Procalcitonin and neopterin correlation with aetiology and severity of pneumonia

Elevated neopterin in tuberculosis and co-infection with HIV and the effect of treatment: A systematic review, meta-analysis, and meta-regression

BACKGROUND

Neopterin (NEO) is a marker of immune stimulation. Increased NEO levels have been associated with autoimmune diseases, infections, and malignancies. Studies of NEO alterations in tuberculosis (TB) with or without HIV co-infection show inconsistent results. Moreover, challenges exist regarding TB diagnosis in people with HIV.

METHODS

We did a systematic review and meta-analysis of studies comparing urinary, pleural, and blood NEO levels between patients with TB or HIV-TB co-infection as the case group and subjects without TB and HIV or subjects with HIV without TB as the control group, respectively.

RESULTS

Blood NEO levels in patients with active TB were higher than healthy controls, with a large effect size of 1.99. Patients with TB had higher blood NEO levels before anti-tuberculosis therapy (ATT) than after ATT for months or when treatment ended with moderate effect sizes (1.13-1.46). meta-analysis of studies of patients with HIV-TB co-infection yielded similar results, with higher blood NEO levels in patients than controls that remained significant in subgroups of studies on pulmonary TB (PTB) patients and serum NEO and higher blood NEO levels in patients before than after ATT.

CONCLUSION

Meta-analyses reveal alteration in NEO levels in different specimens, e.g., blood, urine, and pleural fluid, in patients with TB with or HIV-TB co-infection compared to the control groups. Future studies need to investigate the utility of NEO as a diagnostic/prognostic biomarker for TB. Also, cellular and molecular mechanisms linking NEO and TB remain to be addressed.

The Use of Neopterin as a Noninvasive Marker in Monitoring Diseases in Wild Chimpanzees

Pathogen analysis in wild great apes is both time- and resource-consuming. Therefore, we examined the potential use of urinary neopterin, a sensitive marker of cell-mediated immune system activation, as a disease marker and unspecific screening tool to facilitate informed pathogen analysis in great ape health monitoring. To test this, urinary neopterin was correlated to other disease markers such as sickness behaviors, fever, and urine parameters. Seasonal variation in urinary neopterin levels was investigated as well. The study encompassed noninvasively collected longitudinal data of young wild chimpanzees from the Taï National Park, Côte d´Ivoire. Relationships between disease markers were examined using a linear mixed model and a case study approach. Seasonal variation in urinary neopterin was tested using a linear mixed model. While the linear mixed model found no obvious relationship between urinary neopterin levels and other disease markers, the case study approach revealed a pattern resembling those found in humans. Urinary neopterin levels indicated seasonal immune system activation peaking in times of low ambient temperatures. We suggest the use of urinary neopterin as an unspecific screening tool in great ape health monitoring to identify relevant samples, individuals, and time periods for selective pathogen analysis and zoonotic risk assessment.

Urinary neopterin levels increase and predict survival during a respiratory outbreak in wild chimpanzees (Taï National Park, Côte d'Ivoire)

Monitoring immune system activation of wild animals has garnered increasing interest within the field of ecological immunology, leading to an urgent need for non-invasive biomarkers measuring these changes. Urinary neopterin, a marker of the cell-mediated immune response, is validated as an immune-related biomarker in captive and laboratory animals. However, wild animals naturally host higher and chronic pathogen loads. Therefore, detection and quantification of additional infections via neopterin might not be possible against the background of a chronically challenged immune system. To assess the suitability of urinary neopterin in wild animals, we measured neopterin corrected for specific gravity with an enzyme immunoassay in 185 samples collected before, during and after a respiratory disease outbreak in 28 individuals from a group of wild chimpanzees (Taï National Park, Côte d'Ivoire). Urinary neopterin levels were significantly higher during periods when individuals showed respiratory symptoms versus before and after the outbreak. Furthermore, urinary neopterin levels were significantly higher in individuals that died, with higher levels already apparent before the outbreak, suggesting individuals may have an already activated immune system. Measuring urinary neopterin levels, with other biomarkers of energetic condition, stress challenges, and reproduction will contribute towards a deeper understanding of life-history trade-offs in wild animals.

Influence of pathogen and focus of infection on procalcitonin values in sepsis patients with bacteremia or candidemia

Background

This study aimed to evaluate the accuracy of procalcitonin (PCT) serum concentrations to diagnose Gram-negative bacteremia and the association of PCT serum concentrations with more specific pathogens and the focus of infection.

Methods

Secondary analysis of the prospectively collected patient-level dataset from a cluster randomized quality improvement trial was performed. The trial included sepsis patients with organ dysfunction treated in the participating intensive care units from 2011 to 2015. Test performance for the prediction of Gram-negative bacteremia was assessed by receiver operating curve analysis. Independent effects of specific pathogen groups and foci of infection on PCT concentrations were assessed by linear logistic regression models.

Results

Blood cultures (BC) and PCT concentrations had been taken in 4858 of 6561 documented patients. PCT was significantly higher in Gram-negative bacteremia compared to Gram-positive bacteremia or candidemia (p < 0.001). The area under the curve was 0.72 (95% confidence interval 0.71–0.74) for the prediction of Gram-negative bacteremia compared to all other blood culture results including negative blood cultures. The optimized cutoff value was 10 ng/ml (sensitivity 69%, specificity 35%). PCT differed significantly between specific groups of pathogens (p < 0.001) with highest concentrations in Escherichia coli, Streptococcus species and other Enterobacteriaceae. PCT was highest in urogenital followed by abdominal infection and lowest in respiratory infection (p < 0.001). In a linear regression model, Streptococci, E. coli and other Enterobacteriaceae detected from BC were associated with three times higher PCT values. Urogenital or abdominal foci of infection were associated with twofold increased PCT values independent of the pathogen.

