An Overview of Fractional Exhaled Nitric Oxide and Children with Asthma

Advances in non-type 2 severe asthma: from molecular insights to novel treatment strategies

Asthma is a prevalent pulmonary disease that affects more than 300 million people worldwide and imposes a substantial economic burden. While medication can effectively control symptoms in some patients, severe asthma attacks, driven by airway inflammation induced by environmental and infectious exposures, continue to be a major cause of asthma-related mortality. Heterogeneous phenotypes of asthma include type 2 (T2) and non-T2 asthma. Non-T2 asthma is often observed in patients with severe and/or steroid-resistant asthma. This review covers the molecular mechanisms, clinical phenotypes, causes and promising treatments of non-T2 severe asthma. Specifically, we discuss the signalling pathways for non-T2 asthma including the activation of inflammasomes, interferon responses and interleukin-17 pathways, and their contributions to the subtypes, progression and severity of non-T2 asthma. Understanding the molecular mechanisms and genetic determinants underlying non-T2 asthma could form the basis for precision medicine in severe asthma treatment.

Severe Acute Bronchial Asthma with Sepsis: Determining the Status of Biomarkers in the Diagnosis of the Disease

Bronchial asthma is a widely prevalent illness that substantially impacts an individual's health standard worldwide and has a significant financial impact on society. Global guidelines for managing asthma do not recommend the routine use of antimicrobial agents because most episodes of the condition are linked to viral respiratory tract infections (RTI), and bacterial infection appears to have an insignificant impact. However, antibiotics are recommended when there is a high-grade fever, a consolidation on the chest radiograph, and purulent sputum that contains polymorphs rather than eosinophils. Managing acute bronchial asthma with sepsis, specifically the choice of whether or not to initiate antimicrobial treatment, remains difficult since there are currently no practical clinical or radiological markers that allow for a simple distinction between viral and bacterial infections. Researchers found that serum procalcitonin (PCT) values can efficiently and safely minimize antibiotic usage in individuals with severe acute asthma. Again, the clinical manifestations of acute asthma and bacterial RTI are similar, as are frequently used test values, like C-reactive protein (CRP) and white blood cell (WBC) count, making it harder for doctors to differentiate between viral and bacterial infections in asthma patients. The role and scope of each biomarker have not been precisely defined yet, although they have all been established to aid healthcare professionals in their diagnostics and treatment strategies.

Longitudinal measures of phthalate exposure and asthma exacerbation in a rural agricultural cohort of Latino children in Yakima Valley, Washington

Phthalates are a class of widely used synthetic chemicals found in commonly used materials and products. Epidemiological studies suggest phthalate exposure is associated with asthma outcomes, though most studies have not investigated phthalates as triggers of exacerbations in children diagnosed with asthma. This study used data from the Home Air in Agriculture Pediatric Intervention Trial (HAPI) to examine relationships between phthalate exposure and outcomes related to childhood asthma exacerbation. We used measures of phthalate metabolites and respiratory health measures including fractional exhaled nitric oxide (FENO), the Asthma Control Test (ACT), caregiver report of symptoms, and urinary leukotriene E₄ (uLTE₄) to estimate longitudinal associations using mixed effects models, adjusted for covariates. For 100% (i.e., doubling) increases in mono-(2-ethyl-5-carboxypentyl) phthalate (MECPP), mono-2-ethylhexyl phthalate (MEHP), and mono-ethyl phthalate (MEP), concentrations of FENO increased by 8.7% (95% CI: 0.7-17.3), 7.2% (95% CI: 0.0-14.9), and 6.4% (95% CI: 0.0-13.3), respectively. All phthalate metabolites demonstrated associations with uLTE₄, effect sizes ranging from an 8.7% increase in uLTE₄ (95% CI: 4.3-12.5) for a 100% increase in MEHP to an 18.1% increase in uLTE₄ (95% CI: 13.3-23.1) for a 100% increase in MNBP. In models of caregiver report of symptoms, no phthalate metabolites were significantly associated in primary models. No phthalate metabolites were associated with standardized ACT score. Our results suggest urinary phthalate metabolites are significant predictors of inflammatory biomarkers related to asthma exacerbation in children but not child and caregiver report of airway symptomatology.

