, but the heart is rarely involved. Co-infections of cardiotropic viruses are rarely reported and the mechanisms of viral interactions remain unknown. A 5-year old girl had a flu-like syndrome, when she suddenly presented with a respiratory distress and cardiac arrest. At autopsy, the lungs were found haemorrhagic. Lungs’ histology showed severe bronchiolitis, diffuse haemorrhagic necrosis, and mononuclear inflammation. In the heart, a moderate inflammation was found with no necrosis. IAV/H1N1 was detected in nasal and tracheal swabs, lungs, and the heart. The viral load was high in the lungs, but low in the heart. PVB19 was detected in the heart with a high viral load. Viral co-infection increases the risk of severe outcome but the mechanisms of interaction between viruses are poorly understood. In our case, viral loads suggested a reactivated PVB19-induced acute myocarditis during an IAV/H1N1 pneumonia. Viral interactions may involve an IAV/H1N1-induced cytokine storm, with a fulminant fatal outcome. Clinically, our case shows the importance of investigating inflammatory pathways as therapeutic targets.

Differentiating multisystem inflammatory syndrome in children: a single-centre retrospective cohort study

OBJECTIVE

Features of multisystem inflammatory syndrome in children (MIS-C) overlap with other febrile illnesses, hindering prompt and accurate diagnosis. The objectives of this study were to identify clinical and laboratory findings that distinguished MIS-C from febrile illnesses in which MIS-C was considered but ultimately excluded, and to examine the diseases that most often mimicked MIS-C in a tertiary medical centre.

STUDY DESIGN

We identified all children hospitalised with fever who were evaluated for MIS-C at our centre and compared clinical signs and symptoms, SARS-CoV-2 status and laboratory studies between those with and without MIS-C. Multivariable logistic LASSO (least absolute shrinkage and selection operator) regression was used to identify the most discriminative presenting features of MIS-C.

RESULTS

We identified 50 confirmed MIS-C cases (MIS-C⁺) and 68 children evaluated for, but ultimately not diagnosed with, MIS-C (MIS-C^-). In univariable analysis, conjunctivitis, abdominal pain, fatigue, hypoxaemia, tachypnoea and hypotension at presentation were significantly more common among MIS-C⁺ patients. MIS-C⁺ and MIS-C^- patients had similar elevations in C-reactive protein (CRP), but were differentiated by thrombocytopenia, lymphopenia, and elevated ferritin, neutrophil/lymphocyte ratio, BNP and troponin. In multivariable analysis, predictors of MIS-C included age, neutrophil/lymphocyte ratio, platelets, conjunctivitis, oral mucosa changes, abdominal pain and hypotension.

CONCLUSIONS

Among hospitalised children undergoing evaluation for MIS-C, children with MIS-C were older, more likely to present with conjunctivitis, oral mucosa changes, abdominal pain and hypotension, and had higher neutrophil/lymphocyte ratios and lower platelet counts. These data may be helpful for discrimination of MIS-C from other febrile illnesses, including bacterial lymphadenitis and acute viral infection, with overlapping features.

Elevated Procalcitonin Is Positively Associated with the Severity of COVID-19: A Meta-Analysis Based on 10 Cohort Studies

Background and Objectives: Procalcitonin (PCT) is positively associated with the severity of COVID-19 (including severe, critical, or fatal outcomes), but some of the confounding factors are not considered. The aim of this meta-analysis was to estimate the adjusted relationship between elevated procalcitonin on admission and the severity of COVID-19. Materials and Methods: We searched 1805 articles from PubMed, Web of Science, and Embase databases up to 2 April 2021. The articles were selected which reported the adjusted relationship applying multivariate analysis between PCT and the severity of COVID-19. The pooled effect estimate was calculated by the random-effects model. Results: The meta-analysis included 10 cohort studies with a total of 7716 patients. Patients with elevated procalcitonin on admission were at a higher risk of severe and critical COVID-19 (pooled effect estimate: 1.77, 95% confidence interval (CI): 1.38–2.29; I² = 85.6%, p < 0.001). Similar results were also observed in dead patients (pooled effect estimate: 1.77, 95% CI: 1.36–2.30). After adjusting for diabetes, the positive association between PCT and the severity of COVID-19 decreased. Subgroup analysis revealed heterogeneity between studies and sensitivity analysis showed that the results were robust. There was no evidence of publication bias by Egger’s test (p = 0.106). Conclusions: Higher procalcitonin is positively associated with the severity of COVID-19, which is a potential biomarker to evaluate the severity of COVID-19 and predict the prognosis.