Conclusions

Serum PCT concentrations are higher in patients with Gram-negative bacteremia than in patients with Gram-positive bacteremia or candidemia. However, the discriminatory power of this difference is too low to guide therapeutic decisions. Variations in PCT serum concentrations are not determined solely by Gram-negative or Gram-positive bacteria but are also affected by distinct groups of pathogens and different foci of infection.

Trial registration

ClinicalTrials.gov, NCT01187134. Registered on 23 August 2010.

Electronic supplementary material

The online version of this article (10.1186/s13054-018-2050-9) contains supplementary material, which is available to authorized users.

Stable-State Midrange-Proadrenomedullin Level Is a Strong Predictor of Mortality in Patients With COPD

BACKGROUND

Midrange-proadrenomedullin (MR-proADM) has been shown to be elevated in patients hospitalized for an acute exacerbation of COPD (AECOPD) and in patients with community-acquired pneumonia. When measured during AECOPDs, MR-proADM has also been shown to be a predictor of mortality. We hypothesized that MR-proADM levels measured in a stable state could also predict mortality.

METHODS

We included 181 patients in whom we had paired plasma samples for MR-proADM determinations during a stable state and at hospitalization for an AECOPD when they also produced sputum. Time to death or censoring was compared between patients with MR-proADM above or below the median of 0.71 nmol/L. The predictive value of MR-proADM for survival was determined by calculating the C statistic.

RESULTS

Patients with COPD and MR-proADM levels > 0.71 nmol/L in the stable state had a threefold-higher risk of dying than did patients with MR-proADM levels < 0.71 nmol/L (hazard ratio, 2.98 [95% CI, 1.51-5.90]; C statistic, 0.76). The corrected OR for 1-year mortality was 8.90 (95% CI, 1.94-44.6) in patients with high MR-proADM levels measured in the stable state, compared with patients with low levels measured in the stable state.

CONCLUSIONS

MR-proADM measured in the stable state appeared to be a strong predictor of mortality in patients with COPD. MR-proADM is far easier to measure than other predictors of mortality in COPD, such as BMI, airflow obstruction, dyspnea, and exercise capacity score.

Bacteria in the respiratory tract-how to treat? Or do not treat?

BACKGROUND

Acute and chronic respiratory tract infections are a common cause of inappropriate antimicrobial prescription. Antimicrobial therapy leads to the development of resistance and the emergence of opportunistic pathogens that substitute the indigenous microbiota.

METHODS

This review explores the major challenges and lines of research to adequately establish the clinical role of bacteria and the indications for antimicrobial treatment, and reviews novel therapeutic approaches.

RESULTS

In patients with chronic pulmonary diseases and structural disturbances of the bronchial tree or the lung parenchyma, clinical and radiographic signs and symptoms are almost constantly present, including a basal inflammatory response. Bacterial adaptative changes and differential phenotypes are described, depending on the clinical role and niche occupied. The respiratory tract has areas that are potentially inaccessible to antimicrobials. Novel therapeutic approaches include new ways of administering antimicrobials that may allow intracellular delivery or delivery across biofilms, targeting the functions essential for infection, such as regulatory systems, or the virulence factors required to cause host damage and disease. Alternatives to antibiotics and antimicrobial adjuvants are under development.

CONCLUSIONS

Prudent treatment, novel targets, and improved drug delivery systems will contribute to reduce the emergence of antimicrobial resistance in lower respiratory tract infections.

Procalcitonin for selecting the antibiotic regimen in outpatients with low-risk community-acquired pneumonia using a rapid point-of-care testing: A single-arm clinical trial

OBJECTIVE

We aimed to assess the role of procalcitonin (PCT) to guide the initial selection of the antibiotic regimen for low-risk community-acquired pneumonia (CAP).

METHODS

A single-arm clinical trial was conducted including outpatients with CAP and Pneumonia Severity Index risk classes I-II. Antimicrobial selection was based on the results of PCT measured with a rapid point-of-care testing. According to serum PCT levels, patients were assigned to two treatment strategies: oral azithromycin if PCT was <0.5 ng/ml, or levofloxacin if levels were ≥0.5 ng/ml. Primary outcome was clinical cure rate. Short-term and long-term outcomes were assessed. Results were compared with those of a historical standard-of-care control-group treated in our centre.

RESULTS

Of 253 subjects included, 216 (85.4%) were assigned to azithromycin. Pneumococcal infection was diagnosed in 26 (12%) and 21 (56.8%) patients allocated to azithromycin and levofloxacin groups, respectively. No patients in the azithromycin group developed bacteraemia. Atypical organisms were more common in patients given azithromycin (18.5% vs 8.1%, respectively). The majority (93%) of patients with atypical pneumonia had low PCT levels. Clinical cure rates were 95.8% in the azithromycin group, 94.6% in the levofloxacin group, and 94.4% in the historical control group. No 30-day mortality or recurrences were observed, and the 3-year rates of recurrence and mortality were very low in both groups. Adverse events occurrence was also infrequent.

CONCLUSION

A PCT-guided strategy with a rapid point-of-care testing safely allowed selecting empirical narrow-spectrum antibiotics in outpatients with CAP.

TRIAL REGISTRATION

The study is registered with ClinicalTrials.gov, number NCT02600806.

Prevalence of Atypical Pathogens in Patients With Cough and Community-Acquired Pneumonia: A Meta-Analysis

PURPOSE

Community-acquired pneumonia (CAP), acute cough, bronchitis, and lower respiratory tract infections (LRTI) are often caused by infections with viruses or Streptococcus pneumoniae. The prevalence of atypical pathogens Mycoplasma pneumoniae, Chlamydophila pneumoniae, Legionella pneumophila, and Bordetella pertussis among patients with these illnesses in the ambulatory setting has not been previously summarized. We set out to derive prevalence information from the existing literature.