Characterization of the L-Arginine/Nitric Oxide Pathway and Oxidative Stress in Pediatric Patients with Atopic Diseases

Introduction: L-Arginine (Arg) is a semi-essential amino acid. Constitutive and inducible nitric oxide synthase (NOS) isoforms convert Arg to nitric oxide (NO), a potent vaso- and bronchodilator with multiple biological functions. Atopic dermatitis (AD) and bronchial asthma (BA) are atopic diseases affecting many children globally. Several studies analyzed NO in airways, yet the systemic synthesis of NO in AD and BA in children with BA, AD or both is elusive. Methods: In a multicenter study, blood and urine were obtained from 130 of 302 participating children for the measurement of metabolites of the Arg/NO pathway (BA 31.5%; AD 5.4%; AD + BA 36.1%; attention deficit hyperactivity disorder (ADHD) 12.3%). In plasma and urine amino acids Arg and homoarginine (hArg), both substrates of NOS, asymmetric dimethylarginine (ADMA) and symmetric dimethylarginine (SDMA), both inhibitors of NOS, dimethylamine (DMA), and nitrite and nitrate, were measured by gas chromatography–mass spectrometry. Malondialdehyde (MDA) was measured in plasma and urine samples to evaluate possible effects of oxidative stress. Results: There were no differences in the Arg/NO pathway between the groups of children with different atopic diseases. In comparison to children with ADHD, children with AD, BA or AD and BA had higher plasma nitrite (p < 0.001) and nitrate (p < 0.001) concentrations, suggesting higher systemic NO synthesis in AD and BA. Urinary excretion of DMA was also higher (p = 0.028) in AD and BA compared to patients with ADHD, suggesting elevated ADMA metabolization. Discussion/Conclusion: The Arg/NO pathway is activated in atopic diseases independent of severity. Systemic NO synthesis is increased in children with an atopic disease. Plasma and urinary MDA levels did not differ between the groups, suggesting no effect of oxidative stress on the Arg/NO pathway in atopic diseases.

Early age exposure to moisture and mould is related to FeNO at the age of 6 years

BACKGROUND

Exposure to indoor moisture damage and visible mold has been found to be associated with asthma and respiratory symptoms in several questionnaire-based studies by self-report. We aimed to define the prospective association between the early life exposure to residential moisture damage or mold and fractional exhaled nitric oxide (FeNO) and lung function parameters as objective markers for airway inflammation and asthma in 6-year-old children.

METHODS

Home inspections were performed in children's homes when infants were on average 5 months old. At age 6 years, data on FeNO (n = 322) as well as lung function (n = 216) measurements were collected. Logistic regression and generalized additive models were used for statistical analyses.

RESULTS

Early age major moisture damage and moisture damage or mold in the child's main living areas were significantly associated with increased FeNO levels (>75th percentile) at the age of 6 years (adjusted odds ratios, 95% confidence intervals, aOR (95% CI): 3.10 (1.35-7.07) and 3.16 (1.43-6.98), respectively. Effects were more pronounced in those who did not change residential address throughout the study period. For lung function, major structural damage within the whole home was associated with reduced FEV1 and FVC, but not with FEV1/FVC. No association with lung function was observed with early moisture damage or mold in the child's main living areas.

CONCLUSION

These results underline the importance of prevention and remediation efforts of moisture and mold-damaged buildings in order to avoid harmful effects within the vulnerable phase of the infants and children's immunologic development.

Nasal nitric oxide in relation to asthma characteristics in a longitudinal asthma cohort study

OBJECTIVE

Cross-sectional studies report relations between low nasal nitric oxide (nNO) and poor asthma control and between low nNO and chronic rhinosinusitis (CRS). In our cohort study, we studied if changes in nNO related to changes in asthma control, symptoms of CRS, or asthma or rhinitis medication.