Early Bacterial Identification Among Intubated Patients with COVID-19 or Influenza Pneumonia: A European Multicenter Comparative Cohort Study

Rationale: Early empirical antimicrobial treatment is frequently prescribed to critically ill patients with coronavirus disease (COVID-19) based on Surviving Sepsis Campaign guidelines.

Objectives: We aimed to determine the prevalence of early bacterial identification in intubated patients with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pneumonia, as compared with influenza pneumonia, and to characterize its microbiology and impact on outcomes.

Methods: A multicenter retrospective European cohort was performed in 36 ICUs. All adult patients receiving invasive mechanical ventilation >48 hours were eligible if they had SARS-CoV-2 or influenza pneumonia at ICU admission. Bacterial identification was defined by a positive bacterial culture within 48 hours after intubation in endotracheal aspirates, BAL, blood cultures, or a positive pneumococcal or legionella urinary antigen test.

Measurements and Main Results: A total of 1,050 patients were included (568 in SARS-CoV-2 and 482 in influenza groups). The prevalence of bacterial identification was significantly lower in patients with SARS-CoV-2 pneumonia compared with patients with influenza pneumonia (9.7 vs. 33.6%; unadjusted odds ratio, 0.21; 95% confidence interval [CI], 0.15–0.30; adjusted odds ratio, 0.23; 95% CI, 0.16–0.33; P < 0.0001). Gram-positive cocci were responsible for 58% and 72% of coinfection in patients with SARS-CoV-2 and influenza pneumonia, respectively. Bacterial identification was associated with increased adjusted hazard ratio for 28-day mortality in patients with SARS-CoV-2 pneumonia (1.57; 95% CI, 1.01–2.44; P = 0.043). However, no significant difference was found in the heterogeneity of outcomes related to bacterial identification between the two study groups, suggesting that the impact of coinfection on mortality was not different between patients with SARS-CoV-2 and influenza.

Conclusions: Bacterial identification within 48 hours after intubation is significantly less frequent in patients with SARS-CoV-2 pneumonia than patients with influenza pneumonia.Clinical trial registered with www.clinicaltrials.gov (NCT 04359693).

A Rare Case of Dengue Encephalitis with Raised Procalcitonin

BACKGROUND Dengue virus is a common arbovirus with uncertain neurotropism. Dengue encephalitis is a rare but fatal manifestation of severe dengue. Diagnosis requires high clinical suspicion. It should be routinely considered in patients with encephalopathy, especially in countries where dengue virus is endemic. Unlike other forms of severe dengue, the typical warning signs and biochemical derangements are not reliable markers for dengue encephalitis. Alternative biochemical markers of dengue encephalitis are needed. CASE REPORT We present a case of dengue encephalitis with distinctly raised procalcitonin (13.2 μg/L), in the absence of the typical warning signs and biochemical derangements of severe dengue. The patient was a 65-year-old man with fever and sudden loss of consciousness in the absence of other localizing signs/symptoms. Inflammatory markers were raised, with findings of leptomeningeal enhancement on brain computed tomography suggestive of meningoencephalitis. Septic workup was unremarkable (normal renal and liver functions, negative blood and urine cultures). The typical neurotropic microorganisms were not detected in the cerebrospinal fluid. On day 4 of admission, the patient reported abdominal pain and hematuria with a new onset of bicytopenia. Subsequent investigations for dengue infection were positive for serum dengue NS1 antigen and dengue RNA (type 2 strain) in cerebrospinal fluid, confirming the diagnosis of dengue encephalitis. The patient was managed supportively and experienced full clinical recovery. CONCLUSIONS Dengue encephalitis is a rare condition with nonspecific biochemical and imaging abnormalities. We demonstrated that a raised procalcitonin level can occur in the setting of dengue encephalitis. In endemic countries, this finding may prompt further investigations for dengue encephalitis in patients with meningoencephalitis.

