The utility of exhaled nitric oxide in patients with suspected asthma

Diagnostic accuracy of FeNO in asthma and predictive value for inhaled corticosteroid responsiveness: A prospective, multicentre study

BACKGROUND

Fractional exhaled nitric oxide (FeNO) is promising for diagnosing asthma and could replace bronchial provocation (BP). To date, cut-off values have been derived by post hoc analysis only. The aim was to validate the diagnostic accuracy for predefined FeNO cut-off values and the predictive value for responsiveness to inhaled corticosteroids (ICS).

METHODS

We conducted a prospective, diagnostic, multicentre study with patients attending three private practices of pneumologists in Upper Bavaria, Germany, from July 3, 2020 to Jan 21, 2022. Index test was FENO measurement. Reference standard was Tiffeneau ratio (FEV₁/VC) or airway resistance as assessed by whole body plethysmography, with additional BP or bronchodilation test. Follow-up was performed after 12 weeks. Analyses of Receiver Operating Characteristics curves were conducted to determine the diagnostic accuracy and predictive value of FeNO.

FINDINGS

308 patients with complete follow-up were recruited, 186 (60·4%) were female, average age was 44·7 years, 161 (52·3%) had asthma. Regarding diagnostic accuracy, the area under the curve (AUC) was 0·718 (95% CI 0·661-0·775; p < 0·001). Sensitivity at FeNO >50 ppb was 0·24 (95% CI 0·18-0·32), specificity 0·99 (0·95-1·0), positive predictive value (PPV) 0·95 (0·84-0·99), negative predictive value (NPV) 0·54 (0·48-0·60). In 66 patients with ´wheezing´ and ´allergic rhinitis´, the sensitivity at FeNO >33 ppb was 0·49 (0·34-0·64), specificity 0·88 (0·64-0·99), PPV 0·92 (0·75-0·99), NPV 0·38 (0·23-0·54). In 68 patients with ICS medication, responsiveness was predicted at the cut-off >43 ppb, with a sensitivity of 0·55 (95%CI 0·36-0·74), specificity 0·82 (0·66-0·92), PPV 0·70 (0·47-0·87), NPV 0·71 (0·56-0·84).

INTERPRETATION

FeNO measurement allows a valid ruling-in of an asthma diagnosis, whereas ruling-out of asthma is not possible. Enhanced probability of ICS responsiveness is also given with increased FeNO values.

FUNDING

Circassia Germany gave 25% discount on the purchase of three NIOX VERO devices.

European Respiratory Society Guidelines for the Diagnosis of Asthma in Adults

Although asthma is very common affecting 5-10% of the population, the diagnosis of asthma in adults remains a challenge in the real world that results in both over- and under-diagnosis. A task force (TF) was set up by the European Respiratory Society to systematically review the literature on the diagnostic accuracy of tests used to diagnose asthma in adult patients and provide recommendation for clinical practice.The TF defined eight PICO (Population, Index, Comparator, and Outcome) questions that were assessed using the GRADE (Grading of Recommendations, Assessment, Development and Evaluation) approach, The TF utilised the outcomes to develop an evidenced-based diagnostic algorithm, with recommendations for a pragmatic guideline for everyday practice that was directed by real-life patient experiences.The TF support the initial use of spirometry followed, and if airway obstruction is present, by bronchodilator reversibility testing. If initial spirometry fails to show obstruction, further tests should be performed in the following order: FeNO, PEF variability or in secondary care, bronchial challenge. We present the thresholds for each test that are compatible with a diagnosis of asthma in the presence of current symptoms.The TF reinforce the priority to undertake spirometry and recognise the value of measuring blood eosinophils and serum IgE to phenotype the patient. Measuring gas trapping by body plethysmography in patients with preserved FEV1/FVC ratio deserves further attention. The TF draw attention on the difficulty of making a correct diagnosis in patients already receiving inhaled corticosteroids, the comorbidities that may obscure the diagnosis, the importance of phenotyping, and the necessity to consider the patient experience in the diagnostic process.

A low exhaled nitric oxide level excludes a short-term benefit from inhaled corticosteroids in suspected asthma: A randomized placebo-controlled trial

BACKGROUND AND OBJECTIVE

Fractional exhaled nitric oxide (FeNO) is a non-invasive biomarker that reflects IL-4/IL-13 production and therefore represents T2 allergic inflammation. FeNO has previously been used to guide inhaled corticosteroid (ICS) treatment in asthma. The purpose of this study was to determine if a low FeNO (≤27 ppb) could be used to reliably identify patients with symptoms suggestive of asthma who would not benefit from initiating treatment with an ICS.

METHODS

A total of 180 steroid-naïve adults with healthcare professional suspected asthma and an FeNO of ≤27 ppb were randomized to receive either 400 mcg of budesonide or placebo daily for 3 months. The primary outcome was the difference in the Asthma Control Questionnaire 7 (ACQ7) between treatment groups and the study was powered to determine equivalence. Secondary outcomes were the difference in FEV₁ , Medical Research Council and Leicester Cough Questionnaire scores.

RESULTS

One hundred and thirty-four patients (68 budesonide and 66 placebo) completed the study and were included in the analysis. The between-group mean difference in ACQ7 from baseline to the end of the study was -0.25 and the 95% CI around this difference was -0.004 to 0.495 confirming equivalence (p < 0.05). Differences in forced expiratory volume over 1 s and other secondary outcomes were also small and clinically unimportant.