METHODS

A total of 196 subjects with predominantly mild to moderate asthma, aged 10-35 years, performed nNO measurements at both baseline and follow-up after a median of 43 (range 23-65) months. Asthma control, CRS symptoms, and medication, were questionnaire-assessed at both timepoints. IgE sensitisation against aeroallergens was quantified at baseline.

RESULTS

There was an increase in nNO between baseline and follow-up (764 ± 269 ppb vs. 855 ± 288 ppb, p < 0.001). When adjusted for covariates, a larger increase in nNO was found in subjects sensitised to perennial aeroallergens than those not sensitised (92 (16-167) ppb), as well as in subjects with daily use of inhaled corticosteroids (ICS) at baseline but not at follow-up than those on ICS daily at both timepoints (146 (51-242) ppb). In the same model, subjects using nasal steroids daily at both timepoints had decreased nNO compared with those without such treatment at both timepoints (-185 (-321-(-48)) ppb). No relations between changes in nNO levels and changes in asthma control or symptoms of CRS were found.

CONCLUSION

Longitudinal changes in nNO were not related to changes in asthma control, but were related to changes in asthma or rhinitis medication.

The Value of FENO Measurement for Predicting Treatment Response in Patients with Acute Exacerbation of Chronic Obstructive Pulmonary Disease

Background

Fractional exhaled nitric oxide (FENO) has been shown to be a marker of airway inflammation in various pulmonary diseases, including chronic obstructive pulmonary disease (COPD). In this study, we assessed the FENO level in patients with acute exacerbations of COPD (AECOPD) and analyzed the predictive value of the FENO level for treatment response.

Methods

Demographic data were collected at admission. FENO, lung function, blood gases, COPD Assessment Test (CAT), and modified Medical Research Council (mMRC) scores were measured at admission and on day 7. At the second visit, the patients were asked to report their health status; scores ranged from 1 to 5, representing "much better", "slightly better", "no change", "slightly worse", and "much worse", respectively. The treatment response was evaluated based on the patient's reported health status (responders were those who reported much better and slightly better) and lung function (responders were those who presented an increase in FEV1 over 200 mL).

Results

A total of 182 patients were recruited into the analysis. The FENO level positively correlated with an increase in FEV1 and FEV1% (r = 0.291, p < 0.001 and r = 0.205, p = 0.005, respectively), but negatively correlated with a decrease in the COPD Assessment Test (CAT) score (r = -0.197, p = 0.008) and patient-reported health status (rho = -0.408, p<0.001). An inverse correlation was observed between FENO concentrations at admission and the length of hospital stay. The cut-off point for differentiating responders, identified by health status, was 18 ppb, with the sensitivity being 89.7% and specificity 88.9%.

Conclusion

FENO levels, determined at hospital admission, are potential to predict the overall treatment response in AECOPD patients, including remission in subjective patient-reported health statuses and, also, improvements in lung function.

Registry Number

ChiCTR-ROC-16,009,087 (http://www.chictr.org.cn/).

Value of bronchial reversibility to salbutamol, exhaled nitric oxide and responsiveness to methacholine to corroborate the diagnosis of asthma in children

INTRODUCTION AND OBJECTIVES

Functional and inflammatory measures have been recommended to corroborate asthma diagnosis in schoolchildren, but the evidence in this regard is conflicting. We aimed to determine, in real-life clinical situation, the value of spirometry, spirometric bronchial reversibility to salbutamol (BDR), bronchial responsiveness to methacholine (MCT) and fractional exhaled nitric oxide (FENO), to corroborate the diagnosis of asthma in children on regular inhaled corticosteroids (ICS) referred from primary care.

METHODS

One hundred and seventy-seven schoolchildren with mild-moderate persistent asthma, on treatment with regular ICS, participated in the study. Abnormal tests were defined as FENO ≥ 27 ppb, BDR (FEV1 ≥ 12%) and methacholine PC20 ≤ 4 mg/mL.

