Diagnostic value of exhaled nitric oxide in childhood asthma and allergy

Predictive Value of Impulse Oscillometry Combined with Fractional Expiratory Nitric Oxide Test for Asthma in Preschool Children

Objective

Prediction of asthma in preschool children is challenging and lacks objective indicators. The aim is to observe and analyze the variances between impulse oscillometry (IOS) and fractional expiratory nitric oxide (FeNO) in preschool children with wheezing, establish a joint prediction model, and explore the diagnostic value of combining IOS with FeNO in diagnosing asthma among preschool children.

Patients and methods

This study enrolled children aged 3-6 years with wheezing between June 2021 and June 2022. They were categorized as asthmatic (n=104) or non-asthmatic (n=109) after a 1-year follow-up. Clinical data, along with IOS and FeNO measurements from both groups, underwent univariate regression and multiple regression analyses to identify predictive factors and develop the most accurate model. The prediction model was built using the stepwise (stepAIC) method. The receiver operating characteristic curve (ROC), calibration curve, Hosmer-Lemeshow test, and decision curve analysis (DCA) were employed to validate and assess the model.

Results

During univariate analysis, a history of allergic rhinitis, a history of eczema or atopic dermatitis, and measures including FeNO, R5, X5, R20, Fres, and R5-R20 were found to be associated with asthma diagnosis. Subsequent multivariate analysis revealed elevated FeNO, R5, and X5 as independent risk factors. The stepAIC method selected five factors (history of allergic rhinitis, history of eczema or atopic dermatitis, FeNO, R5, X5) and established a prediction model. The combined model achieved an AUROC of 0.94, with a sensitivity of 0.89 and specificity of 0.88, surpassing that of individual factors. Calibration plots and the HL test confirmed satisfactory accuracy.

Conclusion

This study has developed a prediction model based on five factors, potentially aiding clinicians in early identification of asthma risk among preschool children.

Assessment of Fraction of Exhaled Nitric Oxide and Soluble Receptor for Advanced Glycation End Products Biomarkers for Jordanian Asthmatic Children

PURPOSE

Fraction of exhaled nitric oxide (FeNO) and soluble advanced glycation end-product receptor (sRAGE) are proposed as biomarkers of asthma, therefore we sought to assess their use in asthmatic children of Jordan.

PATIENTS AND METHODS

We conducted a case-control study at The University of Jordan Hospital. A total of 141 asthmatic children followed by respiratory pediatricians and 118 healthy children aged 4-18 years were recruited. FeNO was measured by NObreath device and serum sRAGE by ELISA that detect endogenously soluble isoform (esRAGE) and total soluble RAGE (sRAGE).

RESULTS

sRAGE in asthmatic was half of the control (p <0.001). In addition, ratio of esRAGE/sRAGE was two-fold higher in asthmatic (p = <0.001). Neither FeNO nor esRAGE levels were significantly different between groups. FeNO and asthma control test (ACT) score were negatively correlated corrected for age and body mass index (BMI), (r = -0.180, p= 0.034). For the uncontrolled asthma group, esRAGE/sRAGE negatively correlated with ACT score (r = -.329, p = 0.038). Receiver operating curve (ROC) analysis revealed significant predictive value (PV) for sRAGE and esRAGE/sRAGE in asthma detection with area under the curve (AUC) of (0.751 ± 0.031) and (0.711±.033), consequently. However, no biomarker had a significant PV for lack of control.

CONCLUSION

The current study supports utilizing sRAGE as a marker for asthma and present a potential therapeutic target. However, our results indicate that both FeNO and sRAGE have a limited role in the management of asthmatic children or assessment of asthma control.

Methacholine and FeNO Measurement in Patients with Habit Cough

BACKGROUND

Chronic cough is one of the most common symptoms in childhood. Making a definite diagnosis is a challenge for all pediatricians especially in patients when cough is without an organic cause like in habit cough.

PATIENTS AND METHODS

In this retrospective analysis, all electronic outpatient charts of the Division of Allergology and Pneumology, between January 1, 2010 and December 31, 2019 were reviewed in order to study all children with potential habit cough. All children underwent the following diagnostic algorithms, skin prick test (SPT), measurement of fractional exhaled nitric oxide (FeNO), spirometry and methacholine challenge test (MCT). The value of a normal MCT and FeNO measurement for diagnosing habit cough was investigated.

RESULTS

The chart review revealed 482 patients with chronic cough>4 weeks. Of these, 99 (20.5%) with suspected habit cough were collected. 13 patients had to be excluded for other diagnosis and a complete data set was available in 55 patients. 33 (60.0%) of 55 patients were SPT negative and 22 (40.0%) had sensitization to common allergens. Five patients had elevated FeNO≥20 ppb and three showed severe bronchial hyperresponsiveness<0.1 mg methacholine, challenging the diagnosis of habit cough.

CONCLUSION

A normal FeNO and MCT can help confirm the clinical diagnosis of habit cough. However, in patients with positive MCT and/or elevated FeNO habit cough can be present. Especially in patients with elevated FeNO and severe BHR cough variant asthma and eosinophilic bronchitis have to be ruled out.

