What is a clinically meaningful change in exhaled nitric oxide for children with asthma?

Variability in forced expiratory volume in 1 s in children with symptomatically well-controlled asthma

AIMS

Spirometry is used by many clinicians to monitor asthma in children but relatively little is understood about its variability over time. The aim of this study was to determine the variability of forced expiratory volume in 1 s (FEV1) in children with symptomatically well-controlled asthma by applying three different methods of expressing change in FEV1 over 3-month intervals.

METHODS

Data from five longitudinal studies of children with asthma which measured FEV1 at 3-month intervals over 6 or 12 months were used. We analysed paired FEV1 measurements when asthma symptoms were controlled. The variability of FEV1% predicted (FEV1%), FEV1 z-score (FEV1z) and conditional z score for change (Zc) in FEV1 was expressed as limits of agreement.

RESULTS

A total of 881 children had 3338 FEV1 measurements on occasions when asthma was controlled; 5184 pairs of FEV1 measurements made at 3-month intervals were available. Each unit change in FEV1 z score was equivalent to a Zc 1.45 and an absolute change in FEV1% of 11.6%. The limits of agreement for change in FEV1% were -20 and +21, absolute change in FEV1 z were -1.7 and +1.7 and Zc were -2.6 and +2.1. Regression to the mean and increased variability in younger children were present for change in FEV1% and FEV1z comparisons, but not Zc.

CONCLUSION

Given the wide limits of agreement of paired FEV1 measurements in symptomatically well-controlled children, asthma treatment should primarily be guided by symptoms and not by a change in spirometry.

Use of exhaled nitric oxide in the diagnosis and monitoring of childhood asthma: myth or maxim?

Asthma is a common condition in children. This review describes the evidence from the literature and international asthma guidelines for using fractional exhaled nitric oxide (FENO) in the diagnosis and monitoring of childhood asthma. The accuracy of FENO measuring devices could be further improved, the difference in FENO results between devices are equivalent to what is considered a clinically important difference. For diagnosing asthma no guideline currently recommends FENO is used as the first test, but many recommend FENO as part of a series of tests. A cut-off of 35 ppb is widely recommended as being supportive of an asthma diagnosis, but evidence from children at risk of asthma suggests that a lower threshold of 25 ppb may be more appropriate. Nine randomised clinical trials including 1885 children have added FENO to usual asthma care and find that exacerbations are reduced when care is guided by FENO (OR for exacerbation compared to usual care 0.77, 95% CI 0.62-0.94). What is not clear is what cut-off(s) of FENO should be used to trigger a change in treatment. After 30 years of intensive research there is not sufficient evidence to recommend FENO for routine diagnosing and monitoring asthma in children.

Educational aims

To give the reader an overview of literature that supports and does not support the role of FENO in diagnosing asthma in children.To give the reader an overview of literature that supports and does not support the role of FENO in monitoring asthma in children.To give the reader an understanding of the role of FENO in international guidelines for diagnosing and monitoring asthma in children.

Cough and cough hypersensitivity as treatable traits of asthma

Cough is a common and troublesome symptom in people with asthma and is often associated with poorer asthma control and exacerbations. Apart from asthma, other causes or comorbidities might underlie cough in asthma, such as rhinosinusitis and bronchiectasis. Eosinophilic inflammation and bronchoconstriction can lead to an acute episode of cough or worsen chronic cough. Cough hypersensitivity with laryngeal paraesthesia, allotussia, and hypertussia might underlie the cough of asthma through augmented sensory nerve excitability of upper-airway vagal sensory nerves. Cough associated with bronchoconstriction and type 2 inflammation should respond to inhaled corticosteroids and long-acting β-adrenoceptor agonist therapy. For cough hypersensitivity in adults, speech and language therapy and neuromodulators (eg, gabapentin) could be considered. In children, there is no consistent association of asthma with cough sensitivity or between cough and asthma severity. Further research is needed to realise the potential of cough as a measure of asthma control, to understand the mechanisms of cough in asthma, and to develop safe, effective treatments and a precision-medicine approach to the management of cough in asthma in children and adults.

Reducing asthma attacks in children using exhaled nitric oxide (RAACENO) as a biomarker to inform treatment strategy: a multicentre, parallel, randomised, controlled, phase 3 trial

BACKGROUND

The benefit of fractional exhaled nitric oxide (FeNO) in guiding asthma treatment is uncertain. We evaluated the efficacy of adding FeNO to symptom-guided treatment in children with asthma versus only symptom-guided treatment.