RESULTS

The proportions of positive BDR, FENO and MCT, were 16.4%, 33.3%, and 87.0%, respectively. MCT was associated with FENO (p < 0.03) and BDR (p = 0.001); FENO was associated with BDR (p = 0.045), family history of asthma (p = 0.003) and use of asthma medication in the first two years of life (p = 0.004). BDR was significantly related with passive tobacco exposure (p = 0.003).

CONCLUSIONS

Spirometry, BDR and BDR had a poor performance for corroborating diagnosis in our asthmatic children on ICS treatment; on the contrary, MCT was positive in most of them, which agrees with previous reports. Although asthma tests are useful to corroborate asthma when positive, clinical diagnosis remains the best current approach for asthma diagnosis, at least while better objective and feasible measurements at the daily practice are available. At present, these tests may have a better role for assessing the management and progression of the condition.

Association between family management and asthma control in children with asthma

PURPOSE

The purpose of this study is to investigate the association between family management and asthma control in children with asthma.

DESIGN AND METHODS

This cross-sectional descriptive study recruited 142 children with asthma and their parents. We used the Family Management Measure (FaMM), the Childhood Asthma Control Test (C-ACT), and fractional exhaled nitric oxide (FeNO) detectors to assess family management and asthma control. The McNemar's test was used to determine the proportional difference between C-ACT and FeNO in evaluating asthma control. Pearson correlation analysis and multiple linear regression analysis were used to assess the relationship between family management and asthma control in children with asthma.

RESULTS

There was no significant difference in the proportion of C-ACT and FeNO in evaluating asthma control (McNemar's test p = .593). Child's Daily Life, Condition Management Ability, and Parental Mutuality were positively correlated with C-ACT (r = 0.398 to 0.655; all p < .05) and negatively correlated with FeNO (r = -0.245 to -0.402; all p < .05); Condition Management Effort, Family Life Difficulty, and View of Condition Impact were negatively correlated with C-ACT (r = -0.416 to -0.672; all p < .05) and positively with FeNO (r = 0.248 to 0.427; all p < 0.05). Child's Daily Life, Condition Management Effort, and View of Condition Impact dimensions significantly predicted the C-ACT results, and the Condition Management Effort and View of Condition Impact dimensions significantly predicted the FeNO results (p < .05).

PRACTICAL IMPLICATIONS

Pediatric nurses could provide family management education for parents to improve asthma control in children. In addition, pediatric nurses might assess asthma control condition of asthmatic children in combination with C-ACT and FeNO levels.

Inhibitors of nitric oxide synthase can reduce extracellular traps from neutrophils in asthmatic children in vitro

AIM

This study aimed to explore the link between neutrophil extracellular traps (NETs) and childhood asthma, to investigate the ability of nitric oxide (NO) to induce NETs in asthmatic children and find inhibitors to reduce NETs in the NO synthesis pathway.

METHODS

A total of 49 children with mild persistent asthma were included in the study and 20 healthy children's blood samples were collected as healthy controls. Children with asthma were divided into symptomatic and asymptomatic groups according to the presence or absence of symptoms on the day of blood collection. Neutrophils in peripheral blood were isolated and plasma was preserved. NO donor (sodium nitroferricyanide(III) dehydrate [SNP]) could provide NO and proved by a fluorescent probe. A PicoGreen Kit was used to detect the NETs quantificationally. Fluorescence microscopy prepared to observe the main structures of NETs. We measured NETs components (extracellular free double-stranded DNA [dsDNA]) in healthy, symptomatic and asymptomatic groups' plasma samples, and we compared the ability of SNP with phosphate-buffered saline, lipopolysaccharides (LPS), and phorbol 12-myristate 13-acetate (PMA) to induce NETs. NO synthase (NOS) inhibitors were added to see the impact on NETs formation.

