Measurements of fractional exhaled nitric oxide in pediatric asthma

Assessing Asthma Control by Impulse Oscillometry and Fractional Expiratory Nitric Oxide in Children With Normal Spirometry

BACKGROUND

Because spirometric parameters fail to address current status of asthma in some patients, additional tests are required for better evaluation of asthma.

OBJECTIVE

We aimed to test the ability of impulse oscillometry (IOS) and fractional expiratory nitric oxide (FeNO) in identifying inadequately controlled asthma (ICA) that was not uncovered by spirometry.

METHODS

Recruited asthmatic children between ages of 8 and 16 years underwent spirometry, IOS, and FeNO measurements on the same day. Only subjects who had spirometric indices within normal range were included. Asthma Control Questionnaire-6 scores of 0.75 or lower and greater than 0.75 indicated well-controlled asthma (WCA) and ICA. Percent predicted values of IOS parameters and IOS reference values for upper and lower limits of normal (>95th and <5th percentiles, respectively) were calculated on the basis of previously published equations.

RESULTS

There were no significant differences in all spirometric indices between the WCA (n = 59) and the ICA (n = 101) groups. The % predicted values of IOS parameters except resistance at 20 Hz (R20) were significantly different between the 2 groups. Receiver operating characteristic analysis showed that the highest and lowest areas under the curve were 0.81 and 0.67 for the difference between the resistances at 5 Hz and 20 Hz (R5-R20) and R20 in discrimination of ICA versus WCA. The areas under the curve for IOS parameters were improved by combination with FeNO. The better discriminative ability of IOS was also supported by the higher values of the concordance index for the resistance at 5 Hz (R5), R5-R20, the reactance at 5 Hz (X5), and the resonant frequency of reactance than those for spirometric parameters. Compared with those with normal values, subjects with abnormal IOS parameters or high FeNO had significantly higher odds of having ICA.

CONCLUSIONS

The IOS parameters and FeNO were shown to be useful in identifying children with ICA when spirometry was normal.

Developing Fractional Exhaled Nitric Oxide Predicted and Upper Limit of Normal Values for a Disadvantaged Population

BACKGROUND

Fractional exhaled nitric oxide (Feno), used as a biomarker, is influenced by several factors including ethnicity. Normative data are essential for interpretation, and currently single cutoff values are used in children and adults.

RESEARCH QUESTION

Accounting for factors that influence Feno, (1) what are appropriate predicted and upper limit of normal (ULN) Feno values in an underserved population (First Nations Australians), (2) how do these values compare with age-based interpretive guidelines, and (3) what factors influence Feno and what is the size of the effect?

STUDY DESIGN AND METHODS

Feno data of First Nations Australians (age < 16 years, n = 862; age ≥ 16 years, n = 348) were obtained. Medical history using participant questionnaires and medical records were used to define healthy participants. Flexible regression using spline functions, as used by the Global Lung Function Initiative, were used to generate predicted and ULN values.

RESULTS

Look-up tables for predicted and ULN values using age (4-76 years) and height (100-200 cm) were generated and are supplied with a calculator for clinician use. In healthy First Nations children (age < 18 years), ULN values ranged between 25 and 60 parts per billion (ppb) when considering only biologically plausible age and height combinations. For healthy adults, ULN values ranged between 39 and 88 ppb. Neither the current Feno interpretation guidelines, nor the currently recommended cutoff of 50 ppb for First Nations children 16 years of age or younger were appropriate for use in this cohort. Our modelling revealed that predicted and ULN values of healthy participants varied nonlinearly with age and height.

INTERPRETATION

Because single pediatric, adult, or all-age Feno cutoff values used by current interpretive guidelines to define abnormality fail to account for factors that modify Feno values, we propose predicted and ULN values for First Nations Australians 4 to 76 years of age. Creating age- and height-adjusted predicted and ULN values could be considered for other ethnicities.

Association of fractional exhaled nitric oxide with asthma morbidity in urban minority children

OBJECTIVE

Fractional exhaled nitric oxide (FeNO) is a well-established measure of allergic airway inflammation and possible useful adjunct disease management tool. We investigated the association of baseline and follow-up FeNO measurements with disease burden in minority children with persistent asthma.

METHODS

A retrospective chart review was conducted on 352 African American and Hispanic children seen at an urban Asthma Center in Bronx, NY. Demographic, clinical characteristics, and pulmonary function tests (PFTs) were compared between children with low, intermediate, and high baseline FeNO levels. Among 95 children with subsequent follow up visits, associations of change in FeNO with demographics, clinical characteristics, and PFTs were examined using mixed effects linear regression models.