Future Biomarkers for Infection and Inflammation in Febrile Children

Febrile patients, suffering from an infection, inflammatory disease or autoimmunity may present with similar or overlapping clinical symptoms, which makes early diagnosis difficult. Therefore, biomarkers are needed to help physicians form a correct diagnosis and initiate the right treatment to improve patient outcomes following first presentation or admittance to hospital. Here, we review the landscape of novel biomarkers and approaches of biomarker discovery. We first discuss the use of current plasma parameters and whole blood biomarkers, including results obtained by RNA profiling and mass spectrometry, to discriminate between bacterial and viral infections. Next we expand upon the use of biomarkers to distinguish between infectious and non-infectious disease. Finally, we discuss the strengths as well as the potential pitfalls of current developments. We conclude that the use of combination tests, using either protein markers or transcriptomic analysis, have advanced considerably and should be further explored to improve current diagnostics regarding febrile infections and inflammation. If proven effective when combined, these biomarker signatures will greatly accelerate early and tailored treatment decisions.

Respiratory viral infections in the elderly

With the global over 60-year-old population predicted to more than double over the next 35 years, caring for this aging population has become a major global healthcare challenge. In 2016 there were over 1 million deaths in >70 year olds due to lower respiratory tract infections; 13-31% of these have been reported to be caused by viruses. Since then, there has been a global COVID-19 pandemic, which has caused over 2.3 million deaths so far; increased age has been shown to be the biggest risk factor for morbidity and mortality. Thus, the burden of respiratory viral infections in the elderly is becoming an increasing unmet clinical need. Particular challenges are faced due to the interplay of a variety of factors including complex multimorbidities, decreased physiological reserve and an aging immune system. Moreover, their atypical presentation of symptoms may lead to delayed necessary care, prescription of additional drugs and prolonged hospital stay. This leads to morbidity and mortality and further nosocomial spread. Clinicians currently have limited access to sensitive detection methods. Furthermore, a lack of effective antiviral treatments means there is little incentive to diagnose and record specific non-COVID-19 viral infections. To meet this unmet clinical need, it is first essential to fully understand the burden of respiratory viruses in the elderly. Doing this through prospective screening research studies for all respiratory viruses will help guide preventative policies and clinical trials for emerging therapeutics. The implementation of multiplex point-of-care diagnostics as a mainstay in all healthcare settings will be essential to understand the burden of respiratory viruses, diagnose patients and monitor outbreaks. The further development of novel targeted vaccinations as well as anti-viral therapeutics and new ways to augment the aging immune system is now also essential.The reviews of this paper are available via the supplemental material section.

Quantification of bronchoalveolar neutrophil extracellular traps and phagocytosis in murine pneumonia

The past two decades have witnessed a resurgence in neutrophil research, inspired in part by the discovery of neutrophil extracellular traps (NETs) and their myriad roles in health and disease. Within the lung, dysregulation of neutrophils and NETosis have been linked to an array of diseases including pneumonia, cystic fibrosis, acute respiratory distress syndrome (ARDS), chronic obstructive pulmonary disease (COPD), and severe asthma. However, our understanding of pathologic neutrophil responses in the lung remains incomplete. Two methodologic issues have contributed to this gap: first, an emphasis on studying neutrophils from blood rather than the lung and second, the technical difficulties of interrogating neutrophil responses in mice, which has largely restricted basic murine research to specialized laboratories. To address these limitations, we have developed a suite of techniques for studying neutrophil effector functions specifically in the mouse lung. These include ex vivo assays for phagocytosis and NETosis using bronchoalveolar neutrophils and in situ evaluation of NETosis in a murine model of pneumonia. Throughout, we have prioritized technical ease and robust, quantitative readouts. We hope these assays will help to standardize research on lung neutrophils and improve accessibility to this burgeoning field.