RESULTS

Plasma was obtained from all blood samples of 69 children. The neutrophils of 40 asthmatic and 20 healthy children were successfully obtained, the recovery rate was over 95%, and the cell activity was over 80%. There was higher extracellular free dsDNA in the plasma of symptomatic group (n = 27) than asymptomatic group (n = 22) and healthy group (n = 20; P < .05). Studies on neutrophils from 40 children with asthma found that NO can be produced by adding SNP, PMA, and LPS. SNP could induce NETs with dose- and time-dependent. PMA (160 nM) had the strongest ability to induce NETs, LPS (200 ng/mL) followed, SNP (200 µM) was the weakest (P < .05), and the amount of NETs in the asthma group was significantly higher than that in the healthy group (P < .05). NOS inhibitors had the same blocking capacity for PMA- and LPS-induced NETs (P > .05), while NG-nitro- l-arginine methyl ester (500 µM) had the strongest inhibitory effect on SNP induction with time-dependent (P < .05). Inducible NOS was found in the NETs structure.

CONCLUSION

Children with asthma had higher levels of NETs in peripheral blood, especially when they had asthma symptoms. We verified the ability of NO to induce NETs, and found neutrophils from asthmatic children can produce more NETs in vitro. NOS inhibitors blocked this process may provide new therapeutic targets for childhood asthma.

Serum Levels of Epithelial-Derived Cytokines as Interleukin-25 and Thymic Stromal Lymphopoietin after a Single Dose of Mepolizumab in Patients with Severe Non-Allergic Eosinophilic Asthma: A Short Report

The bronchial epithelium has continuous contact with environmental agents initiating and maintaining airway type 2 inflammation in asthma. However, there is a lack of data on whether reduced airway eosinophilic inflammation can affect the production of epithelial-derived mediators, such as interleukin-25 (IL-25) and thymic stromal lymphopoietin (TSLP). The aim of this study was to investigate the changes in serum levels of IL-25 and TSLP after a single dose of mepolizumab, a humanized monoclonal antibody to interleukin-5 (IL-5), in patients with severe non-allergic eosinophilic asthma (SNEA). We examined 9 SNEA patients before and four weeks after administration of 100 mg mepolizumab subcutaneously. The fractional exhaled nitric oxide (FeNO) level was analysed using an electrochemical assay (NIOX VERO®, Circassia, UK). Serum IL-25 and TSLP levels were measured by ELISA. Four weeks after the single dose of mepolizumab, blood eosinophil count significantly decreased from 0.55 ± 0.20 × 109/l to 0.14 ± 0.04 × 109/l (p = 0.01) and FEV1 increased from 2.1 ± 0.5 l (65.4 ± 8.8% of predicted) to 2.6 ± 0.4 l (76.4 ± 9.1% of predicted) (p = 0.04), while FeNO level has not changed (32.3 ± 8.4 vs 42.9 ± 12.6 ppb). Serum IL-25 level significantly decreased from 48.0 ± 17.2 pg/mL to 34.8 ± 17.1 pg/mL (p = 0.02) with same tendency in TSLP level: from 359.8 ± 71.3 pg/mL to 275.6 ± 47.8 pg/mL (p = 0.02). It has also been noticed a significant relation between changes in the blood eosinophil count and serum IL-25 level (r = 0.81, p = 0.008), as well as between changes in serum IL-25 and TSLP levels (r = 0.93, p = 0.004) after a single dose of mepolizumab. Thus, anti-IL-5 treatment with mepolizumab might diminish the production of bronchial epithelial-derived cytokines IL-25 and TSLP in patients with SNEA which is potentially related to reduced eosinophilic inflammation. This trial is registered in ClinicalTrial.gov with identifier NCT03388359.

Tai Chi Chuan Exercise Improves Lung Function and Asthma Control through Immune Regulation in Childhood Asthma

Background

Tai Chi Chuan (TCC) is an exercise of low to moderate intensity with key features of mindfulness, structural alignment, and flexibility to relax the body and mind in adults. Our previous study showed that TCC could improve the quality of life (QoL), pulmonary function, and fractional exhaled nitric oxide in asthmatic children. We further investigated whether the benefits induced by TCC were associated with immune regulation.

