Biomarkers in lower respiratory tract infections

Increased plasma AACT level as an indicator of poor prognosis in patients hospitalised with community-acquired pneumonia: a multicentre prospective cohort study

BACKGROUND AND OBJECTIVE

Community-acquired pneumonia (CAP) is a common respiratory disease that frequently requires hospitalisation, and is a significant cause of death worldwide. This study aimed to evaluate the usefulness of alpha-1-antichymotrypsin (AACT) as a diagnostic and prognostic biomarker of CAP.

METHODS

We conducted a multicentre prospective cohort study in patients hospitalised with CAP. Plasma AACT levels were measured using a quantitative enzyme-linked immunosorbent assay. Receiver-operating characteristic (ROC) curves and Cox proportional hazards regression were used to assess the association between plasma AACT levels and CAP diagnosis and prognosis.

RESULTS

A total of 274 patients with CAP were enrolled in the study. AACT levels were elevated in patients with CAP, especially those with severe CAP and non-survivors. The area under the curve (AUC) of AACT and CRP for diagnosing CAP was 0.755 and 0.843. Cox regression showed that CURB-65 and AACT levels were independent predictors of 30-day mortality. ROC curves showed that plasma AACT levels had the highest accuracy for predicting acute respiratory distress syndrome (ARDS), with an AUC of 0.862. Combining AACT with Pneumonia Severity Index and CURB-65 significantly improved their predictive accuracy for predicting 30-day mortality.

CONCLUSION

Plasma AACT levels are elevated in patients with CAP, but plasma AACT level is inferior to the C-reactive protein level for diagnosing CAP. The AACT level can reliably predict the occurrence of ARDS and 30-day mortality in patients with CAP.

Decreased plasma fetuin-A level as a novel bioindicator of poor prognosis in community-acquired pneumonia: A multi-center cohort study

Background

Community-acquired pneumonia (CAP) is a respiratory disease that frequently requires hospital admission, and is a significant cause of death worldwide. Plasma fetuin-A levels were significantly lower in patients with sepsis, but data regarding CAP are scarce. This study aimed to evaluate the usefulness of fetuin-A as a prognostic biomarker of CAP.

Methods

A multicenter cohort study on CAP was conducted between January 2017 and December 2018. Demographic and clinical data were recorded for all enrolled patients. Plasma fetuin-A levels were determined using a quantitative enzyme-linked immunosorbent assay. A Cox proportional hazards regression analysis was used to analyse the effect of variables on 30-day mortality. A logistic regression analysis was performed to assess risk factors associated with severe CAP (SCAP) and 30-day mortality. A receiver operating characteristic (ROC) curve was used to verify the association between variables and CAP prognosis. Correlations were assessed using Spearman's test. Survival curves were constructed and compared using the log-rank test.

Results

A total of 283 patients with CAP were enrolled in this study. Fetuin-A levels were decreased in patients with CAP, especially in SCAP and non-survivors. A cox regression analysis showed that CURB-65 and fetuin-A levels were independent prognostic indicators of 30-day mortality. Via a multiple logistic regression analysis, plasma level of fetuin-A (<202.86 mg/L) was determined to be the strongest independent predictor of 30-day mortality considered (odds ratio, 57.365), and also was also determined to be an independent predictor of SCAP. The area under the curve (AUC) of fetuin-A for predicting 30-day mortality was 0.871, and accuracy was high (P < 0.05). Plasma fetuin-A levels were negatively correlated with WBC, NE%, Glu, CRP, PCT, CURB-65, and pneumonia severity index scores and positively correlated with albumin level. Kaplan–Meier curves showed that lower plasma levels of fetuin-A levels were associated with increased 30-day mortality levels (P < 0.0001).

Conclusion

Plasma fetuin-A levels were decreased in patients with CAP. Fetuin-A can reliably predict mortality in patients with CAP, and is a useful diagnostic indicator of SCAP.