METHODS

We performed a systematic review of MEDLINE for prospective, consecutive-series studies reporting the prevalence of M pneumoniae, C pneumoniae, L pneumophila and/or B pertussis in outpatients with cough, acute bronchitis, LRTI, or CAP. Articles were independently reviewed by 2 authors for inclusion and abstraction of data; discrepancies were resolved by consensus discussion. A meta-analysis was performed on each pathogen to calculate the pooled prevalence estimates using a random effects model of raw proportions.

RESULTS

Fifty studies met our inclusion criteria. While calculated heterogeneity was high, most studies reported prevalence for each pathogen within a fairly narrow range. In patients with CAP, the overall prevalences of M pneumoniae and C pneumoniae were 10.1% (95% CI, 7.1%-13.1%) and 3.5% (95% CI, 2.2%-4.9%), respectively. Consistent with previous reports, M pneumoniae prevalence peaked in roughly 6-year intervals. Overall prevalence of L pneumophila was 2.7% (95% CI, 2.0%-3.4%), but the organism was rare in children, with only 1 case in 1,765. In patients with prolonged cough in primary care, the prevalence of B pertussis was 12.4% (95% CI, 4.9%-19.8%), although it was higher in studies that included only children (17.6%; 95% CI, 3.4%-31.8%).

CONCLUSIONS

Atypical bacterial pathogens are relatively common causes of lower respiratory diseases, including cough, bronchitis, and CAP. Where surveillance data were available, we found higher prevalences in studies where all patients are tested for these pathogens. It is likely that these conditions are underreported, underdiagnosed, and undertreated in current clinical practice.

Procalcitonin as a Diagnostic and Prognostic Factor for Tuberculosis Meningitis

Background and Purpose

We investigated the potential role of serum procalcitonin in differentiating tuberculosis meningitis from bacterial and viral meningitis, and in predicting the prognosis of tuberculosis meningitis.

Methods

This was a retrospective study of 26 patients with tuberculosis meningitis. In addition, 70 patients with bacterial meningitis and 49 patients with viral meningitis were included as the disease control groups for comparison. The serum procalcitonin level was measured in all patients at admission. Differences in demographic and laboratory data, including the procalcitonin level, were analyzed among the three groups. In addition, we analyzed the predictive factors for a prognosis of tuberculosis meningitis using the Glasgow Coma Scale (GCS) at discharge, and the correlation between the level of procalcitonin and the GCS score at discharge.

Results

Multiple logistic regression analysis showed that a low level of procalcitonin (≤1.27 ng/mL) independently distinguished tuberculosis meningitis from bacterial meningitis. The sensitivity and specificity for distinguishing tuberculosis meningitis from bacterial meningitis were 96.2% and 62.9%, respectively. However, the level of procalcitonin in patients with tuberculosis meningitis did not differ significantly from that in patients with viral meningitis. In patients with tuberculosis meningitis, a high level of procalcitonin (>0.4 ng/mL) was a predictor of a poor prognosis, and the level of procalcitonin was negatively correlated with the GCS score at discharge (r=-0.437, p=0.026).

Conclusions

We found that serum procalcitonin is a useful marker for differentiating tuberculosis meningitis from bacterial meningitis and is also valuable for predicting the prognosis of tuberculosis meningitis.

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.

Can we predict pneumococcal bacteremia in patients with severe community-acquired pneumonia?

PURPOSE

This study aimed to evaluate the role of biomarkers as markers of pneumococcal bacteremia in severe community-acquired pneumonia (SCAP).

MATERIALS AND METHODS

A prospective, single-center, observational cohort study of 108 patients with SCAP admitted to the intensive care department of a university hospital in Portugal was conducted. Leucocytes, C-reactive protein (CRP), lactate, procalcitonin (PCT), d-dimer, brain natriuretic peptide (BNP), and cortisol were measured within 12 hours after the first antibiotic dose.

RESULTS

Fifteen patients (14%) had bacteremic pneumococcal pneumonia (BPP). They had significantly higher levels of median CRP (301 [interquartile range, or IQR], 230-350] mg/L vs 201 [IQR, 103-299] mg/L; P = .023), PCT (40 [IQR, 25-102] ng/mL vs 8 [IQR, 2-26] ng/mL; P < .001), BNP (568 [IQR, 478-2841] pg/mL vs 407 [IQR, 175-989] pg/mL; P = .027), and lactate (5.5 [IQR, 4.5-9.8] mmol/L vs 3.1 [IQR, 1.9-6.2] mmol/L; P = .009) than did patients without BPP. The discriminatory power evaluated by the area under the receiver operating characteristic curve (aROC) for PCT (aROC, 0.79) was superior to lactate (aROC, 0.71), BNP (aROC, 0.67), and CRP (aROC, 0.70). At a cutoff point of 17 ng/mL, PCT showed a sensitivity of 87%, a specificity of 67%, a positive predictive value of 30% and a negative predictive value of 97%, as a marker of pneumococcal bacteremia.

CONCLUSIONS

In this cohort, significantly higher PCT, BNP, lactate, and CRP levels were found in BPP, and PCT presented the best ability to identify pneumococcal bacteremia. A PCT serum level lower than 17 ng/mL could identify patients with SCAP unlikely to have pneumococcal bacteremia.

High serum levels of procalcitonin and soluble TREM-1 correlated with poor prognosis in pulmonary tuberculosis

OBJECTIVES

Comparisons of procalcitonin (PCT), C-reactive protein (CRP), and soluble triggering receptor expressed on myeloid cells-1 (sTREM-1) would expand our knowledge of which biomarker is the best predictor for outcomes of patients with pulmonary tuberculosis (PTB).