Recent Diagnosis Techniques in Pediatric Asthma: Impulse Oscillometry in Preschool Asthma and Use of Exhaled Nitric Oxide

Objective measures of lung function are important in the diagnosis and management of asthma. Spirometry, the pulmonary function test most widely used in asthma, requires respiratory maneuvers that may be difficult for preschoolers. Impulse oscillometry (IOS) is a noninvasive method of measuring lung function during tidal breathing; hence, IOS is an ideal test for use in preschool asthma. Fractional exhaled nitric oxide (FeNO) levels correspond to eosinophilic inflammation and predict responsiveness to corticosteroids. Basic concepts of IOS, methodology, and interpretation, including available normative values, and recent findings regarding FeNO are reviewed in this article.

Fractional Exhaled Nitric Oxide for the Diagnosis of Childhood Asthma: a Systematic Review and Meta-analysis

The gold standard for diagnosing asthma in children is based on clinical history of respiratory symptoms, physical examination, and respiratory function testing. Recent advances indicate that a non-invasive measure of airway inflammation, fractional exhaled nitric oxide (FeNO), provides objective data for use in asthma diagnosis. However, the diagnostic performance of FeNO in children with asthma has not been clearly defined. This systematic review and meta-analysis aimed to evaluate the diagnostic accuracy of FeNO in the clinical determination of asthma in children. Databases of PubMed, the Cochrane Library, EMBASE, MEDION, and Web of Science were searched for relevant articles through March 31, 2016. A bivariate model was used for pooling estimates of sensitivity, specificity, diagnostic odds ratio (DOR), and area under the summary receiver operating curves (SROC) as the main diagnostic measures. In total, eight studies met the inclusion criteria, which included 2933 subjects. The pooled estimates of sensitivity, specificity, and DOR for the detection of asthma in children were 0.79 [95 % confidence interval (CI), 0.64-0.89], 0.81 (95 % CI, 0.66-0.90), and 16.52 (95 % CI, 7.64-35.71). The SROC was 0.87 (95 % CI, 0.84-0.90). In brief, FeNO achieves a moderate diagnostic performance in the detection of asthma in children.

Tools in Asthma Evaluation and Management: When and How to Use Them?

The goals of asthma management are accurate diagnosis, prompt initiation of treatment and monitoring of disease progression to limit potential morbidity and mortality. While the diagnosis and management is largely based on history taking and clinical examination, there are an increasing number of tools available that could be used to aid diagnosis, define phenotypes, monitor progress and assess response to treatment. Tools such as the Asthma Predictive Index could help in making predictions about the possibility of asthma in childhood based on certain clinical parameters in pre-schoolers. Lung function measurements such as peak expiratory flow, spirometry, bronchodilator responsiveness, and bronchial provocation tests help establish airway obstruction and variability over time. Tools such as asthma questionnaires, lung function measurements and markers of airway inflammation could be used in combination with clinical assessments to assess ongoing asthma control. Recent advances in digital technology, which open up new frontiers in asthma management, need to be evaluated and embraced if proven to be of value. This review summarises the role of currently available tools in asthma diagnosis and management. While many of the tools are readily available in resource rich settings, it becomes more challenging when working in resource poor settings. A rational approach to the use of these tools is recommended.

Exhaled NO as a predictor of exercise-induced asthma in cold air

PURPOSE

Physical activity is an important part of life, and exercise-induced asthma (EIA) can reduce the quality of life. A standardized exercise challenge is needed to diagnose EIA, but this is a time consuming, effortful and expensive method. Exhaled nitric oxide (eNO) as a marker of eosinophil inflammation is determined rapidly and easily. The aim of this study was to investigate eNO as surrogate marker for predicting a positive reaction in an exercise challenge in a cold chamber (ECC).

METHODS

A total of 143 subjects aged 6-45 years with suspected EIA were recruited for the study. The subjects underwent an eNO measurement, an ECC and a skin prick test (SPT). To define the sensitivity and specificity of eNO as predictor, a receiver-operating characteristic (ROC) curve was plotted. The individual probability of the occurrence of a positive reaction after ECC based on an eNO value was calculated using a logistic regression model.

RESULTS

An eNO cut-off value of 18.5 ppb (area under the curve (AUC) 0.71, p < 0.001) showed the best combination of sensitivity and specificity for a positive reaction (forced expiratory volume in 1 s (FEV₁) decrease ≥ 10% after ECC) for the whole group. An eNO cut-off value of 46.0 ppb had a specificity of 100.0% to predict a significant FEV₁ decrease and may save exercise testing in 22.4% of patients. A negative predictive level with a high sensitivity and negative predictive value (NPV) could not be defined. In the subgroup that was house dust might (HDM) allergy positive (HDM pos; n = 68, 45.5% of all subjects), an eNO cut-off value of 35.5 ppb (AUC 0.79, p < 0.01) showed the best combination of sensitivity and specificity for a positive reaction after the ECC with a specificity 100.0% and may save exercise testing in 45.6% of HDM pos patients. Using logistic regression, a 95% probability for a positive FEV₁ decrease after ECC was estimated at 53 ppb for the whole group and at 47 ppb for the HDM pos subgroup.

CONCLUSIONS

Exhaled NO measurement is a screening tool for EIA, especially in HDM pos subjects. In a real-life setting, a cut-off value of 46.0 ppb detects EIA at 100% in all suspected patients, and a cut-off level of 35.5 ppb is valuable marker of EIA in patients with an HDM allergy. These levels can save time and costs in a large proportion of patients and will be helpful for clinicians.