Diagnostic performance of the Sputum Gram Stain in predicting sputum culture results for critically ill pediatric patients with pneumonia

BACKGROUND

The sputum Gram stain is an inexpensive, rapid, and convenient laboratory method that predicts the bacterial pathogens in patients with pneumonia. This study aimed to evaluate the diagnostic performance of this method in predicting sputum culture results for critically ill pediatric patients.

METHODS

From June 2008 to June 2018, patients with pneumonia with an endotracheal or a tracheostomy tube in place in the Pediatric Intensive Care Unit at Changhua Christian Hospital were enrolled retrospectively. Sputum was collected from each patient via the artificial airway for Gram stain and culture evaluations of bacterial pathogens. Mixed culture results were excluded. A successful prediction was defined as a match of the sputum Gram stain and culture results.

RESULTS

A total of 622 records were reviewed, of which 542 were analyzed. Haemophilus influenzae, Pseudomonas aeruginosa, and Streptococcus pneumoniae were the three most common pathogens found. The overall prediction success rate of the sputum Gram stain was 59.23%. The sensitivity of the method in predicting gram-negative bacilli (GNB), gram-negative cocci (GNC), and gram-positive cocci (GPC) was 0.45, 0.67, and 0.61, respectively. Its specificity in predicting GNB, GNC, and GPC was 0.87, 0.98, and 0.87, respectively. Its positive likelihood ratio in predicting GNB, GNC, and GPC was 3.46, 33.50, and 4.69, respectively. The highest prediction success rate among all pathogens was for GNC.

CONCLUSION

The sputum Gram stain had high specificity and relatively low sensitivity in predicting the bacterial pathogens in critically ill pediatric patients. Its high specificity in predicting sputum culture results means that clinicians can confidently use sputum Gram stain results to guide their antibiotic choice for treatment.

Biomarkers and clinical scoring systems in community-acquired pneumonia

Community-acquired pneumonia (CAP) is the third most common cause of death globally. Due to the complexity of CAP, it is widely accepted that, currently, clinical prognosis and diagnosis is inadequate for the assessment of the severity of the disease. With the aim to determining the initial treatment and the appropriate level of intervention, several clinical scores of severity and biomarkers have been developed. Both biomarkers and clinical scoring systems are expected to determine the different aspects of the host factor and the response to therapy, in order for physicians to be able to make an accurate benefit/risk assessment that will lead to proper diagnosis and correct prescription of antibiotics. This review aims to highlight the prognostic and diagnostic accuracy of various laboratory and clinical parameters in CAP and discuss the perspectives for the reduction of CAP mortality.

Biomarkers in Pneumonia-Beyond Procalcitonin

Pneumonia is the leading infectious cause of mortality worldwide and one of the most common lower respiratory tract infections that is contributing significantly to the burden of antibiotic consumption. Due to the complexity of its pathophysiology, it is widely accepted that clinical diagnosis and prognosis are inadequate for the accurate assessment of the severity of the disease. The most challenging task for a physician is the risk stratification of patients with community-acquired pneumonia. Herein, early diagnosis is essential in order to reduce hospitalization and mortality. Procalcitonin and C-reactive protein remain the most widely used biomarkers, while interleukin 6 has been of particular interest in the literature. However, none of them appear to be ideal, and the search for novel biomarkers that will most sufficiently predict the severity and treatment response in pneumonia has lately intensified. Although our insight has significantly increased over the last years, a translational approach with the application of genomics, metabolomics, microbiomics, and proteomics is required to better understand the disease. In this review, we discuss this rapidly evolving area and summarize the application of novel biomarkers that appear to be promising for the accurate diagnosis and risk stratification of pneumonia.

Respiratory tract virus infections in the elderly with pneumonia

BACKGROUND

In children suffering from severe lower airway illnesses, respiratory virus detection has given good prognostic information, but such reports in the elderly are scarce. Therefore, our aim was to study whether the detection of nasopharyngeal viral pathogens and conventional inflammatory markers in the frail elderly correlate to the presence, signs and symptoms or prognosis of radiographically-verified pneumonia.