METHODS

We prospectively enrolled 243 PTB patients, in whom PCT, CRP, and sTREM-1 measurement were performed to evaluate their prognostic value for 6-month mortality.

RESULTS

Serum PCT, CRP, and sTREM-1 levels on diagnosis of PTB were significantly higher in nonsurvivors (2.22 ± 6.22 vs. 0.13 ± 0.31 ng/mL, P = 0.043; 42.1 ± 59.4 vs. 12.5 ± 29.1 mg/L, P = 0.004; 332 ± 362 vs. 128 ± 98 pg/mL, P = 0.001, respectively) as compared with 6-month survivors. In multivariate Cox regression analysis, PCT ≧ 0.5 ng/mL (hazard ratio 4.13, 95% CI, 1.99-8.58) and sTREM-1 ≧ 129 pg/mL (hazard ratio 3.39, 95% CI, 1.52-7.58) remained independent mortality predictors. Serum PCT and sTREM-1 levels above the cutoffs were also associated with the presence of disseminated tuberculosis.

CONCLUSIONS

Among PTB patients, higher PCT, CRP, and sTREM-1 levels are observed in nonsurvivors than in 6-month survivors. Serum levels of PCT and sTREM-1 over the cutoffs are independently associated with a poor outcome. In addition, higher PCT and sTREM-1 levels would raise the clinical suspicion of disseminated tuberculosis.

[Diagnostic and prognostic power of biomarkers to improve the management of community acquired pneumonia in the emergency department]

OBJECTIVES

To analyse the usefulness and performance of several biomarkers [C-reactive protein (CRP), mid-regional pro-adrenomedullin (MR-proADM), procalcitonin (PCT)] and lactate in predicting short- and medium-term mortality compared with the prognostic severity scales (PSS) usually employed for community-acquired pneumonia (CAP) and in assessing the aetiological suspicion of infection by Streptococcus pneumoniae and bacteraemia.

METHODS

Observational, prospective and analytical study was conducted on patients who were diagnosed with CAP in our emergency department (ED). The data collected included socio-demographic and comorbidity variables, Charlson index, priority level according to the Spanish Triage System (STS), stage in the Pneumonia Severity Index (PSI) and in the CURB-65 (confusion, urea, respiratory rate, blood pressure and age ≥65years), criteria of severe CAP, microbiological studies, and biomarkers determinations. The patients were followed-up for 180days to calculate the prognostic power and the diagnostic performance for bacteraemia and aetiology.

RESULTS

A total of 127patients were finally enrolled in the study. The 30-day mortality was 10.3% (13), and 22.6% (28) at 180 days. Blood cultures were positive in 29 patients (23%) and S.pneumoniae was identified as the responsible pathogen in 28 cases (22.2%). The area under the ROC curve (AUC-ROC) for lactate and MR-proADM to predict 30-day mortality was 0.898 (95%CI: 0.824-0.973; P<.0001) and 0.892 (95%CI: 0.811-0.974; P<.0001), respectively, and for MR-proADM at 180 days it was 0.921 (95%CI: 0.874-0.968; P<.0001). The AUC-ROC for PCT to predict bacteraemia was 0.952 (95%CI: 0.898-1.000; P<.0001) and, considering a cut-off value ≥0.95ng/ml, the negative predictive value (NPV) and the likelihood ratio (LR+) were 97.8% and 9.03, respectively. Using a PCT cut-off value >0.85ng/ml, the NPV and the LR+ were 96.6% and 5.89%, respectively, to predict a S.pneumoniae infection.

CONCLUSIONS

MR-proADM and lactate showed a similar or even better performance for 30-day intra-hospital mortality than PSI, CURB-65, STS and CAP severity criteria in patients diagnosed with CAP (P>.05). Furthermore, the MR-proADM capacity to predict 180-day mortality was higher than PSS and the rest of biomarkers (P>.05), and its AUC-ROC increased if it was used in combination with PSI, CURB65 and STS. The determination of PCT has a remarkable diagnostic performance to rule out bacteraemia and to orientate the aetiology towards a S.pneumoniae infection.

Correlation of inflammatory and cardiovascular biomarkers with pneumonia severity scores

PURPOSE

To assess the correlation of procalcitonin (PCT), C-reactive protein (CRP), neopterin, mid-regional pro-atrial natriuretic peptide (MR-proANP), and mid-regional pro-adrenomedullin (MR-proADM) with severity risk scores: severe CAP (SCAP) and SMART-COP in patients with community-acquired pneumonia (CAP), as well as short term prognosis and to determine the correlation with mortality risk scores.

METHODS

Eighty-five patients with a final diagnosis of pneumonia were consecutively included during a two month period. Epidemiological, clinical, microbiological, and radiological data were recorded. Patients were stratified according to the PSI, CURB-65, SCAP and SMART-COP. Complications were defined as respiratory failure/shock, need of ICU, and death. Plasma samples were collected at admission.

RESULTS

MR-proANP and MR-proADM showed significantly higher levels in high risk SCAP group in comparison to low risk. When considering SMART-COP none of the biomarkers showed statistical differences. MR-proADM levels were high in patients with high risk of needing intensive respiratory or vasopressor support according to SMRT-CO. Neopterin and MR-proADM were significantly higher in patients that developed complications. PCT and MR-proADM showed significantly higher levels in cases of a definite bacterial diagnosis in comparison to probable bacterial, and unknown origin. MR-proANP and MR-proADM levels increased statistically according to PSI and CURB-65.

CONCLUSIONS

Biomarker levels are higher in pneumonia patients with a poorer prognosis according to SCAP and SMART-COP indexes, and to the development of complications.