Status of selected ion flow tube MS: accomplishments and challenges in breath analysis and other areas

This article reflects our observations of recent accomplishments made using selected ion flow tube MS (SIFT-MS). Only brief descriptions are given of SIFT-MS as an analytical method and of the recent extensions to the underpinning analytical ion chemistry required to realize more robust analyses. The challenge of breath analysis is given special attention because, when achieved, it renders analysis of other air media relatively straightforward. Brief overviews are given of recent SIFT-MS breath analyses by leading research groups, noting the desirability of detection and quantification of single volatile biomarkers rather than reliance on statistical analyses, if breath analysis is to be accepted into clinical practice. A 'strengths, weaknesses, opportunities and threats' analysis of SIFT-MS is made, which should help to increase its utility for trace gas analysis.

Exhaled nitric oxide in school children: Searching for the lost variability

OBJECTIVE

The factors - including asthma and rhinoconjunctivitis - which influence FeNO values in a general population of school children have been studied in order to know to what extent the variability of those values can be explained.

METHODS

FeNO was measured in a population of 240 school children aged 6-12 years by means of a Niox-Mino™ device in a standardised way. Parents filled in an ISAAC-validated questionnaire of symptoms and environmental factors. Diagnoses were checked against clinical records. Height and weight were measured. A multivariate regression analysis including all variables in the questionnaire was performed, which was followed by two Xi stepwise tests in order to build a predictive model which included the main variables influencing FeNO values.

RESULTS

Among the 240 children, 10 suffered from asthma, 16 from rhinoconjunctivitis and 15 from both conditions. FeNO values (GM±GSD) in children with rhinoconjunctivitis (19.61±1.20ppb), with asthma (18.62±1.32ppb), and with both conditions (17.62±1.19ppb) tended to be significantly higher than control children (11.42±1.04ppb), p=0.0016, p=0.08 and p=0.01, respectively. The different predictive models were able to explain only 20-27% of FeNO variability.

CONCLUSIONS

The proportion of FeNO inter-individual variability which can be explained by individual (including suffering from asthma or rhinoconjunctivitis), family, and environmental factors is very low (20-27%). This could have implications on the usefulness of FeNO as a diagnostic tool in asthma.

Exhaled nitric oxide decreases during exercise in non-asthmatic children

INTRODUCTION

Exhaled nitric oxide (FENO) measurements are recommended to be performed before spirometry and exercise challenge tests because forced breathing might influence FENO values. Information on the effect of exercise on FENO is lacking in non-asthmatic children.

AIM

  To investigate the effect on FENO of a standardized exercise challenge test on a treadmill in non-asthmatic children with and without allergic rhinoconjunctivitis (AR) symptoms.

METHODS

From the case-control study 'Asthma and allergy among school children in Nordland', 330 non-asthmatic pupils age 8-16 years were enrolled. FENO was measured at baseline and at 1 min and 30 min after exercise challenge test by the single breath technique with EcoMedics Exhalazer® (Eco Physics, Duernten, Switzerland).

RESULTS

Pair-wise comparison of FENO from baseline demonstrated a highly significant reduction in FENO post-exercise for all children at 1 min (27.4%) and at 30 min (16.1%) (P < 0.001). The AR group had a significantly higher decline in FENO value at 1 min post-exercise compared to the non-AR group, 4.2 parts per billion (ppb) vs 2.6 ppb (P < 0.001). Decline in FENO immediately post-exercise was more significant if baseline FENO was ≥ 20 ppb; mean reduction 9.9 (95% CI: 8.7-11.4) ppb.

CONCLUSION

FENO is reduced by 27.4% immediately after a standardized treadmill exercise test in non-asthmatic children. Pupils reporting AR symptoms demonstrate a larger decline in FENO value at 1 min post-exercise compared to pupils without AR symptoms. These findings confirm that children should refrain from physical activity before FENO measurement.

Indoor Fungal Exposure and Allergic Respiratory Disease

A gathering body of evidence has repeatedly revealed associations between indoor fungi and initiation, promotion, and exacerbation of allergic respiratory disease. The relationship between the exposure and outcome are complicated by the difficulties in measuring both exposure and outcome, the multifactorial nature of the disease, and the wide range of potential confounders. New technologies are becoming available that may enable better measurement of exposure and tighter case definitions so as to build more confidence in the associations discovered. The growing strength of the evidence base will aid the design of future public health interventions and generate new hypotheses on the cause of the rapid increase in allergic respiratory disease prevalence.

An Overview of Fractional Exhaled Nitric Oxide and Children with Asthma

Asthma is the most common pediatric chronic disease and is characterized by lung inflammation. Fractional exhaled nitric oxide (FeNO) is thought to reflect the presence of eosinophilic airway inflammation, and is an easy, non-invasive test that has held promise in providing additional objective data. However, not all studies have shown a clinical benefit in the use of FeNO to guide management of asthma in children. This review will describe the results of the most recent studies examining the use of FeNO in the diagnosis and treatment of asthma in infants, preschool-aged children and in school-aged children. It will aid the clinician in providing a clinical context in which FeNO may be most useful in treating pediatric asthma.