METHODS

Consecutive episodes of hospital care of patients 65 years and older with respiratory symptoms (N = 382) were prospectively studied as a cohort. Standard clinical questionnaire was filled by the study physician. Laboratory analyses included PCR diagnostics of nasopharyngeal swab samples for 14 respiratory viruses, C-reactive protein (CRP) and white blood cell count (WBC). Chest radiographs were systematically analysed by a study radiologist. The length of hospital stay, hospital revisit and death at ward were used as clinical endpoints.

RESULTS

Median age of the patients was 83 years (range 76-90). Pneumonia was diagnosed in 112/382 (29%) of the studied episodes. One or more respiratory viruses were detected in 141/382 (37%) episodes and in 34/112 (30%) episodes also diagnosed with pneumonia. Pneumonia was associated with a WBC over 15 × 10⁹/L (P = .006) and a CRP value over 80 mg/l (P < .05). A virus was detected in 30% of pneumonia episodes and in 40% of non-pneumonia episodes, but this difference was not significant (P = 0.09). The presence of a respiratory virus was associated with fewer revisits to the hospital (P < .05), whereas a CRP value over 100 mg/l was associated with death during hospital stay (P < .05). Respiratory virus detections did not correlate to WBC or CRP values, signs and symptoms or prognosis of radiographically-verified pneumonia episodes.

CONCLUSION

Among the elderly with respiratory symptoms, respiratory virus detection was not associated with an increased risk of pneumonia or with a more severe clinical course of the illness. CRP and WBC remain important indicators of pneumonia, and according to our findings, pneumonia should be treated as a bacterial disease regardless of the virus findings. Our data does not support routine virus diagnostics for the elderly patients with pneumonia outside the epidemic seasons.

Combination of procalcitonin, C-reaction protein and carcinoembryonic antigens for discriminating between benign and malignant pleural effusions

Pleural effusion (PE) is a common manifestation associated with certain chest diseases. However, there is no effective diagnostic marker with high sensitivity and specificity. The aim of the present study was to evaluate the diagnostic performance of several biomarkers in the use of detecting malignant pleural disorder. One hundred and fifty patients with a specific diagnosis of exudative PE were enrolled in this study and were divided into the benign PE group (n=93) and the malignant PE group (n=57). Thoracoscopy was conducted to identify the reasons for the PE. Biomarkers in pleural fluid and in sera were determined either by microparticle enzyme immunoassay [carcinoembryonic antigen (CEA)], fluorescence immunoassay [procalcitonin (PCT)] or light-scattering turbidimetric immunoassay [C-reaction protein (CRP)]. Then, correlation analysis and receiver-operating characteristic (ROC) curve analysis individually or in combination were performed. The CRP and PCT levels were higher in benign PE than they were in malignant PE (PCT: P=0.017, P=0.032; CRP: P=0.001, P<0.001, respectively), while CEA levels were lower in benign PE than in malignant PE (CEA: P=0.001, P=0.001, respectively). During the ROC curve analysis, an optimal discrimination was identified by combining pleural CRP, pleural CEA and serum (s)PCT with an area under the curve of 0.973 (sensitivity, 98.9%; specificity, 89.5%). In the diagnosis of PE, there was no single biomarker that appeared to be adequately accurate. The combination of pleural CRP, pleural CEA and sPCT may represent an efficient diagnostic procedure for guiding the patient towards follow-up clinical treatment.