Serum levels of neopterin during antimicrobial treatment for Mycobacterium ulcerans infection

Neopterin is closely associated with activation of the cellular immune system. Neopterin levels differed between controls and patients with Buruli ulcer disease. No differences between patients with or without paradoxical responses were observed. Therefore, neopterin has no value in detecting paradoxical responses among patients with limited Buruli ulcer disease. Neopterin levels were lower in patients receiving clarithromycin. This finding might indicate a slower cellular immune recovery, with possible consequences in future therapy with clarithromycin.

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.

Surrogate markers of infection: interrogation of the immune system

Infectious diseases remain the greatest causes of morbidity and mortality in global terms. As much of the burden occurs in the developing world, limited access to diagnostic testing has hampered the diagnosis and treatment of these conditions, while, in the developed world, the cost of managing infectious diseases remains considerable. Despite the size of the problem there remains an ongoing need for tests that improve diagnostic sensitivity and specificity, provide more rapid diagnoses, are available for point-of-care testing in remote regions, and can help inform therapeutic decision-making by identifying resistance patterns or patient outcomes. This article discusses the background to biomarker development for infectious diseases, some current assays that are providing useful information regarding the host's response to infection (using examples such as Cytomegalovirus and Mycobacterium tuberculosis), as well as likely future technologies and their limitations.

Usefulness of consecutive biomarkers measurement in the management of community-acquired pneumonia

The aim of this study was to investigate whether procalcitonin (PCT), neopterin, C-reactive protein (CRP), and mid regional pro-atrial natriuretic peptide (MR-proANP) levels at admission and during the clinical course can be useful for the management of patients with pneumonia. The study population consisted of 75 patients with clinical and radiological diagnosis of pneumonia. Serum samples were collected at admission and during hospitalization. Complications were defined as intensive care unit (ICU) admission or death. The levels of PCT were significantly higher in pneumonia of definite bacterial origin in comparison to probable bacterial or unknown origin. The PCT levels were higher in pneumococcal pneumonia. The PCT and MR-proANP levels increased significantly according to the Pneumonia Severity Index (PSI). All biomarkers levels are higher in patients developing complications and who were dying. The serial levels of MR-proANP remain significantly elevated in patients developing complications and in patients classified in PSI and CURB-65 risk groups. In patients not developing complications, there is a significant decrease in the PCT levels. PCT can be useful for identifying pneumonia etiology. PCT and MR-proANP levels correlate with pneumonia severity rules. PCT and MR-proANP serial measurements can be useful for predicting short-term prognosis. Systemic biomarkers can provide additional information regarding clinical evolution, because these are dynamic and can be measured daily.

Value of procalcitonin, C-reactive protein, and neopterin in exacerbations of chronic obstructive pulmonary disease

Objective:

The identification of biological markers in order to assess different aspects of COPD is an area of growing interest. The objective of this study was to investigate whether levels of procalcitonin (PCT), C-reactive protein (CRP), and neopterin in COPD patients could be useful in identifying the etiological origin of the exacerbation and assessing its prognosis.

Methods:

We included 318 consecutive COPD patients: 46 in a stable phase, 217 undergoing an exacerbation, and 55 with pneumonia. A serum sample was collected from each patient at the time of being included in the study. A second sample was also collected 1 month later from 23 patients in the exacerbation group. We compared the characteristics, biomarker levels, microbiological findings, and prognosis in each patient group. PCT and CRP were measured using an immunofluorescence assay. Neopterin levels were measured using a competitive immunoassay.

Results:

PCT and CRP showed significant differences among the three patient groups, being higher in patients with pneumonia, followed by patients with exacerbation (P < 0.0001). For the 23 patients with paired samples, PCT and CRP levels decreased 1 month after the exacerbation episode, while neopterin increased. Neopterin showed significantly lower levels in exacerbations with isolation of pathogenic bacteria, but no differences were found for PCT and CRP. No significant differences were found when comparing biomarker levels according to the Gram result: PCT (P = 0.191), CRP (P = 0.080), and neopterin (P = 0.109). However, median values of PCT and CRP were high for Streptococcus pneumoniae, Staphylococcus aureus, and enterobacteria. All biomarkers were higher in patients who died within 1 month after the sample collection than in patients who died later on.

Conclusions:

According to our results, biomarker levels vary depending on the clinical status. However, the identification of the etiology of infectious exacerbation by means of circulating biomarkers is encouraging, but its main disadvantage is the absence of a microbiological gold standard, to definitively demonstrate their value. High biomarker levels during an exacerbation episode correlate with the short-term prognosis, and therefore their measurement can be useful for COPD management.

Elevated procalcitonin predicts Gram-negative sepsis in haematological patients with febrile neutropenia

OBJECTIVE

To compare semi-quantitative procalcitonin with C-reactive protein in predicting bacteraemia in haematological patients with neutropenic fever.

METHODS

A total of 77 patients treated with intensive chemotherapy for haematological malignancy at Kuopio University Hospital were candidates for study entry. Eleven of these patients did not fulfil the criteria for neutropenic fever, and 66 patients were finally included. Nineteen patients had acute myeloid leukaemia and 47 had received high-dose chemotherapy supported by autologous stem cell transplant. Ninety neutropenic fever episodes in these 66 patients fulfilled the study entry criteria, with microbiological cultures, procalcitonin and C-reactive protein measurements available. Serum procalcitonin and C-reactive protein were analyzed at the onset of each neutropenic fever episode on day 0, and then daily from days 1 to 4.