RESULTS

A higher proportion of children with intermediate (54%) and high FeNO (58%) levels had lower airways obstruction compared to those with low FeNO levels (33%). Children with intermediate FeNO levels had more annual hospitalizations (2.8 ± 6.2) compared to those with low and high FeNO levels (1.3 ± 2.8 and 1.3 ± 2.5). These associations did not differ between ethnicities. An increase in FeNO over time was associated with higher BMI z-scores (β = 6.2, 95% CI: 1.0 to 11.4) and two or more hospitalizations in the past year (β = 16.1, 95% CI: 1.5 to 30.8).

CONCLUSIONS

Intermediate and high FeNO levels are associated with lower airways obstruction and hospitalizations. Initial and serial FeNO measurements can be a useful adjunctive tool in identifying asthma-related morbidity in urban African American and Hispanic children.

Volatile Organic Compounds as Potential Biomarkers for Noninvasive Disease Detection by Nanosensors: A Comprehensive Review

Biomarkers are biological molecules associated with physiological changes of the body and aids in the detecting the onset of disease in patients. There is an urgent need for self-monitoring and early detection of cardiovascular and other health complications. Several blood-based biomarkers have been well established in diagnosis and monitoring the onset of diseases. However, the detection level of biomarkers in bed-side analysis is difficult and complications arise due to the endothelial dysfunction. Currently single volatile organic compounds (VOCs) based sensors are available for the detection of human diseases and no dedicated nanosensor is available for the elderly. Moreover, accuracy of the sensors based on a single analyte is limited. Hence, breath analysis has received enormous attention in healthcare due to its relatively inexpensive, rapid, and noninvasive methods for detecting diseases. This review gives a detailed analysis of how biomarker imprinted nanosensor can be used as a noninvasive method for detecting VOC to health issues early using exhaled breath analysis.

Determining the Best Tool Comparable with Global Initiative for Asthma Criteria for Assessing Pediatric Asthma Control

Background: Guidelines such as Global Initiative for Asthma (GINA) recommend disease control as the mainstay of asthma management. Objective: To investigate which measure of asthma control best correlates with the GINA criteria for determining asthma control in children. Methods: Child asthma-patients at a tertiary hospital were enrolled in the study after evaluation of response to treatment. Asthma control test (ACT)/pediatric asthma control test (PACT), Pediatric Asthma Quality of Life Questionnaire (PAQLQ), fractional exhaled nitric oxide (FeNO), and lung function parameters were evaluated. Patients were examined by asthma specialists and control status was evaluated based on GINA. Results: The median age (interquartile range) of patients was 10.7 (8.4-12.9) years, 57.9% of patients were boys. Of 228 children, 84.2%, 9.6%, and 6.1% displayed "well-controlled", "partially controlled", and "uncontrolled" asthma, respectively, according to GINA. The patients with "partially controlled" and "uncontrolled" asthma were grouped as "not well-controlled." The cutoff levels were 22, 21, and 5.9 for PACT, ACT, and PAQLQ, respectively, for determining "well-controlled" asthma (P < 0.001). With these cutoff values, ACT exhibited higher comparability with GINA than PACT and PAQLQ (κ = 0.473, 0.221, and 0.150, respectively, P < 0.001). PAQLQ had higher agreement with GINA criteria in children ≥12 years old (κ = 0.326, P < 0.001 and κ = 0.151, P = 0.014, respectively). Correctly classified patients with PACT, ACT, and PALQLQ based on GINA with these cutoff levels were 93 (64.1%), 63 (75.9%), and 139 (62.9%), respectively. FeNO and lung function parameters were unsuccessful at revealing control status according to GINA. Conclusion: ACT is better than PACT for comparability with GINA. Better correlation of PAQLQ and ACT and better comparability of PAQLQ and GINA were evident in older children.

Evaluation of Fractional Exhaled Nitric Oxide in Pediatric Asthma and Allergic Rhinitis

Fractional exhaled nitric oxide (FeNO) is a non-invasive test for evaluating the degree of airway inflammation and for the diagnosis, evaluation, and treatment of asthma. We attempted to measure FeNO levels in Korean children with asthma and determine its cutoff value for diagnosing asthma. We enrolled 176 children and adolescents between the ages of 5 and 18 years, who visited for the evaluation of chronic cough, shortness of breath, and wheezing. Among them, 138 patients who underwent skin prick tests or inhalation Immuno CAP (UniCAP; Pharmacia, Uppsala, Sweden) tests for allergy testing together with a pulmonary function test were included. FeNO was measured using a NIOX MINO (Aerocrine AB, Solna, Sweden) instrument according to the American Thoracic Society/European Respiratory Society (ATS/ERS) guidelines. There were 29 patients with asthma, 43 with rhinitis, and 38 with asthma and allergic rhinitis. In the asthma group, FeNO levels significantly correlated with total immunoglobulin E (r = 0.572, p < 0.001), but did not show significant correlation with pulmonary function test parameters (forced vital capacity—FVC, forced expiratory volume in one second—FEV1, FEV1/FVC) or PC20 (provocative concentration of methacholine causing a 20% fall in FEV1). The FeNO cutoff values obtained in the asthma and asthma rhinitis groups were 16.5 ppb and 18.5 ppb, respectively. Hence, we provide a FeNO cutoff value according to the presence or absence of rhinitis in pediatric patients with asthma.