Comparison of procalcitonin, C-reactive protein, white blood cell count and clinical status in diagnosing pneumonia in patients hospitalized with acute exacerbations of COPD: A prospective observational study

Lower respiratory tract infection is the most common cause of acute exacerbations of chronic obstructive pulmonary disease (AECOPD). The aim of the present study was to compare the accuracy of procalcitonin (PCT), C-reactive protein (CRP) and white blood cell count (WBC) as single diagnostic tests and in combination with clinical signs and symptoms to diagnose pneumonia in patients hospitalized with AECOPD. This was a prospective, single centre observational study. Patients with spirometry-confirmed COPD who were hospitalized due to AECOPD were consecutively recruited at the hospital's Emergency Unit. Pneumonia was defined as a new pulmonary infiltrate on chest X-ray. The values of PCT, CRP and WBC were determined at admission. Receiver operating characteristic (ROC) curve analysis was used to study the accuracy of various diagnostic tests. Of the 113 included patients, 35 (31%) had pneumonia at admission. Area under the ROC curve (AUC) for PCT, CRP and WBC as a single test to distinguish between patients with and without pneumonia was 0.67 (95% CI 0.55-0.79), 0.73 (95% CI 0.63-0.84) and 0.67 (95% CI 0.55-0.79), respectively ( p = 0.42 for the test of difference). The AUC for a model of clinical signs and symptoms was 0.84 (95% CI 0.76-0.92). When biomarkers were added to the clinical model, the AUCs of the combined models were not significantly different from that of the clinical model alone ( p = 0.54). PCT had about the same accuracy as CRP and WBC in predicting pneumonia in patients hospitalized with AECOPD both as a single test and in combination with clinical signs and symptoms.

Transcriptomic Biomarkers to Discriminate Bacterial from Nonbacterial Infection in Adults Hospitalized with Respiratory Illness

Lower respiratory tract infection (LRTI) commonly causes hospitalization in adults. Because bacterial diagnostic tests are not accurate, antibiotics are frequently prescribed. Peripheral blood gene expression to identify subjects with bacterial infection is a promising strategy. We evaluated whole blood profiling using RNASeq to discriminate infectious agents in adults with microbiologically defined LRTI. Hospitalized adults with LRTI symptoms were recruited. Clinical data and blood was collected, and comprehensive microbiologic testing performed. Gene expression was measured using RNASeq and qPCR. Genes discriminatory for bacterial infection were identified using the Bonferroni-corrected Wilcoxon test. Constrained logistic models to predict bacterial infection were fit using screened LASSO. We enrolled 94 subjects who were microbiologically classified; 53 as “non-bacterial” and 41 as “bacterial”. RNAseq and qPCR confirmed significant differences in mean expression for 10 genes previously identified as discriminatory for bacterial LRTI. A novel dimension reduction strategy selected three pathways (lymphocyte, α-linoleic acid metabolism, IGF regulation) including eleven genes as optimal markers for discriminating bacterial infection (naïve AUC = 0.94; nested CV-AUC = 0.86). Using these genes, we constructed a classifier for bacterial LRTI with 90% (79% CV) sensitivity and 83% (76% CV) specificity. This novel, pathway-based gene set displays promise as a method to distinguish bacterial from nonbacterial LRTI.

Superiority of transcriptional profiling over procalcitonin for distinguishing bacterial from viral lower respiratory tract infections in hospitalized adults

BACKGROUND

Distinguishing between bacterial and viral lower respiratory tract infection (LRTI) remains challenging. Transcriptional profiling is a promising tool for improving diagnosis in LRTI.

METHODS

We performed whole blood transcriptional analysis in 118 patients (median age [interquartile range], 61 [50-76] years) hospitalized with LRTI and 40 age-matched healthy controls (median age, 60 [46-70] years). We applied class comparisons, modular analysis, and class prediction algorithms to identify and validate diagnostic biosignatures for bacterial and viral LRTI.

RESULTS

Patients were classified as having bacterial (n = 22), viral (n = 71), or bacterial-viral LRTI (n = 25) based on comprehensive microbiologic testing. Compared with healthy controls, statistical group comparisons (P < .01; multiple-test corrections) identified 3376 differentially expressed genes in patients with bacterial LRTI, 2391 in viral LRTI, and 2628 in bacterial-viral LRTI. Patients with bacterial LRTI showed significant overexpression of inflammation and neutrophil genes (bacterial > bacterial-viral > viral), and those with viral LRTI displayed significantly greater overexpression of interferon genes (viral > bacterial-viral > bacterial). The K-nearest neighbors algorithm identified 10 classifier genes that discriminated between bacterial and viral LRTI with a 95% sensitivity (95% confidence interval, 77%-100%) and 92% specificity (77%-98%), compared with a sensitivity of 38% (18%-62%) and a specificity of 91% (76%-98%) for procalcitonin.