Method

Six- to twelve-year-old children diagnosed with mild to severe persistent asthma for at least one year according to the Global Initiative for Asthma guidelines were enrolled from a tertiary pediatric allergy center in Taiwan. Asthmatic children were divided into two groups based on their choice: (1) the TCC group had a 60-minute TCC exercise session once weekly led by an instructor and (2) the control group kept their original activity levels. All other exercises were encouraged as usual. Pulmonary function tests, laboratory tests, standardized pediatric asthma QoL questionnaire (PAQLQ(S)), and childhood asthma control test (C-ACT) were performed before and after the TCC program (12 weeks). Data on medications and exacerbations were collected from medical records.

Results

There were no differences between the TCC (n = 25) and control (n = 15) groups at baseline, except that the C-ACT showed significantly lower results in the TCC group (p=0.045). After 12 weeks, the number of leukocytes (p=0.041) and eosinophils (p=0.022) decreased, while regulatory T cells increased significantly (p=0.008) only in the TCC group. Lung functions (FEV₁ and PEFR) were significantly improved in both the TCC (p < 0.001) and control (p=0.045 and 0.019, respectively) groups, while the PAQLQ(S) and C-ACT (p < 0.001) showed improvement only in the TCC group. Moreover, compared to the control group, the exacerbations within 12 weeks after the study were significantly decreased in the TCC group (p=0.031). After multiple regression by a conditional forward method, the factors that were significantly associated with exacerbation within 12 weeks after study is the practice of TCC and exacerbation within 24 weeks before study (p=0.013 and 0.015, respectively) after adjusting for age, sex, asthma severity, PEF, FEV₁, C-ACT, PAQLQ(S), and medication score at baseline.

Conclusion

TCC exercise may improve pulmonary functions, asthma control, and QoL and prevent exacerbations in asthmatic children through immune regulation. Further research on detailed mechanisms is mandated.

Exhaled nitric oxide can't replace the methacholine challenge in suspected pediatric asthma

BACKGROUND

In adults, measurement of F_ENO has been recently suggested as a substitute for the methacholine challenge test (MCT) for diagnosis of asthma. This study aimed to evaluate whether FeNO is a substitute for MCH also in children with suspicious asthma.

METHODS

During a single visit steroid naive children (5-17 years) with suspicious asthma underwent skin prick test (SPT), F_ENO measurement and spirometry prior and during MCT (one concentration procedure). Results of the SPT (atopy/non-atopy) and MCT (asthma/non-asthma) were used for categorization. ROC analysis in atopy non-atopy subgroups yielded sensitivity, specificity, positive and negative predictive value (PPV and NPV) for F_ENO.

RESULTS

The SPT revealed atopy in 134 out of 222 children (age 9.7 ± 3.2 years) investigated and asthma was diagnosed in 114 (77/37 atopy/non-atopy) patients. F_ENO values in patients with atopic asthma were significantly higher compared to those with either non-atopic asthma or atopia without asthma (18 ppb (5-89) vs 7 ppb (5-36); p < 0.001; 18 ppb (5-89) vs 11 ppb (5-98); p < 0.05). Sensitivity and specificity of F_ENO for diagnosing atopic asthma (F_ENO≥15.5 ppb; AUC = 0.635, p < 0.01) were 61.1% and 64.9% and non-atopic asthma (F_ENO≥ 6.5 ppb; AUC = 0.445, p = 0.382) 54.1% and 39.2%, respectively. The PPV/NPV for F_ENO were 0.70/0.55 in atopy and 0.39/0.54 in non-atopy patients, respectively.

CONCLUSION

In children, F_ENO is not appropriate to substitute for the MCT. However, in patients with a negative SPT a F_ENO in the normal range makes the presence of atopic asthma unlikely.

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.