Validation of a questionnaire against clinical assessment in the diagnosis of asthma in school children

AIM

A questionnaire has been used repeatedly in cross-sectional studies to determine the prevalence of asthma, allergic rhinoconjunctivitis (AR) and eczema among schoolchildren in Nordland County, Norway. The current study was designed to validate the questionnaire against clinical assessment as the diagnostic gold standard and to investigate the extent of possible misclassification.

METHODS

A subsample of 801 schoolchildren of 4150, whose parents had answered a questionnaire covering asthma and atopic diseases, underwent a detailed clinical evaluation including a standardized interview, a clinical examination, skin prick tests (SPT), blood samples, spirometry an exercise treadmill test (EIB test) and measurement of exhaled nitrogen oxide (FeNO).

RESULTS

The questionnaire had a sensitivity of 0.96 and a specificity of 0.87 for the diagnosis of asthma ever compared to clinical assessment. The overall agreement (kappa) was 0.80. After clinical assessment the prevalence of asthma ever was adjusted from 17.6 % to 16.9 % (95% CI: 15.8-18.0). The most sensitive and specific questions in identifying asthmatic children by the questionnaire were questions asking about diagnosis ('Has the child ever had asthma?') rather than those covering asthma symptoms such as wheeze, shortness of breath and/or cough. A positive exercise test increased the post-test probability for the asthma diagnosis only to a minimal degree.

CONCLUSION

Based on the good agreement between the questionnaire responses and the clinical assessments, it is concluded that the questionnaire had good validity and served as a useful epidemiological tool. Detailed clinical testing added little additional information.

Establishing IMMULITE® 2000 cut-off values for serum allergen-specific immunoglobulin and exploring their relationship to exhaled nitric oxide

Aim

Paediatric cut-off values for serum allergen-specific IgE (sIgE) using the Siemens IMMULITE® 2000 system to diagnose allergic rhinoconjunctivitis have not been established. We aimed to determine cut-off levels for sIgE for 10 common inhalant allergens and to study the relationship between sIgE, total IgE and fractional exhaled nitric oxide (FE_NO).

Methods

We enrolled 243 schoolchildren, including 164 with allergic rhinoconjunctivitis. Parental interviews, skin prick tests, sIgE, total IgE, FE_NO measurements, spirometry and exercise tests were performed.

Results

Cut-off values with the best combined sensitivity and specificity were above the detection limit of the assay for seven of the ten allergens (0.23–1.1 kU/L). The overall accuracy of the IMMULITE® in detecting allergic rhinoconjunctivitis was good. sIgE was superior to total IgE and FE_NO in predicting allergic rhinoconjunctivitis to timothy, birch, mugwort, cat, dog and house dust mite. FE_NO was elevated in children with allergic rhinoconjunctivitis, irrespective of asthma.

Conclusion

Cut-off values for sIgE were dependent on the allergic phenotype and were above the IMMULITE® detection limit for seven of ten inhalant allergens. Consequently, using the detection limit for sIgE as the decision point would result in over-diagnosing allergic rhinoconjunctivitis. When measuring elevated FE_NO in children, allergic rhinoconjunctivitis should be suspected.

Asthma with allergic comorbidities in adolescence is associated with bronchial responsiveness and airways inflammation

BACKGROUND

Childhood asthma frequently has allergic comorbidities. However, there is limited knowledge of the longitudinal development of asthma comorbidites and their association to bronchial hyper-responsiveness (BHR) and airway inflammation markers. We therefore aimed to assess the association between childhood asthma with allergic comorbidities and BHR and fractional exhaled nitric oxide (FE(NO)) and the impact of gender on these associations.

METHODS

Based on data from 550 adolescents in the prospective birth cohort 'Environment and Childhood Asthma' study, asthma was defined for the three time periods 0-2, 2-10 and 10-16 years of age, using recurrent bronchial obstruction (rBO) 0-2 years of age as a proxy for early asthma. Asthma comorbidities included atopic dermatitis (AD) and allergic rhinitis (AR) from 10 to 16 years. At age 16 years BHR, assessed by metacholine bronchial challenge, and airway inflammation, assessed by FE(NO), were compared between the groups of asthma with or without the two comorbidities, to a reference group with no never asthma, and subsequently stratified by gender.

RESULTS

Boys with asthma and AR, regardless of AD had significantly more severe BHR and higher FE(NO) than the other asthma phenotypes. Almost half of the children remained in the asthma and AR category from 10 to 16 years, the entire difference being determined by new incident cases from 10 to 16 years.

CONCLUSIONS

Asthma phenotypes characterized by allergic comorbidities and AR in particular appears closely associated with BHR and FE(NO), especially among boys.

Exhaled nitric oxide is related to atopy, but not asthma in adolescents with bronchiolitis in infancy

Background

The fraction of exhaled nitric oxide (FeNO) has been suggested as a non-invasive marker of eosinophilic inflammation in asthma, but lately rather as a biomarker of atopy than of asthma itself. Asthma after bronchiolitis is common up to early adolescence, but the inflammation and pathophysiology may differ from other phenotypes of childhood asthma. We aimed to assess if FeNO was different in children with former hospitalization for bronchiolitis and a control group, and to explore whether the role of FeNO as a marker of asthma, atopy or bronchial hyperresponsiveness (BHR) differed between these two groups of children.