CONCLUSIONS

Transcriptional profiling is a helpful tool for diagnosis of LRTI.

Performance of pro-adrenomedullin for identifying adverse outcomes in community-acquired pneumonia

BACKGROUND

We sought to evaluate the usefulness of biomarkers-procalcitonin (PCT), C-reactive protein (CRP) and proadrenomedullin (pro-ADM)-combined with prognostic scales (PSI, CURB-65 and SCAP score) for identifying adverse outcomes in patients with community-acquired pneumonia (CAP) attending at an Emergency Department (ED).

METHODS

Prospective observational study in a teaching hospital among patients with CAP. In addition to collecting data for the prognostic scales, samples were taken at the ED for assessing PCT, CRP and pro-ADM levels. We compared the prognostic accuracy of these biomarkers with severity scores to predict pneumonia related complications, using the area under the receiver operating characteristics curves (AUC), which evaluates how well the model discriminate between patients who had a pneumonia related complication or not.

RESULTS

A total of 491 patients with CAP were enrolled, 256 being admitted to the hospital and 235 treated as outpatients. Admitted patients had higher biomarker levels than outpatients (p < 0.001). The SCAP score and pro-ADM level had the best AUCs for predicting pneumonia related complications (0.83 and 0.84, respectively). Considering SCAP score plus pro-ADM level, the AUC increased significantly to 0.88. SCAP score class 0 or 1 with a pro-ADM level <0.5 ng/mL was the best indicator for selecting patients for outpatient care.

CONCLUSIONS

A new risk score combining SCAP score with pro-ADM level is useful to classify severity risk in CAP patients and hence supporting decision-making on hospital admission.

Microfluidic platforms for biomarker analysis

Biomarkers have been described as characteristics, most often molecular, that provide information about biological states, whether normal, pathological, or therapeutically modified. They hold great potential to assist diagnosis and prognosis, monitor disease, and assess therapeutic effectiveness. While a few biomarkers are routinely utilised clinically, these only reflect a very small percentage of all biomarkers discovered. Numerous factors contribute to the slow uptake of these new biomarkers, with challenges faced throughout the biomarker development pipeline. Microfluidics offers two important opportunities to the field of biomarkers: firstly, it can address some of these developmental obstacles, and secondly, it can provide the precise and complex platform required to bridge the gap between biomarker research and the biomarker-based analytical device market. Indeed, adoption of microfluidics has provided a new avenue for advancement, promoting clinical utilisation of both biomarkers and their analytical platforms. This review will discuss biomarkers and outline microfluidic platforms developed for biomarker analysis.

Serum C-reactive protein as a diagnostic biomarker in dogs with bacterial respiratory diseases

Background

C‐reactive protein (CRP) is a major acute‐phase protein in dogs. Serum concentrations are low in healthy animals, but increase rapidly after inflammatory stimuli.

Objective

The aim of the study was to investigate CRP concentrations in various respiratory diseases of dogs and to determine if CRP can be used as a biomarker in the diagnosis of bacterial respiratory diseases.

Animals

A total of 106 privately owned dogs with respiratory diseases (17 with bacterial tracheobronchitis [BTB], 20 with chronic bronchitis [CB], 20 with eosinophilic bronchopneumopathy [EBP], 12 with canine idiopathic pulmonary fibrosis [CIPF], 15 with cardiogenic pulmonary edema [CPE], and 22 with bacterial pneumonia [BP]) and 72 healthy controls.

Methods

The study was conducted as a prospective cross‐sectional observational study. CRP was measured in serum samples. Diagnosis was confirmed by clinical and laboratory findings, diagnostic imaging, and selected diagnostic methods such as cytological and microbiological analysis of respiratory samples, echocardiography, and histopathology.