Severe asthma in children: Evaluation and management

Severe asthma in children is associated with significant morbidity. Children with severe asthma are at increased risk for adverse outcomes including medication-related side effects, life-threatening exacerbations, and impaired quality of life. It is important to differentiate between severe therapy resistant asthma and difficult-to-treat asthma due to comorbidities. The most common problems that need to be excluded before a diagnosis of severe asthma can be made are poor medication adherence, poor medication technique or incorrect diagnosis of asthma. Difficult to treat asthma is a much more common reason for persistent symptoms and exacerbations and can be managed if comorbidities are clearly addressed. Children with persistent symptoms and exacerbations despite correct inhaler technique and good medical adherence to standard Step 4 asthma therapies according to the guidelines^1,2, should be referred to an asthma specialist with expertise in severe asthma.

Asthma in Children: A Brief Review for Primary Care Providers

Pediatric asthma is a common chronic condition with wide-ranging implications for children's health, their families, and the health care system. The diagnosis may be relatively straightforward for the child with characteristic symptoms, triggers, and response to therapy, but there are other less common presentations that can make the diagnosis challenging. Diagnosing asthma in a toddler with recurrent wheezing can be particularly difficult. Treating asthma in a step-wise fashion usually reduces symptom frequency and improves asthma control. Asthma exacerbations and poor outcomes from acute exacerbations remain an area in which we have room for improvement. This article provides an overview of the diagnosis and management of childhood asthma for the primary care provider. [Pediatr Ann. 2019;48(3):e103-e109.].

Approaches to Asthma Diagnosis in Children and Adults

Although the hallmark features of asthma include reversible airflow obstruction, airway eosinophilia, and symptoms of recurrent wheeze associated with breathlessness and cough, it is a heterogeneous disease. The extent of the pathophysiological abnormalities are variable between patients. Despite this, until recently, asthma diagnosis had been made very simplistically predominantly from a clinical history and examination, and often a trial of medication such as short acting bronchodilators. The limitations of this approach have become increasingly apparent with evidence of inappropriate over diagnosis, under diagnosis and misdiagnosis. Although there is no gold standard single test to make a diagnosis of asthma, there are several objective tests that can be used to support the diagnosis including physiological measures such as obstructive spirometry associated with bronchodilator reversibility and airway hyperresponsiveness. In addition, non-invasive tests of airway inflammation such as exhaled nitric oxide or peripheral blood eosinophils are important to identify those with an allergic or eosinophilic phenotype. Diagnostic guidelines reflect the importance of using objective tests to support a diagnosis of asthma, however practical application in the clinic may not be straightforward. The focus of this review is to discuss the need to undertake objective tests in all patients to support asthma diagnosis and not just rely on clinical features. The advantages, challenges and limitations of performing tests of lung function and airway inflammation in the clinic, the difficulties related to training and interpretation of results will be explored, and the utility and relevance of diagnostic tests will be compared in adults and children.

Estimated individual inhaled dose of fine particles and indicators of lung function: A pilot study among Chinese young adults

Fine particle (PM_2.5)-related lung damage has been reported in most studies regarding environmental or personal PM_2.5 concentrations. To assess effects of personal PM_2.5 exposures on lung function, we recruited 20 postgraduate students and estimated the individual doses of inhaled PM_2.5 based on their microenvironmetal PM_2.5 concentrations, time-activity patterns and refereed inhalation rates. During the period of seven consecutive days in each of the four seasons, we repeatedly measured the daily lung function parameters and airway inflammation makers such as fractional exhaled nitric oxide (FeNO) as well as systemic inflammation markers including interleukin-1β on the final day. The high individual dose (median (IQR)) of inhaled PM_2.5 was 957 (948) μg/day. We observed a maximum FeNO increase (9.1% (95%CI: 2.2-15.5)) at lag 0 day, a maximum decrease of maximum voluntary ventilation (11.8% (95% CI: 4.6-19.0)) at lag 5 day and a maximum interleukin-1β increase (103% (95% CI: 47-159)) at lag 2 day for an interquartile range increase in the individual dose of inhaled PM_2.5 during the four seasons. Short-term exposure to PM_2.5 assessed by the individual dose of inhaled PM_2.5 was associated with higher airway and systemic inflammation and reduced lung function. Further studies are needed to understand better underlying mechanisms of lung damage following acute exposure to PM_2.5.