Methods

The study included 108 of 131 children (82%) hospitalized for bronchiolitis in 1997–98, of whom 82 (76%) had tested positive for Respiratory syncytial virus, and 90 age matched controls. The follow-up took place in 2008–2009 at 11 years of age. The children answered an ISAAC questionnaire regarding respiratory symptoms and skin prick tests, spirometry, methacholine provocation test and measurement of FeNO were performed.

Results

Analysed by ANOVA, FeNO levels did not differ between the post-bronchiolitis and control groups (p = 0.214). By multivariate regression analyses, atopy, height (p < 0.001 for both) and BHR (p = 0.034), but not asthma (p = 0.805) or hospitalization for bronchiolitis (p = 0.359), were associated with FeNO in the post-bronchiolitis and control groups. The associations for atopy and BHR were similar in the post-bronchiolitis and in the control group.

Conclusion

FeNO did not differ between 11 year old children hospitalized for bronchiolitis and a control group. FeNO was associated with atopy, but not with asthma in both groups.

Office-based exhaled nitric oxide measurement in children 4 years of age and older

BACKGROUND

Fractional exhaled nitric oxide (FENO) is increasingly being used in the office-based management of asthma, but data in children are limited.

OBJECTIVES

To report FENO values in 4- to 7-year-old children with suspected asthma and characterize their relation to clinical variables and describe the relation among FENO levels, age, and sex in 4- to 18-year-old children with suspected asthma.

METHODS

Retrospective data in 4- to 18-year-old children (n = 825) who underwent FENO testing using the NIOX MINO device were collected and analyzed. Chart reviews were performed for the 4- to 7-year-old children (n = 75).

RESULTS

FENO values ranged from less than or equal to 5 to 89 ppb in 75 4- to 7-year-old children and less than or equal to 5 to 300 ppb in 750 > 7 to 18-year-old children. Approximately one tenth of 4- to 7-year-old children and one third of > 7 to 18-year-old children had FENO values indicative of eosinophilic/allergic inflammation (>35 ppb). In regression analysis of the 4- to 7-year-old children, increasing age (P = .03) and asthma severity (P = .01) were associated with higher FENO levels. Atopic dermatitis was significantly associated (P = .03), whereas allergic rhinitis was marginally associated (P = .06), with higher FENO levels. Inhaled corticosteroid use was associated with lower FENO levels (P = .02).

CONCLUSION

This study characterizes the largest cohort of 4- to 7-year-old children to undergo FENO testing in ambulatory asthma management. Correlations between FENO levels and clinical variables were consistent with established findings in older children. This preliminary real-world study suggests that FENO assessment may be feasible and useful in the office-based asthma management of children as young as 4 years.

Fraction of exhaled nitric oxide and wheezing phenotypes in preschool children

BACKGROUND

Asthma is a chronic lower airway inflammatory disease. Nitric oxide is an inflammatory mediator produced endogenously in the airway. Previous studies have demonstrated that the fractional concentration of exhaled nitric oxide (FeNO) is increased in asthma.

OBJECTIVES

To investigate if FeNO concentrations were correlated with wheezing phenotypes in preschool children and to compare the FeNO results with airway hyperresponsiveness (AHR) and pulmonary function test (PFT) results.

METHODS

We performed skin prick tests, methacholine provocation tests, PFT, impulse oscillometry bronchodilator response (IOS BDR) tests, and FeNO measurements in 372 preschool children between the ages of 4 and 6 years. Wheezing phenotypes were defined according to the age of onset and persistency.

RESULTS

Persistent wheezers had higher FeNO levels than transient wheezers and non-wheezers. Among persistent wheezers, those with atopy and AHR had significantly higher FeNO levels than those without atopy or AHR. FeNO levels were significantly higher in late-onset wheezers than early-onset wheezers and non-wheezers. Among late-onset wheezers, those with atopy and AHR had a significantly higher FeNO concentration than those without atopy or AHR as well as those with either atopy or AHR. However, there were no significant differences in AHR, PFT, or IOS BDR between persistent and transient wheezers or between late-onset wheezers and early-onset wheezers.

CONCLUSION

FeNO may be a better marker for asthma phenotypes in preschool children than AHR and PFT results.

On the features, successes and challenges of selected ion flow tube mass spectrometry

The major features of the selected ion flow tube mass spectrometry (SIFT-MS) analytical method that was conceived and designed for the analysis, in real time, of air obviating sample collections into bags or extraction by pre-concentration of trace compounds onto surfaces are reviewed. The unique analytical capabilities of SIFT-MS for ambient analysis are stressed that allow quantification of volatile organic and inorganic compounds directly from the measurement of physical parameters without the need for regular instrumental calibration using internal or external standards. Then, emphasis is placed on the challenging real-time accurate analysis of single exhalations of humid breath, which is now achieved and readily facilitates wider applications of SIFT-MS in other fields where trace gas analysis has value. The quality of the data obtained by SIFT-MS is illustrated by the quantification of some exhaled breath metabolites that are of immediate relevance to physiology and medicine, including that of hydrogen cyanide in the breath of patients with cystic fibrosis. The current status of SIFT-MS is revealed by a form of a strengths, weakness, opportunities and threats (SWOT) analysis intended to present an objective view of this analytical technique and the likely way forward towards its further development and application.