Fractional Exhaled Nitric Oxide Values in Indigenous Australians 3 to 16 Years of Age

BACKGROUND

Fractional exhaled nitric oxide (Feno) levels can identify eosinophilic asthma phenotypes. We aimed to determine Feno values of healthy Aboriginal and/or Torres Strait Islander (Indigenous) Australians, differences between these Indigenous ethnic groups, and appropriateness of published cutoff values.

METHODS

We measured Feno levels in 1,036 Indigenous Australians (3-16 years of age). Participants were classified into healthy (ie, no asthma or atopy history) or asthmatic and/or atopic groups.

RESULTS

Median Feno values and distribution did not differ between Indigenous ethnicities. For healthy participants < 12 years of age (n = 390), 7.2% of our cohort fell into the inflammatory zone of the American Thoracic Society (ATS), National Institute for Health and Care Excellence (NICE), and British Thoracic Society (BTS)/Scottish Intercollegiate Guidelines Network (SIGN) guidelines (cutoff 35 parts per billion [ppb]), but only 3.8% fell into this category when using the Global Initiative for Asthma (GINA) guidelines (50 ppb). Similarly, when using the NICE and BTS/SIGN guidelines (40 ppb) for participants 12 to 16 years of age (n = 213), more healthy participants fell into the inflammatory zone compared with the ATS and GINA guidelines (50 ppb) (9.9% vs 4.7%, respectively).

CONCLUSIONS

Feno values for healthy Indigenous Australians children (3-16 years of age) are likely higher than published white-based values. The GINA recommended cutoff value (> 50 ppb) appears the most appropriate for identifying healthy Indigenous children but requires confirmation from a larger study.

[Application of pulmonary function and fractional exhaled nitric oxide tests in the standardized management of bronchial asthma in children]

OBJECTIVE

To investigate the changes of pulmonary function and fractional exhaled nitric oxide (FeNO) in the standardized treatment of bronchial asthma in children.

METHODS

A total of 254 children who were newly diagnosed with acute exacerbation of bronchial asthma were selected as asthma group, and they were divided into two subgroups: asthma with concurrent rhinitis and asthma without concurrent rhinitis. All patients received the standardized management and treatment for one year. The pulmonary function parameters included forced expiratory volume in one second (FEV1), peak expiratory flow (PEF), maximal mid-expiratory flow (MMEF), and mid-expiratory flow at 25%, 50%, and 75% of vital capacity (MEF25, MEF50, and MEF75). The FeNO levels were measured before treatment and at 3, 6, 9, and 12 months after treatment. Another 62 healthy children were selected as the control group, and the pulmonary function and FeNO levels were measured only once.

RESULTS

During one year of standardized treatment, FEV1, PEF, MMEF, MEF25, MEF50, and MEF75 gradually increased, and FeNO levels gradually decreased (P<0.05). Indicators of large airway function, such as FEV1 and PEF, almost returned to normal after 6 months of treatment; indicators of small airway function, such as MMEF, MEF25, MEF50, and MEF75 almost returned to normal after 9 months of treatment; there were no significant differences in the above indices between the asthma group and the control group after one year of treatment (P>0.05). However, the asthma group had a significantly higher FeNO levels than the control group after one year of treatment (P<0.05). The asthmatic patients with concurrent rhinitis had significantly higher FeNO levels than those without concurrent rhinitis before treatment and 3 months after treatment (P<0.05). Before treatment, there was a significant negative correlation between FeNO levels and pulmonary function parameters (P<0.05).

CONCLUSIONS

With the standardized treatment of bronchial asthma in children, pulmonary function parameters gradually increase and FeNO levels gradually decrease. The recovery of large airway function occurs earlier than the recovery of small airway function. Furthermore, the effect of rhinitis on airway responsiveness should be noted.

[Application of pulmonary function and fractional exhaled nitric oxide tests in the standardized management of bronchial asthma in children]

OBJECTIVE

To investigate the changes of pulmonary function and fractional exhaled nitric oxide (FeNO) in the standardized treatment of bronchial asthma in children.