RESULTS

Bacteraemia was observed in 21 episodes (23%) and the criteria for severe sepsis were fulfilled in 13 episodes (14%). Half of the bacteraemic episodes were caused by Gram-negative bacteria. The kinetics of procalcitonin and C-reactive protein were similar, with increasing levels for 2 to 4 days after the onset of fever. The procalcitonin level on days 1, 2, 3 and 4 was associated with bacteraemia and Gram-negative bacteraemia, but not with the development of severe sepsis. On day 1, a procalcitonin level above 0.5 ng/ml had a sensitivity of 57% and 70% and specificity of 81% and 77% to predict bacteraemia and Gram-negative bacteraemia, respectively.

CONCLUSIONS

An elevated level of procalcitonin within 24 h after the onset of neutropenic fever predicts bacteraemia and Gram-negative bacteraemia in haematological patients.

Usefulness of mid regional pro-atrial natriuretic peptide in the exacerbations of chronic obstructive pulmonary disease

BACKGROUND

A recent approach for the management of chronic obstructive pulmonary disease (COPD) is the measurement of systemic biomarkers. The aim of this study was to evaluate the usefulness of mid regional pro-atrial natriuretic peptide (MR-proANP) to predict short and long term prognosis.

METHODS

We included 318 COPD patients: 46 in a stable phase, 217 undergoing an exacerbation and 55 with pneumonia. Serum samples were collected at admission. For 20 exacerbated patients, we also collected a second sample one month later. MR-proANP was measured by an inmunofluorescent assay.

RESULTS

Statistically higher levels of MR-proANP were found in patients with pneumonia when comparing to patients in the stable state (p=0.031). For those patients with paired samples, MR-proANP decreased statistically one month later (p=0.027). MR-proANP showed significant lower levels in exacerbations with isolation of pathogenic bacteria (p=0.011). MR-proANP levels were higher in patients that died within one month, decreasing as long as the moment of death occurred later on (p=0.163).

CONCLUSIONS

The identification of exacerbation etiology by means of MR-proANP is not clinically reliable. Levels of MR-proANP vary depending on the clinical status, being higher during pneumonia in comparison to the stable state. MR-proANP levels were higher in patients that died within one month after the exacerbation episode.

Biomarkers and diagnostics for tuberculosis: progress, needs, and translation into practice

Human infection with Mycobacterium tuberculosis can progress to active disease, be contained as latent infection, or be eradicated by the host response. Tuberculosis diagnostics classify a patient into one of these categories. These are not fixed distinct states, but rather are continua along which patients can move, and are affected by HIV infection, immunosuppressive therapies, antituberculosis treatments, and other poorly understood factors. Tuberculosis biomarkers-host or pathogen-specific-provide prognostic information, either for individual patients or study cohorts, about these outcomes. Tuberculosis case detection remains difficult, partly because of inaccurate diagnostic methods. Investments have yielded some progress in development of new diagnostics, although the existing pipeline is limited for tests for sputum-smear-negative cases, childhood tuberculosis, and accurate prediction of reactivation of latent tuberculosis. Despite new, sensitive, automated molecular platforms for detection of tuberculosis and drug resistance, a simple, inexpensive point-of-care test is still not available. The effect of any new tests will depend on the method and extent of their introduction, the strength of the laboratories, and the degree to which access to appropriate therapy follows access to diagnosis. Translation of scientific progress in biomarkers and diagnostics into clinical and public health programmes is possible-with political commitment, increased funding, and engagement of all stakeholders.

Prognostic value of procalcitonin in Legionella pneumonia

The diagnostic reliability and prognostic implications of procalcitonin (PCT) (ng/ml) on admission in patients with community-acquired pneumonia (CAP) due to Legionella pneumophila are unknown. We retrospectively analysed PCT values in 29 patients with microbiologically proven Legionella-CAP admitted to the University Hospital Basel, Switzerland, between 2002 and 2007 and compared them to other markers of infection, namely, C-reactive protein (CRP) (mg/l) and leukocyte count (10(9)/l), and two prognostic severity assessment scores (PSI and CURB65). Laboratory analysis demonstrated that PCT values on admission were >0.1 in over 93%, >0.25 in over 86%, and >0.5 in over 82% of patients with Legionella-CAP. Patients with adverse medical outcomes (59%, n = 17) including need for ICU admission (55%, n = 16) and/or inhospital mortality (14%, n = 4) had significantly higher median PCT values on admission (4.27 [IQR 2.46-9.48] vs 0.97 [IQR 0.29-2.44], p = 0.01), while the PSI (124 [IQR 81-147] vs 94 [IQR 75-116], p = 0.19), the CURB65 (2 [IQR 1-2] vs 1 [1-3], p = 0.47), CRP values (282 [IQR 218-343], p = 0.28 vs 201 [IQR 147-279], p = 0.28), and leukocyte counts (12 [IQR 10-21] vs 12 [IQR 9-15], p = 0.58) were similar. In receiver operating curves, PCT concentrations on admission had a higher prognostic accuracy to predict adverse outcomes (AUC 0.78 [95%CI 0.61-96]) as compared to the PSI (0.64 [95%CI 0.43-0.86], p = 0.23), the CURB65 (0.58 [95%CI 0.36-0.79], p = 0.21), CRP (0.61 [95%CI 0.39-0.84], p = 0.19), and leukocyte count (0.57 [95%CI 0.35-0.78], p = 0.12). Kaplan-Meier curves demonstrated that patients with initial PCT values above the optimal cut-off of 1.5 had a significantly higher risk of death and/or ICU admission (log rank p = 0.003) during the hospital stay. In patients with CAP due to Legionella, PCT levels on admission might be an interesting predictor for adverse medical outcomes.

Procalcitonin assay in systemic inflammation, infection, and sepsis: clinical utility and limitations

OBJECTIVE

The use of procalcitonin (ProCT) as a marker of several clinical conditions, in particular, systemic inflammation, infection, and sepsis, will be clarified, and its current limitations will be delineated. In particular, the need for a more sensitive assay will be emphasized. For these purposes, the medical literature comprising clinical studies pertaining to the measurement of serum ProCT in various clinical settings was examined.