Clinical application of exhaled nitric oxide measurement in pediatric lung diseases

Fractional exhaled nitric oxide (FeNO) is a non invasive method for assessing the inflammatory status of children with airway disease. Different ways to measure FeNO levels are currently available. The possibility of measuring FeNO levels in an office setting even in young children, and the commercial availability of portable devices, support the routine use of FeNO determination in the daily pediatric practice. Although many confounding factors may affect its measurement, FeNO is now widely used in the management of children with asthma, and seems to provide significantly higher diagnostic accuracy than lung function or bronchial challenge tests. The role of FeNO in airway infection (e.g. viral bronchiolitis and common acquired pneumonia), in bronchiectasis, or in cases with diffuse lung disease is less clear. This review focuses on the most recent advances and the current clinical applications of FeNO measurement in pediatric lung disease.

Fractional exhaled nitric oxide in healthy non-asthmatic 7-year olds and prenatal exposure to polycyclic aromatic hydrocarbons: nested regression analysis

The main goal of the study was to assess possible association between transplacental exposure to genotoxic PAH compounds assessed by the cord blood PAH-DNA adducts and fractional exhaled nitric oxide (FeNO) measured in healthy non-asthmatic children at the age of 7 years. The subjects included the subsample of 89 children who took part in the ongoing population based birth cohort study in Krakow and attended FeNO testing. The effect of transplacental PAH exposure was adjusted for potential confounders, such as maternal allergy and children's specific atopy to common domestic allergens.

RESULTS

FeNO values were significantly elevated in children with higher prenatal PAH exposure (gmean = 7.7 ppb; 95% CI: 5.8-10.2 ppb) compared with those at low exposure level (gmean = 3.8 ppb; 95% CI: 2.3-6.3) (P = 0.011). Children with maternal allergy had also significantly higher mean FeNO values (gmean = 13.7 ppb, 95% CI: 8.8-21.4 ppb) compared with the subjects whose mothers denied allergy (gmean = 5.6 ppb, 95% CI: 4.3-7.3 ppb) (P = 0.012). Similarly, FeNO values in atopic children were higher (gmean = 11.2 ppb; 95% CI: 3.8-32.8 ppb) than in non-atopic individuals (gmean = 6.0 ppb; 95% CI: 4.7-7.7 ppb, P = 0.079). The results of the nested multivariable linear regression analysis showed that both maternal allergy and sensitization of children to domestic aeroallergens jointly explained 10.4% of FeNO variance, however, the additional 10.9% was determined by prenatal PAH exposure.

CONCLUSION

FeNO is more than a marker useful for screening atopy or symptomatic bronchial inflammation and may also be a proxy for cytokine deregulation and "allergic response" phenotype possibly established in fetal period due to transplacental PAH exposure. Preliminary results of our study should encourage more studies on intrauterine PAH exposure and later respiratory symptoms.

Alveolar concentration and bronchial flux of nitric oxide: two linear modeling methods evaluated in children and adolescents with allergic rhinitis and atopic asthma

OBJECTIVE

Alveolar concentration (C(A)NO) and bronchial flux (J(aw)NO) of nitric oxide (NO) characterize the contributions of peripheral and proximal airways to exhaled NO. Both parameters can be estimated using a two-compartment model if the fraction of NO in orally exhaled air (FE(NO)) is measured at multiple constant expiratory flow rates (V). The aim of this study was to evaluate how departures from linearity influence the estimates of C(A)NO and J(aw)NO obtained with the help of linear regression analysis of the relationships between FE(NO) and 1/V (method P), and between the NO output (V(NO) = FE(NO) × V) and V (method T). Furthermore, differences between patients with atopic asthma (AA) and allergic rhinitis (AR) and between methods P and T were assessed.

DESIGN

Measurements of FE(NO) were performed with a chemiluminiscence analyzer at five levels of V ranging from 50 to 250 ml/sec in school children and adolescents with mild to moderate-severe AA treated by inhaled corticosteroids (N = 42) and AR (N = 20).

RESULTS

Violation of the linearity condition at V ≤ 100 ml/sec caused shifts between methods with regard to the partition of exhaled NO into alveolar (C(A)NO: P > T) and bronchial (J(aw)NO: T > P) components. Both methods gave similar results in the linear range of 150-250 ml/sec: The mean ratios P/T and limits of agreement calculated in AA and AR patients were 1.03 (0.49-1.56) and 1.07 (0.55-1.59) for C(A)NO and 1.03 (0.73-1.33) and 0.99 (0.90-1.10) for J(aw)NO, respectively. No significant differences between AA and AR were found in C(A)NO and J(aw)NO calculated in the linear range by the T method {medians (inter-quartile ranges): 1.7 ppb (0.9-3.9) vs. 2.3 ppb (0.8-3.7), P = 0.91; 1,800 pl/sec (950-3,560) vs. 1,180 pl/sec (639-1,950), P = 0.061}. However, the flow-dependency of the estimates was markedly higher in AA than in AR patients: C(A) NO was decreased 2.8-fold vs. 1.5-fold and J(aw) NO was increased 1.5-fold vs. 1.2-fold in the linear range as compared to the range of 50-250 ml/sec. In both groups, the median standard errors (SE) of the J(aw) NO estimates were similar for the metods P and T and small (<15%) regardless of the range for expiratory flows. The precision of C(A) NO estimates was less in all ranges. For both methods, the SE of the estimates obtained in the range of 150-250 ml/sec exceeded 50% in asthmatics and 30% in AR patients, respectively. The results show that FE(NO) has to be measured at several expiratory flows ≥100 ml/sec for the accurate estimation of C(A) NO and J(aw) NO using linear methods P and T in children and adolescents with AA and AR. A stepwise procedure for detecting nonlinearity and evaluating the quality of FE(NO) measurements is suggested.