Results

Dogs with BP had significantly higher CRP concentrations (median, 121 mg/L; interquartile range, 68–178 mg/L) than dogs with BTB (23, 15–38, P = .0003), CB (13, 8–14, P < .0001), EBP (5, 5–15, P < .0001), CIPF (17, 10–20, P < .0001), or CPE (19, 13–32, P < .0001) and healthy controls (14, 8–20, P < .0001). Dogs with BTB had significantly higher CRP concentrations than dogs with CB (P = .001) or EBP (P < .0001) and healthy controls (P = .029).

Conclusion and Clinical Importance

These results indicate that CRP has potential for use as an additional biomarker, especially in the diagnostics of BP.

Procalcitonin as a diagnostic marker in differentiating parapneumonic effusion from tuberculous pleurisy or malignant effusion

OBJECTIVES

Differential diagnosis of exudative pleural effusions can be difficult, despite the use of several biomarkers. Serum procalcitonin (s-PCT) is a well-known biomarker for systemic bacterial infections. However, the usefulness of pleural fluid procalcitonin (pf-PCT) in clinical practice has not been established. This study evaluated the usefulness of PCT measurements in differentiating parapneumonic effusion (PPE) from tuberculous (TB) pleurisy or malignant effusion.

DESIGN AND METHODS

Ninety eight adult patients diagnosed with exudative pleural effusion were enrolled and allocated into the PPE group (n=32), TB pleurisy group (n=40), or malignant effusion group (n=26). Both s-PCT and pf-PCT concentrations were measured at admission using an immunoluminometric assay.

RESULTS

Both s-PCT and pf-PCT were significantly increased in the PPE group compared with the TB pleurisy or malignant effusion groups (p<0.001). The optimal cut-off value for s-PCT in the diagnosis of PPE was 0.18 ng/mL (sensitivity 83.3%, specificity 81.0%). The pf-PCT cut-off value was 0.16 ng/mL (sensitivity 81.5%, specificity 72.1%). Serum PCT exhibited better diagnostic accuracy than pf-PCT, with areas under the receiver operating characteristic curves of 0.842 for s-PCT and 0.784 for pf-PCT (p=0.015). In addition, s-PCT and pf-PCT showed better diagnostic accuracy than serum C-reactive protein (p=0.005 and p=0.023, respectively).

CONCLUSIONS

Measurement of s-PCT and pf-PCT is useful in differentiating PPE from TB pleurisy and malignant effusion. Both s-PCT and pf-PCT may be useful biomarkers in the differential diagnosis of exudative pleural effusions.

Practical management problems of chronic obstructive pulmonary disease in the elderly: acute exacerbations

PURPOSE OF REVIEW

Acute exacerbations of chronic obstructive pulmonary disease (ECOPDs) have numerous causes and are associated with increased mortality and hospitalization, especially in older patients. The urgent need to identify and enable timely treatment of ECOPDs is a necessity for physicians worldwide. This review will highlight the causes and optimal combinations of available treatments for such events in older populations.

RECENT FINDINGS

The exact definition of exacerbations is lacking; however, it is agreed that such events are considered episodes of worsening of symptoms, leading to morbidity and death. The aging process is a consistent determinant for ECOPD events and is associated with worsening of COPD stages. The incidence of ECOPD rises across the worsening stages of COPD. Studies have shown that the frequency of exacerbations increases with age and correlated clinical outcomes are poorer than in younger patients. The risk of mortality has also been shown to be significantly higher after a hospital admission following an acute exacerbation. At the moment, the need to rapidly and correctly treat acute exacerbations is crucially important in the rapidly growing elderly population.

SUMMARY

ECOPDs are extremely dangerous events for older patients with severe stages of COPD. There is an urgent need to identify risk factors, identify tolerable treatment guidelines and manage acute exacerbations in older patients with COPD.