METHODS

A total of 254 children who were newly diagnosed with acute exacerbation of bronchial asthma were selected as asthma group, and they were divided into two subgroups: asthma with concurrent rhinitis and asthma without concurrent rhinitis. All patients received the standardized management and treatment for one year. The pulmonary function parameters included forced expiratory volume in one second (FEV1), peak expiratory flow (PEF), maximal mid-expiratory flow (MMEF), and mid-expiratory flow at 25%, 50%, and 75% of vital capacity (MEF25, MEF50, and MEF75). The FeNO levels were measured before treatment and at 3, 6, 9, and 12 months after treatment. Another 62 healthy children were selected as the control group, and the pulmonary function and FeNO levels were measured only once.

RESULTS

During one year of standardized treatment, FEV1, PEF, MMEF, MEF25, MEF50, and MEF75 gradually increased, and FeNO levels gradually decreased (P<0.05). Indicators of large airway function, such as FEV1 and PEF, almost returned to normal after 6 months of treatment; indicators of small airway function, such as MMEF, MEF25, MEF50, and MEF75 almost returned to normal after 9 months of treatment; there were no significant differences in the above indices between the asthma group and the control group after one year of treatment (P>0.05). However, the asthma group had a significantly higher FeNO levels than the control group after one year of treatment (P<0.05). The asthmatic patients with concurrent rhinitis had significantly higher FeNO levels than those without concurrent rhinitis before treatment and 3 months after treatment (P<0.05). Before treatment, there was a significant negative correlation between FeNO levels and pulmonary function parameters (P<0.05).

CONCLUSIONS

With the standardized treatment of bronchial asthma in children, pulmonary function parameters gradually increase and FeNO levels gradually decrease. The recovery of large airway function occurs earlier than the recovery of small airway function. Furthermore, the effect of rhinitis on airway responsiveness should be noted.

Does Ethnicity Influence Fractional Exhaled Nitric Oxide in Healthy Individuals?: A Systematic Review

BACKGROUND

Fractional exhaled nitric oxide (Feno) is used clinically as a biomarker of eosinophilic airway inflammation. Awareness of the factors influencing Feno values is important for valid clinical interpretation.

METHODS

We undertook a systematic review of PubMed, Cochrane Library, Scopus, and Web of Science databases and reference lists of included articles to evaluate whether ethnicity influences Feno values, and to determine if this influence affects clinical interpretation according to current guidelines. We included all studies that performed online Feno measurements on at least 25 healthy, non-Caucasian individuals, and examined the effect of ethnicity on Feno.

RESULTS

From 62 potential studies, 12 studies were included. One study recruited only children (< 12 years of age), six studies recruited children and/or adolescents, four studies recruited adults only, and a single study involved children, adolescents, and adults. In total, 16 different ethnic populations representing 11 ethnicities were studied. Ethnicity was considered a significant influencing factor in 10 of the included studies. We found the geometric mean Feno to be above the normal healthy range in two studies. We also identified five studies in which at least 5% of participants had Feno results above the age-specific inflammatory ranges.

CONCLUSIONS

Ethnicity influences Feno values, and for some ethnic groups this influence likely affects clinical interpretation according to current guidelines. There is a need to establish healthy Feno reference ranges for specific ethnic groups to improve clinical application.

Association of wheezing phenotypes with fractional exhaled nitric oxide in children

Asthma comprises a heterogeneous group of disorders characterized by airway inflammation, airway obstruction, and airway hyperresponsiveness (AHR). Airway inflammation, which induces AHR and recurrence of asthma, is the main pathophysiology of asthma. The fractional exhaled nitric oxide (FeNO) level is a noninvasive, reproducible measurement of eosinophilic airway inflammation that is easy to perform in young children. As airway inflammation precedes asthma attacks and airway obstruction, elevated FeNO levels may be useful as predictive markers for risk of recurrence of asthma. This review discusses FeNO measurements among early-childhood wheezing phenotypes that have been identified in large-scale longitudinal studies. These wheezing phenotypes are classified into three to six categories based on the onset and persistence of wheezing from birth to later childhood. Each phenotype has characteristic findings for atopic sensitization, lung function, AHR, or FeNO. For example, in one birth cohort study, children with asthma and persistent wheezing at 7 years had higher FeNO levels at 4 years compared to children without wheezing, which suggested that FeNO could be a predictive marker for later development of asthma. Preschool-aged children with recurrent wheezing and stringent asthma predictive indices also had higher FeNO levels in the first 4 years of life compared to children with wheezing and loose indices or children with no wheeze, suggesting that FeNO measurements may provide an additional parameter for predicting persistent wheezing in preschool children. Additional large-scale longitudinal studies are required to establish cutoff levels for FeNO as a risk factor for persistent asthma.