Identifying uncontrolled asthma in children with the childhood asthma control test or exhaled nitric oxide measurement

BACKGROUND

International guidelines highlight the importance of assessing asthma control status in children with asthma, and research on practical and objective instruments for assessing asthma control is ongoing.

OBJECTIVE

To determine the role of the Childhood Asthma Control Test (C-ACT) and fractional concentration of exhaled nitric oxide (FeNO) in identifying children with not well-controlled asthma.

METHODS

Children 6 to 11 years of age with asthma were enrolled in the study. They completed C-ACT and underwent FeNO and spirometric measurements during the monthly clinic visits. An asthma specialist assessed asthma control according to the gold standard Global Initiative for Asthma guideline and decided the treatment of the patients.

RESULTS

Seventy-six children with a mean (SD) age of 8.7 (1.4) years were evaluated in the first visit, whereas 64 and 51 children were admitted for second and third visits, respectively. A C-ACT score of 22 or less had 69% sensitivity and 77% specificity in determining not well-controlled asthma, whereas an FeNO value of 19 ppb or higher had 61% sensitivity and 59% specificity in patients who completed 3 visits. Receiver operating characteristic curve analysis revealed that the C-ACT was better than FeNO for identifying patients with not well-controlled asthma (area under the curve, 0.79; P < .001 [C-ACT] vs .58, P = .10 [FeNO]) Results of multivariate generalized estimating equation analysis revealed that a C-ACT score of 22 or less (odds ratio, 8.75; 95% confidence interval, 4.35-17.59; P < .001) and an FeNO of 19 ppb or greater (odds ratio, 2.60; 95% confidence interval, 1.07-6.29; P = .03) were significant indicators for the presence of not well-controlled asthma.

CONCLUSION

The C-ACT is superior to FeNO in determining the control status of children with asthma and may be used as a complementary tool in clinical practice to detect children with not well-controlled asthma.

Time spent in vigorous physical activity is associated with increased exhaled nitric oxide in non-asthmatic adolescents

INTRODUCTION

Physical activity (PA) is important in preventing disease, but endurance elite athletes have increased prevalence of asthma and airway inflammation.

OBJECTIVES

We aimed to determine if PA was associated with increased fractional exhaled nitric oxide (FENO ) in asthmatic and non-asthmatic adolescents.

METHODS

FENO was recorded (Niox Mino®, Aerocrine AB, Stockholm, Sweden) in 169 adolescents (13-14 years) in a nested case-control analysis from the Environment and Childhood Asthma study, Oslo, 92 adolescents with and 77 without asthma. They underwent clinical examination, lung function measurements and treadmill run measuring peak oxygen uptake, and objectively recorded PA for four consecutive days. PA was classified as moderate, vigorous and very vigorous, and total number of hours of each category was recorded for each subject. Associations between FENO and PA were tested using linear robust multiple regression analyses.

RESULTS

In non-asthmatic adolescents, FENO was associated with daily hours of vigorous to very vigorous (r=0.27, P=0.02) and very vigorous PAs (r=0.25, P=0.036) in bivariate analyses. In multivariate analyses, FENO was associated with vigorous to very vigorous PA [regression coefficients (95% confidence interval) 1.9 (0.6, 3.1); P=0.004] and more strongly with very vigorous PA [3.9 (1.5, 6.4); P=0.002] in non-asthmatic but not in asthmatic adolescents. Total daily PA was not associated with FENO in either group. Thus, 1 h of very vigorous PA per day increased FENO by 3.9ppb.

CONCLUSION

Vigorous to very vigorous PA, contrasting total daily PA, was significantly associated with increased FENO in non-asthmatic adolescents, suggesting that intensive PA may induce airway inflammation independent of asthma.

Volatile compounds in health and disease

PURPOSE OF REVIEW

To summarize the recent progress made in noninvasive monitoring of volatile compounds in exhaled breath and above biological liquids, as they are becoming increasingly important in assessing the nutritional and clinical status and beginning to provide support to conventional clinical diagnostics and therapy. To indicate the potential of these developments in medicine and the specific areas which are currently under investigation.

RECENT FINDINGS

The significance of the following breath gases and their concentrations are reported: acetone and the influence of diet; ammonia confirmed as an indicator of dialysis efficacy; hydrogen and the (13)CO(2)/(12)CO(2) ratio (following the ingestion of (13)C-labeled compounds) as related to gastric emptying and bowel transit times; hydrogen cyanide released by Pseudomonas and its detection in breath of children with cystic fibrosis; and multiple trace compounds in breath of patients with specific pathophysiological conditions and 'metabolic profiling'.

