Procalcitonin and pneumonia: is it a useful marker?

Can Procalcitonin Be Dosed in Bovine Milk Using a Commercial ELISA Kit?

Simple Summary

Mastitis is one of the major economic and animal welfare problems on dairy farms. The gold standard test for mastitis diagnosis is milk culture, but bacteria are not always isolated (only in 11–44% of milk samples from clinical cases of mastitis) and sometimes a positive culture can result from a contamination of the milk. Procalcitonin is a new biomarker which may lead to an early detection of inflammation due to bacterial infection. In humans, procalcitonin concentration has also been evaluated in milk in addition to plasma. The authors aimed to evaluate the possible application of a commercially available ELISA kit for bovine procalcitonin for the assessing of procalcitonin in bovine milk samples. Plasma and milk samples from cows with mastitis were collected to measure procalcitonin concentrations by using a bovine procalcitonin ELISA kit. Our results showed that the ELISA kit tested can be employed to assess bovine procalcitonin in plasma but not for analyzing milk samples.

Abstract

The aim was to evaluate the use of a bovine procalcitonin (PCT) ELISA kit (Cusabio, China) for assessing PCT in bovine milk samples. Validation was performed by using 10 plasma and corresponding milk samples from mastitic cows. The limit of detection (LOD) was calculated. The coefficient of variation (CV%) of the readings of five plasma samples measured five times in the same plate (intra-assay) and the CV% of the same five samples read five times in three separate plates was evaluated. Parallelism was determined by serial twofold dilutions of five plasma and corresponding milk samples. Milk samples were analyzed with and without centrifugation. Regarding plasma PCT, the method presented an inter- and intra-CV < 23.7% and parallelism had very good recovery values. The ELISA kit studied can measure bovine plasma PCT concentrations. The kit antibodies fail in binding PCT in milk samples because all centrifuged milk samples showed a lower LOD than blank samples. Only three uncentrifuged milk samples showed measurable PCT concentrations. Due to these results, the commercial ELISA kit investigated could not be employed for the detection of PCT in milk samples.

Community-Acquired Pneumonia: A Focused Review

Community-acquired pneumonia (CAP) is a common cause for admission to the hospital and contributes significantly to patient morbidity and healthcare cost. We present a review of the epidemiology, pathophysiology, risk factors, symptoms, diagnosis, presentations, risk-stratification, markers, and management of CAP in the United States (US). The overall incidence of CAP is 16 to 23 cases per 1000 persons per year, and the rate increases with age. Some of the risk factors for CAP include comorbidities such as, chronic obstructive pulmonary disease (COPD), asthma, and heart failure. CAP symptoms vary, and typically include productive cough, dyspnea, pleuritic pain, abnormal vital signs (e.g., fever, tachycardia), and abnormal lung examination findings. A diagnosis can be made by radiography, which has the additional benefit of helping to identify patterns associated with typical and atypical CAP. There are risk-stratification calculators that can be used routinely by physicians to triage patients, and to determine adequate management. The Infectious Diseases Society of America (IDSA) and the American Thoracic Society (ATS) developed the Pneumonia Severity Index (PSI) which incorporates 20 risk factors to place patients into 5 classes correlated with mortality risk. In addition, the British Thoracic Society (BTS) established the original severity score CURB (confusion, uremia, respiratory rate, low blood pressure) to identify patients with CAP who may be candidates for outpatient vs. inpatient treatment. Inflammatory markers, such as procalcitonin (PCT), can be used to guide management throughout hospital stay. Antibiotic coverage will vary depending on whether outpatient vs. inpatient management is required.

Variation in emergency department diagnostic testing and disposition outcomes in pneumonia

OBJECTIVE

To describe the variability across hospitals in diagnostic test utilization for children diagnosed with community-acquired pneumonia (CAP) during emergency department (ED) evaluation and to determine if test utilization is associated with hospitalization and ED revisits.

METHODS

We conducted a retrospective cohort study of children aged 2 months to 18 years with ED visits resulting in CAP diagnoses from 2007 to 2010 who were seen at 36 hospitals contributing data to the Pediatric Health Information System. Children with complex chronic conditions, recent hospitalization, trauma, aspiration, or perinatal infection were excluded. Primary outcomes included diagnostic testing, hospitalization, and 3-day ED revisit rates across hospitals. We examined variation in diagnostic testing among hospitals by using multivariable mixed-effects logistic regression.