DATA SOURCE AND SELECTION

A PubMed search (1965 through November 2007) was conducted, including manual cross-referencing. Pertinent complete publications were obtained using the MeSH terms procalcitonin, C-reactive protein, sepsis, and biological markers. Textbook chapters were also read and extracted.

DATA EXTRACTION AND SYNTHESIS

Available clinical and other patient data from these sources were reviewed, including any data relating to precipitating factors, clinical findings, associated illnesses, and patient outcome. Published data concerning sensitivity, specificity, and reproducibility of ProCT assays were reviewed.

CONCLUSIONS

Based on available data, the measurement of serum ProCT has definite utility as a marker of severe systemic inflammation, infection, and sepsis. However, publications concerning its diagnostic and prognostic utility are contradictory. In addition, patient characteristics and clinical settings vary markedly, and the data have been difficult to interpret and often extrapolated inappropriately to clinical usage. Furthermore, attempts at meta-analyses are greatly compromised by the divergent circumstances of reported studies and by the sparsity and different timing of the ProCT assays. Although a high ProCT commonly occurs in infection, it is also elevated in some noninfectious conditions. Thus, the test is not a specific indicator of either infection or sepsis. Moreover, in any individual patient, the precipitating cause of an illness, the clinical milieu, and complicating conditions may render tenuous any reliable estimations of severity or prognosis. It also is apparent that even a febrile septic patient with documented bacteremia may not necessarily have a serum ProCT that is elevated above the limit of functional sensitivity of the assay. In this regard, the most commonly applied assay (i.e., LUMItest) is insufficiently sensitive to detect potentially important mild elevations or trends. Clinical studies with a more sensitive ProCT assay that is capable of rapid and practicable day-to-day monitoring are needed and shortly may be available. In addition, investigations showing that ProCT and its related peptides may have mediator relevance point to the need for evaluating therapeutic countermeasures and studying the pathophysiologic effect of hyperprocalcitonemia in serious infection and sepsis.

Useulness of B Natriuretic Peptides and Procalcitonin in Emergency Medicine

Congestive heart failure (CHF) is the main cause of acute dyspnea in patients presented to an emergency department (ED), and it is associated with high morbidity and mortality. B-type natriuretic peptide (BNP) is a polypeptide, released by ventricular myocytes directly proportional to wall tension, for lowering renin-angiotensin-aldosterone activation. For diagnosing CHF, both BNP and the biologically inactive NT-proBNP have similar accuracy. Threshold values are higher in elderly population, and in patients with renal dysfunction. They might have also a prognostic value. Studies demonstrated that the use of BNP or NT-proBNP in dyspneic patients early in the ED reduced the time to discharge, total treatment cost. BNP and NT-proBNP should be available in every ED 24 hours a day, because literature strongly suggests the beneficial impact of an early appropriate diagnosis and treatment in dyspneic patients.

Etiologic diagnosis of febrile patients who present to an ED is complex and sometimes difficult. However, new evidence showed that there are interventions (including early appropriate antibiotics), which could reduce mortality rate in patients with sepsis. For diagnosing sepsis, procalcitonin (PCT) is more accurate than C-reactive protein. Thus, because of its excellent specificity and positive predictive value, an elevated PCT concentration (higher than 0.5 ng/mL) indicates ongoing and potentially severe systemic infection, which needs early antibiotics (e.g. meningitis). In lower respiratory tract infections, CAP or COPD exacerbation, PCT guidance reduced total antibiotic exposure and/or antibiotic treatment duration.

Serum procalcitonin elevation in critically ill patients at the onset of bacteremia caused by either Gram negative or Gram positive bacteria

Background

In the ICU, bacteremia is a life-threatening infection whose prognosis is highly dependent on early recognition and treatment with appropriate antibiotics. Procalcitonin levels have been shown to distinguish between bacteremia and noninfectious inflammatory states accurately and quickly in critically ill patients. However, we still do not know to what extent the magnitude of PCT elevation at the onset of bacteremia varies according to the Gram stain result.

Methods

Review of the medical records of every patient treated between May, 2004 and December, 2006 who had bacteremia caused by either Gram positive (GP) or Gram negative (GN) bacteria, and whose PCT dosage at the onset of infection was available.

Results

97 episodes of either GN bacteremia (n = 52) or GP bacteremia (n = 45) were included. Procalcitonin levels were found to be markedly higher in patients with GN bacteremia than in those with GP bacteremia, whereas the SOFA score value in the two groups was similar. Moreover, in the study population, a high PCT value was found to be independently associated with GN bacteremia. A PCT level of 16.0 ng/mL yielded an 83.0% positive predictive value and a 74.0% negative predictive value for GN-related bacteremia in the study cohort (AUROCC = 0.79; 95% CI, 0.71–0.88).

Conclusion

In a critically ill patient with clinical sepsis, GN bacteremia could be associated with higher PCT values than those found in GP bacteremia, regardless of the severity of the disease.

Endothelin-1 precursor peptides correlate with severity of disease and outcome in patients with community acquired pneumonia

Background

Circulating levels of endothelin-1 are increased in sepsis and correlate with severity of disease. A rapid and easy immunoassay has been developed to measure the more stable ET-1 precursor peptides proET-1. The objective of this study was to assess the diagnostic and prognostic value of proET-1 in a prospective cohort of mainly septic patients with community-acquired pneumonia.

Methods

We evaluated 281 consecutive patients with community acquired pneumonia. Serum proET-1 plasma levels were measured using a new sandwich immunoassay.