SUMMARY

Advanced analytical methods, especially exploiting mass spectrometry, are moving breath analysis towards the clinical setting; some trace gas metabolites are already being exploited in diagnosis and therapy. Much effort is being given to the search for biomarkers of tumours in the body. HCN as an indicator of the presence of Pseudomonas in the airways has real potential in therapeutically alleviating the symptoms of cystic fibrosis.

Altered oxidative state in schoolchildren with asthma and allergic rhinitis

Oxidative stress may be defined as a disruption of the balance between the level of oxidants and reductants (antioxidants), and oxidative state in children may influence the risk of asthma and allergic disease. We investigated serum antioxidant levels: selenium, vitamin E, bilirubin, albumin, uric acid and transferrin as well as the oxidant ferritin and their association with asthma and allergic rhinitis. Children of 7-12 yr with asthma (n = 50) and no asthma (controls) (n = 52) underwent skin prick test, lung function, fractional exhaled nitric oxide (FeNO) measurements and blood sampling. Allergic rhinitis was found in 23 children, 19 with asthma and four controls. Healthy children were controls without rhinitis. Asthma was associated with reduced albumin (g/l), adjusted odds ratio (aOR) (95% CI) 0.81 (0.66, 0.99) (p = 0.048) compared with healthy children in a regression analysis adjusted for age and gender. Asthma with high FeNO ≥20 ppb was associated with reduced albumin, aOR 0.60 (0.40, 0.89) (p = 0.012) compared to controls with FeNO <20. Asthma with allergic rhinitis had reduced albumin, aOR = 0.70 (0.50, 0.99) (p = 0.04), and higher ferritin levels (mg/l) [aOR = 1.04 (1.00, 1.09) p = 0.03] compared to healthy children. Poorly controlled asthma was associated with lower vitamin E levels, aOR 0.79 (0.65, 0.95) (p = 0.02), lower transferrin levels, aOR 0.72 (0.57, 0.92) (p < 0.01), and higher albumin levels, aOR 1.53 (1.03, 2.28) (p = 0.04), compared to well controlled asthma. In conclusion, schoolchildren with asthma and rhinitis had reduced levels of the major serum antioxidant albumin, and poorly controlled asthma was associated with decreased vitamin E and transferrin levels. Reduced albumin was associated with increased FeNO, a marker of allergic inflammation in asthma, although the discriminatory value of this finding should be further assessed in population studies.

Paracetamol in early infancy: the risk of childhood allergy and asthma

AIM

We investigated whether paracetamol exposure in pregnancy and until 6 months of age was associated with allergic disease in school children.

METHODS

In a prospective birth cohort study in Oslo, 1016 children included at birth were re-investigated at 10 years. Paracetamol exposure in pregnancy and until 6 months of age was registered. Outcomes at 10 years included current asthma, a history of asthma, allergic sensitization and allergic rhinitis.

RESULTS

Maternal paracetamol use in the first trimester increased the risk for allergic rhinitis at 10 years OR (odds ratio) (95%CI) 2.30 (1.06, 4.97) in boys and girls. Paracetamol use until 6 months in girls increased the risk for allergic sensitization OR 2.20 (1.15, 4.22) and a history of asthma OR 2.20 (1.13, 4.30). The ORs for allergic sensitization and history of asthma in girls remained unchanged adjusting for upper or lower airway infections during the first 6 months of life.

CONCLUSION

Paracetamol exposure in pregnancy was associated with allergic rhinitis, but not with asthma or allergic sensitization at 10 years of age. Paracetamol used until 6 months of age was associated with allergic sensitization and having a history of asthma in girls at 10 years of age, even considering concomitant airway infections.

Gender differences in indoor allergen exposure and association with current rhinitis

BACKGROUND

Differences between boys and girls in allergic manifestations are well known, and this difference is possibly not attributed to physiological differences alone.

OBJECTIVE

We, therefore, investigated whether boys and girls could be exposed to different allergen levels at home and whether indoor allergen levels could be differently associated with rhinitis in boys and girls at 10 years of age.

METHODS

Cat, dog and house dust mite (HDM) allergen levels in mattress dust and interview data regarding current allergic disease were available for 797 10-year-old children (360 girls) in The Environment and Childhood Asthma Study in Oslo.

RESULTS

Girls had higher concentrations of cat and dog allergens in their mattresses compared with boys, also in homes without cats [geometric mean 95% confidence intervals (95% CI): 0.37 (0.31, 0.44) for girls and 0.26 (0.23, 0.30) microg cat allergen/g dust for boys, P=0.002], and without dogs [girls: 0.74 (0.63, 0.86) and boys: 0.55 (0.48, 0.62) microg dog allergen/g dust, P=0.003]. No difference was observed for HDM allergen (Der p 1) levels. Of the 190 (23.8%) children reporting current rhinitis, 144 (75.8%) were sensitized to at least one allergen. The adjusted odds ratio for current rhinitis increased with 1.20 (95% CI: 1.01, 1.42) per 1 microg/g dust increase in Der p 1 for girls (P=0.037), but not for boys (P=0.91).

CONCLUSION

Girls had higher levels of cat and dog allergens in mattress dust compared with boys, whereas no difference was observed for Der p 1 allergen. Nevertheless, only increasing levels of Der p 1 and not cat and dog allergens significantly increased the risk of current rhinitis in girls, whereas no significant association was observed for boys.