RESULTS

A total of 100,615 ED visits were analyzed. Complete blood count (median: 28.7%), blood culture (27.9%), and chest radiograph (75.7%) were the most commonly ordered ED diagnostic tests. After adjustment for patient characteristics, significant variation (P < .001) was found for each test examined across hospitals. High test-utilizing hospitals had increased odds of hospitalization compared with low-utilizing hospitals (odds ratio: 1.86 [95% confidence interval: 1.17-2.94]; P = .008). However, differences in the odds of ED revisit between the low- and high-utilizing hospitals were not significant (odds ratio: 1.21 [95% confidence interval: 0.97-1.51]; P = .09).

CONCLUSIONS

Emergency departments that use more testing in diagnosing CAP have higher hospitalization rates than lower-utilizing EDs. However, ED revisit rates were not significantly different between high- and low-utilizing EDs. These results suggest an opportunity to reduce diagnostic testing for CAP without negatively affecting outcomes.

Immune regulation of procalcitonin: a biomarker and mediator of infection

Procalcitonin (PCT) has recently emerged as a powerful biomarker for an early and accurate diagnosis of bacterial infection. Here we summarize our current understanding of the expression pathways of PCT, its potential cellular sources including immune cells, and factors inducing its secretion. Also addressed is the significance of increased blood PCT concentration, which may allow this molecule not only to act as a clinical biomarker but also as an active participant in the development and progression of infectious processes. Experimental approaches to delineate a better understanding of PCT functions, molecular pathways that modulate its expression and therapeutic opportunities to curtail its biological actions are discussed, as well.

Recognition and prevention of nosocomial pneumonia in the intensive care unit and infection control in mechanical ventilation

Nosocomial pneumonia (NP) is a difficult diagnosis to establish in the critically ill patient due to the presence of underlying cardiopulmonary disorders (e.g., pulmonary contusion, acute respiratory distress syndrome, atelectasis) and the nonspecific radiographic and clinical signs associated with this infection. Additionally, the classification of NP in the intensive care unit setting has become increasingly complex, as the types of patients who develop NP become more diverse. The occurrence of NP is especially problematic as it is associated with a greater risk of hospital mortality, longer lengths of stay on mechanical ventilation and in the intensive care unit, a greater need for tracheostomy, and significantly increased medical care costs. The adverse effects of NP on healthcare outcomes has increased pressure on clinicians and healthcare systems to prevent this infection, as well as other nosocomial infections that complicate the hospital course of patients with respiratory failure. This manuscript will provide a brief overview of the current approaches for the diagnosis of NP and focus on strategies for prevention. Finally, we will provide some guidance on how standardized or protocolized care of mechanically ventilated patients can reduce the occurrence of and morbidity associated with complications like NP.

Role of calcium in lipopolysaccharide-induced calcitonin gene expression in human adipocytes

Severe systemic infections induce ubiquitous calcitonin (CALC) gene expression with release of calcitonin peptides, namely procalcitonin, calcitonin gene-related peptide and adrenomedullin. Using an in vitro model for bacterial infection, we tested the hypothesis that intracellular calcium concentration ([Ca(2+)](i)) is elevated after lipopolysaccharide (LPS) stimulation and is responsible for the LPS-mediated increase in CALC gene expression and protein secretion. In our human adipocyte model, LPS did not show any cytotoxic effects and induced increased CALC-I gene mRNA expression. Additionally, LPS provoked an elevation in [Ca(2+)](i). The LPS-induced increase in CALC-I gene mRNA was partially blocked with verapamil, an L-type calcium channel blocker and blocked almost completely with 2-aminoethoxydiphenyl borate, a blocker of store-operated calcium entry and inositol triphosphate-mediated calcium release. Treatment of cells with substances elevating [Ca(2+)]( i) led to an increased CALC-I mRNA expression level. The combination of LPS with substances raising [Ca(2+)](i) even potentiated this increase. At the same time, elevated [Ca(2+)](i) attenuated the expression level of the CALC-V gene. These findings indicate that, in human adipocytes, changes in [Ca(2+)](i) are involved in LPSregulated expression of CALC genes, thereby strengthening previous findings postulating a crucial role of intracellular calcium homeostasis in the state of bacterial infection and sepsis.

Occult pneumonia in infants with high fever without source: a prospective multicenter study

BACKGROUND

The prevalence of pneumonia in infants with high fever without source (FWS; temperature, > or =39.0 degrees C) and a white blood cell (WBC) count greater than 20 x 10(9)/L (occult pneumonia) has been reported to be 20% before the introduction of the 7-valent pneumococcal conjugated vaccine (PCV7). This is the main reason for carrying out chest x-ray (CXR) on infants with high FWS. The aims of this study were to establish the prevalence of occult pneumonia in well-appearing infants with high FWS (temperature, > or =39.0 degrees C) and a WBC count greater than 20 x 10(9)/L in the era of PCV7 and to analyze the value of WBC, absolute neutrophil count (ANC), and C-reactive protein (CRP) level as predictors of the risk of occult pneumonia in these patients.