Results

ProET-1 levels exhibited a gradual increase depending on the clinical severity of pneumonia as assessed by the pneumonia severity index (PSI) and the CURB65 scores (p < 0.001 and p < 0.01). The diagnostic accuracy to predict bacteraemia of procalcitonin (AUC 0.84 [95% 0.74–0.93]) was superior than C-reactive protein (AUC 0.67 [95%CI 0.56–0.78]) and leukocyte count (AUC 0.66 [95%CI 0.55–0.78]) and in the range of proET-1(AUC of 0.77 [95%CI 0.67–0.86]). ProET-1 levels on admission were increased in patients with adverse medical outcomes including death and need for ICU admission. ROC curve analysis to predict the risk for mortality showed a prognostic accuracy of proET-1 (AUC 0.64 [95%CI 0.53–0.74]), which was higher than C-reactive protein (AUC 0.51 [95%CI 0.41–0.61]) and leukocyte count (AUC 0.55 [95%CI 0.44–0.65]) and within the range of the clinical severity scores (PSI AUC 0.69 [95%CI 0.61–0.76] and CURB65 0.67 [95%CI 0.57–0.77]) and procalcitonin (AUC 0.59 [95% 0.51–0.67]). ProET-1 determination improved significantly the prognostic accuracy of the CURB65 score (AUC of the combined model 0.69 [95%CI 0.59–0.79]). In a multivariate logistic regression model, only proET1 and the clinical severity scores were independent predictors for death and for the need for ICU admission.

Conclusion

In community-acquired pneumonia, ET-1 precursor peptides correlate with disease severity and are independent predictors for mortality and ICU admission. If confirmed in future studies, proET-1 levels may become another helpful tool for risk stratification and management of patients with community-acquired pneumonia.

Trial registration

ISRCTN04176397

Midregional pro-atrial natriuretic peptide as a prognostic marker in pneumonia

OBJECTIVE

To evaluate the usefulness of midregional pro-atrial natriuretic peptide (MR-proANP) measurement in the stratification of severity in community-acquired pneumonia.

METHODS

The population studied was three hundred patients admitted to Emergency Department of a tertiary university hospital presenting clinical signs of lower respiratory tract infection, a new infiltrate on the chest radiograph and a confirmed pneumonia by clinical evolution. Patients were stratified by the Pneumonia Severity Index (PSI), by CURB-65 score and by the development of complications. Serum samples were obtained at the moment of admission and prior to antibiotic therapy, and stored until analysis. MR-proANP was measured by B.R.A.H.M.S MR-proANP KRYPTOR.

RESULTS

Serum levels of MR-proANP increased with the severity of pneumonia, according to PSI score and CURB-65 score. Median MR-proANP levels were significantly higher (p<0.0001) in patients with high PSI risk class (IV-V) than in those with low PSI risk class (I-III). MR-proANP levels were also significantly higher (p=0.029) in those patients that developed complications or died. There was no association between MR-proANP and etiology of pneumonia and the radiographic extent.

CONCLUSION

We can conclude that MR-proANP measurement was helpful for individual risk assessment in patients with pneumonia admitted to the emergency department.

Circulating levels of copeptin, a novel biomarker, in lower respiratory tract infections

BACKGROUND

Vasopressin has haemodynamic as well as osmoregulatory effects, and reflects the individual stress response. Copeptin is co-synthesized with vasopressin, directly mirroring vasopressin levels, but is more stable in plasma and serum. Both levels are increased in patients with septic shock. Lower respiratory tract infections (LRTI) are a precursor of sepsis. Thus, we investigated circulating levels and the prognostic use of copeptin for the severity and outcome in patients with LRTI.

MATERIALS AND METHODS

Five hundred and forty-five consecutive patients with LRTI and 50 healthy controls were evaluated. Serum copeptin levels were measured with a new chemiluminescent sandwich immunoassay.

RESULTS

Of the 545 patients, 373 had community-acquired pneumonia (CAP), 60 acute exacerbations of chronic obstructive pulmonary disease (COPD), 59 acute bronchitis, 13 exacerbations of asthma and 40 other final diagnoses. Copeptin levels were significantly higher in patients with LRTI as compared to controls (P < 0.001) with highest levels in patients with CAP. Copeptin levels increased with increasing severity of CAP, as classified by the pneumonia severity index (PSI) (P < 0.001). In patients who died, copeptin levels on admission were significantly higher as compared to levels in survivors [70.0 (28.8-149.0) vs. 24.3 (10.8-43.8) pmol L(-1), P < 0.001]. The area under the receiver operating curve (AUC) for survival was 0.75 for copeptin, which was significantly higher as compared to C-reactive protein (AUC 0.61, P = 0.01), leukocyte count (AUC 0.59, P = 0.01) and similar to procalcitonin (AUC 0.68, P = 0.21).

CONCLUSIONS

Copeptin levels are increased with increasing severity of LRTI namely in patients with CAP and unfavourable outcome. Copeptin levels, as a novel biomarker, might be a useful tool in the risk stratification of patients with LRTI.

Legionnaires’ Disease

The incidence of legionnaires’ disease (LD) seems to increase with age, particularly in males [36]. It was considered an infrequent cause of pneumonia in the past, but it currently ranks second to pneumococcus in the list of etiologic agents of severe community-acquired pneumonia (CAP) of bacterial origin [2, 24, 60, 89]. Considering less severe cases, in a series of 145 pneumonias in which BCYE culture, serology and the Legionella urinary antigen (LUA) test were systematically applied, Vergis et al. [91] reported a prevalence of LD of 13.7%. In another series of 392 adult patients with CAP treated in a university hospital, Sopena et al. found a prevalence of 12.5%, and LD was the second cause of pneumonia [83].