METHODS

RAACENO was a multicentre, parallel, randomised, controlled, phase 3 trial done in 35 secondary care centres and 17 primary care recruitment sites (only seven primary care sites managed to recruit patients) in the UK. Patients with a confirmed asthma diagnosis, aged 6-15 years, prescribed inhaled corticosteroids, and who received a course of oral corticosteroids for at least one asthma exacerbation during the 12 months before recruitment were included. Participants were randomly assigned to either FeNO plus symptom-guided treatment (intervention) or symptom-guided treatment alone (standard care) using a 24 h in-house, web-based randomisation system. Participants and the clinical and research teams were not masked to the group allocation. A web-based algorithm gave treatment recommendations based on the Asthma Control Test (ACT) or Childhood ACT (CACT) score; current asthma treatment; adherence to study treatment in the past 3 months; and use of FeNO (in the intervention group). Follow-up occurred at 3-month intervals for 12 months. The primary outcome was any asthma exacerbation treated with oral corticosteroids in the 12 months after randomisation, assessed in the intention-to-treat population. This study is registered with the International Standard Randomised Controlled Trial Registry, ISRCTN67875351.

FINDINGS

Between June 22, 2017, and Aug 8, 2019, 535 children were assessed for eligibility, 20 were ineligible and six were excluded post-randomisation. 509 children were recruited and at baseline, the mean age of participants was 10·1 years (SD 2·6), and 308 (60·5%) were male. The median FeNO was 21 ppb (IQR 10-48), mean predicted FEV₁ was 89·6% (SD 18·0), and median daily dose of inhaled corticosteroids was 400 μg budesonide equivalent (IQR 400-1000). Asthma was partly or fully controlled in 256 (50·3%) of 509 participants. The primary outcome, which was available for 506 (99%) of 509 participants, occurred in 123 (48·2%) of 255 participants in the intervention group and 129 (51·4%) of 251 in the standard care group, the intention-to-treat adjusted odds ratio (OR) was 0·88 (95% CI 0·61 to 1·27; p=0·49). The adjusted difference in the percentage of participants who received the intervention in whom the primary outcome occurred compared with those who received standard care was -3·1% (-11·9% to 5·6%). In 377 (21·3%) of 1771 assessments, the algorithm recommendation was not followed. Adverse events were reported by 27 (5·3%) of 509 participants (15 in the standard care group and 12 in the intervention group). The most common adverse event was itch after skin prick testing (reported by eight participants in each group).

INTERPRETATION

We found that the addition of FeNO to symptom-guided asthma treatment did not lead to reduced exacerbations among children prone to asthma exacerbation. Asthma symptoms remain the only tool for guiding treatment decisions.

FUNDING

National Institute for Health Research.

Does lung function change in the months after an asthma exacerbation in children?

BACKGROUND

There are limited data describing lung function changes in children after an asthma exacerbation. Our hypothesis was that lung function does not fully recover in children in the months following an asthma exacerbation.

METHODS

We used a data set of children with asthma where lung function (including FEV₁ , FEV₁ /FVC ratio and FEF_25-75 ) was measured at 3-month intervals over a year. Mixed-level models compared spirometry measured on two occasions 3 months apart before a single exacerbation (assessments 1 and 2) with measurements made on two occasions after the exacerbation (assessments 3 and 4), with adjustment for covariates. Changes in spirometry over a year were also analysed across those with exacerbations in no, one or more than one 3-month periods.

RESULTS

For the 113 children who had a single exacerbation, spirometry measured at assessments 1 or 2 did not differ from measurements at assessments 3 or 4 when the whole population was considered. When stratified into tertiles by change in %FEV₁ between assessments 2 and 3, those with the greater reduction were more likely to be treated with long-acting beta-agonist, but in this category, %FEV₁ at assessment 4 had returned to the value at assessment 1. %FEV₁ did not change over a 12-month period within and between the three exacerbation categories (n = 809).

CONCLUSION

One or more asthma exacerbation was not associated with a fall in lung function for the whole population. In a subset of individuals, lung function does fall after an exacerbation but returns to pre-exacerbation values after a period of months.

Pediatric Pulmonology 2020 year in review: Asthma

Pediatric asthma is a heterogeneous and common chronic condition with significant morbidity and burden on the healthcare system. Despite advances in the field, the disease has proven to be increasingly complex to diagnose and management strategies are constantly evolving. Studies from 2020 have advanced the field even further, particularly with regard to new methods of diagnosis and monitoring, treatment of severe asthma, modifiable risk factors like exercise and obesity, aerosol delivery, and viral respiratory infections contributing to the development of asthma. Continued studies are needed to improve our care for children with asthma and we look forward to future advances. This article is part of our 2020 "Year in Review" series, in which we summarize publications in major topic areas, in the context of selected literature from other journals relevant to our discipline.