PATIENTS AND METHODS

We conducted a multicenter prospective study in 4 pediatric emergency departments including children younger than 36 months with FWS (temperature, > or =39.0 degrees C) and a WBC count higher than 20 x 10(9)/L on whom a CXR was performed in the absence of respiratory findings. Physicians completed a questionnaire when observing the infant, and the attending physician or, when in doubt, the radiologist interpreted the CXR. Multivariable binary logistic regression was used to estimate the adjusted relative influences of the aforementioned factors on the prevalence of radiological pneumonia.

RESULTS

During an entire year (September 2006 to September 2007), we included 188 infants (aged 1-36 months; 56.2% were males) with high FWS and a WBC count greater than 20 x 10(9)/L (range, 20-44.7 x 10(9)/L) on whom a CXR was performed. Of the 188 chest radiographs obtained, 37 (19.7%) were interpreted by the radiologist. Consolidation in the chest radiographs was detected in 25 (13.3%). The probability of an infant with high FWS and WBC of 20 x 10(9)/L or greater having pneumonia was related to 3 of the studied variables: age, ANC, and serum CRP level. The incidence of pneumonia increased with age (odds ratio [OR] of 2.62 for infants >12 months; 95% confidence interval [95% CI], 1.04-6.60), CRP level greater than 100 mg/L (OR, 3.18; 95% CI, 1.19-8.51), and ANC greater than 20 x 10(9)/L (OR, 3.52; 95% CI, 1.37-9.06). White blood cell count was not predictive of occult pneumonia when ANC was taken into account.

CONCLUSIONS

In the era of PCV7, the incidence of pneumonia in infants younger than 36 months with high FWS and WBC count greater than 20 x 10(9)/L seems to be lower than that previously reported. However, this is not a uniform group because the incidence of pneumonia increases in infants older than 12 months and with higher ANC and serum CRP level.

The utility of biomarkers in sorting out the complex patient

Today's patients present with a complexity of illness far more significant than ever before. Risk factors, in particular for cardiovascular, renal, and metabolic diseases, often interact with each other at core pathophysiological levels. Biomarkers are inexpensive tools that may help differentiate disease states in complex patients. Ideal biomarkers are both sensitive and specific to the disease state being examined. Natriuretic peptides are the prototype of ideal biomarkers and are adjuncts for the diagnosis and exclusion of heart failure in the dyspneic patient, especially those presenting with comorbidities such as lung disease. Just as natriuretic peptide levels can be considered the arbiter of congestive heart failure, cardiac troponins are decisive for myocardial necrosis. Novel assays with higher sensitivity will aid in earlier diagnosis, albeit with some decreased specificity. Nevertheless, the patient presenting with comorbidities and atypical symptoms of myocardial infarction will not be arbitrarily sent home. In the future, other novel biomarkers, such as neutrophil gelatinase-associated lipocalin for acute kidney injury, may come to the forefront for diagnosis of disease in the complex patient.

Clinical review: the role of biomarkers in the diagnosis and management of community-acquired pneumonia

In patients with community-acquired pneumonia, traditional criteria of infection based on clinical signs and symptoms, clinical scoring systems, and general inflammatory indicators (for example, leukocytosis, fever, C-reactive protein and blood cultures) are often of limited clinical value and remain an unreliable guide to etiology, optimal therapy and prognosis. Procalcitonin is superior to other commonly used markers in its specificity for bacterial infection (allowing alternative diagnoses to be excluded), as an indicator of disease severity and risk of death, and mainly as a guide to the necessity for antibiotic therapy. It can therefore be viewed as a diagnostic, prognostic, and perhaps even theragnostic test. It more closely matches the criteria for usefulness than other candidate biomarkers such as C-reactive protein, which is rather a nonspecific marker of acute phase inflammation, and proinflammatory cytokines such as plasma IL-6 levels that are highly variable, cumbersome to measure, and lack specificity for systemic infection. Elevated levels of pro-adrenomedullin, copeptin (which is produced in equimolar amounts to vasopressin), natriuretic peptides and cortisol are significantly related to mortality in community-acquired pneumonia, as are other prohormones such as pro-atrial natriuretic peptide, coagulation markers, and other combinations of inflammatory cytokine profiles. However, all biomarkers have weaknesses as well as strengths. None should be used on its own; and none is anything more than an aid in the exercise of clinical judgment based upon a synthesis of available clinical, physiologic and laboratory features in each patient.