CONCLUSION

The results of this study suggest that steroid-naïve patients with symptoms suggestive of asthma and an FeNO ≤ 27 ppb are unlikely to benefit from initiating treatment with an ICS over 3 months. However, further research is recommended to confirm these findings before withholding ICS treatment.

Evaluation of the diagnostic accuracy of fractional exhaled nitric oxide (FeNO) in patients with suspected asthma: study protocol for a prospective diagnostic study

INTRODUCTION

The measurement of fractional exhaled nitric oxide (FeNO) is promising for diagnosing asthma and might substitute for bronchial provocation (BP) tests. To evaluate the diagnostic accuracy of FeNO within a confirmatory study, the following hypotheses will be tested: (1) A FeNO cut-off >50 ppb (parts per billion) is suitable for diagnosing asthma (sensitivity 35%, specificity 95%); (2) If the clinical symptoms 'allergic rhinitis' and 'wheezing' are present, asthma can be diagnosed at FeNO >33 ppb with a positive predictive value (PPV) >70% and (3) A FeNO >33 ppb can predict responsiveness to inhaled corticosteroid (ICS) with a PPV >70%.

METHODS AND ANALYSIS

A prospective diagnostic study will be conducted in three practices of pneumologists in Germany. 300 patients suspected of suffering from asthma will be included. As an index test, patients perform FeNO measurement with the device NIOX VERO. As reference a test, patients are examined with whole bodyplethysmography and BP, if necessary. After 3 months, patients with an asthma diagnosis will be examined again to verify the diagnosis and evaluate ICS responsiveness. Patients who did not receive an asthma diagnosis at the initial examination will be phoned after 3 months and asked about persistent respiratory symptoms to exclude false negative findings. As a primary target, sensitivity and specificity of FeNO >50 ppb will be determined. As a secondary target the PPV for asthma at FeNO >33 ppb, when the symptoms 'allergic rhinitis' and 'wheezing' are present, will be calculated. Regarding ICS responsiveness, the PPV of FeNO >33 ppb will be determined.

ETHICS AND DISSEMINATION

The study was approved by the Ethical Committee of the Technical University of Munich (Reference number 122/20 S). The major results will be published in peer-reviewed academic journals and disseminated through conferences.

TRIAL REGISTRATION NUMBER

DRKS00021125.

Fractional exhaled nitric oxide and asthma treatment adherence

PURPOSE OF REVIEW

Despite increased clinician awareness, nonadherence to inhaled corticosteroid treatment presents a major challenge to successful asthma management and risks inappropriate treatment escalation, particularly in severe disease. In patients with Type-2 mediated biology, fractional exhaled nitric oxide (FeNO) has a role in assessment and monitoring of adherence to inhaled corticosteroids.

RECENT FINDINGS

Asthmatic patients with elevated FeNO are at an increased risk of exacerbation. High FeNO is often secondary to suboptimal adherence to inhaled corticosteroid treatment, whether intentional or nonintentional. FENO-suppression can 'unmask' underlying adherence issues and is a useful test in the presence of Type-2 biology in the 'difficult-to-control' asthma population. Identification of nonadherence can improve asthma control and prevent inappropriate commencement of costly biologic therapies.

SUMMARY

Assessment of adherence and FeNO response to monitored inhaled corticosteroid in Type-2 biomarker high asthmatic individuals may prevent unnecessary escalation to biologic therapy. Establishing an 'optimised' FeNO may alert clinicians to the possibility of underlying nonadherence at future clinical assessments.

Clinical utility of fractional exhaled nitric oxide in severe asthma management

Asthma is a chronic inflammatory disease of the airways, affecting over 350 million people worldwide and placing a significant burden on healthcare providers and wider society. Approximately 5-10% of asthma patients are diagnosed with severe asthma and typically are associated with increased risk of hospitalisation from exacerbations, increased morbidity, mortality and higher asthma-associated healthcare costs. Nitric oxide (NO) is an important regulator of immune responses and is a product of inflammation in the airways that is over-produced in asthma. Fractional exhaled NO (F _eNO) is predominantly used as a predictor of response to inhaled corticosteroids (ICSs), to monitor adherence and as a diagnostic tool in ICS-naïve patients. In the UK, the National Institute for Health and Care Excellence (NICE) guidelines recommend the use of F _eNO for the initial diagnosis of patients with suspected asthma. In the USA, American Thoracic Society (ATS) guidelines recommend F _eNO as part of the initial diagnosis of asthma and for monitoring of airway inflammation. F _eNO has also been shown to be a predictive factor for asthma exacerbations, with higher levels being associated with a greater number of exacerbations. In addition, higher levels of F _eNO have been shown to be associated with a decline in lung function. F _eNO testing is a cost-effective procedure and has been shown to improve patient management when combined with standard assessment methods. Recent evidence suggests that F _eNO may also be useful as a surrogate biomarker for the assessment and management of severe asthma and to predict responsiveness to some biological therapies.

Inhaled Corticosteroid Therapy in Adult Asthma. Time for a New Therapeutic Dose Terminology

The Global Initiative for Asthma guidelines use the traditional terminology of "low," "medium," and "high" doses of inhaled corticosteroids (ICS) to define daily maintenance doses of 100 to 250 μg, >250 to 500 μg, and >500 μg, respectively, of fluticasone propionate or equivalent for adults with asthma. This concise clinical review proposes that this terminology is not evidence based and that prescribing practice based on this terminology may lead to the use of inappropriately excessive doses of ICS. Specifically, the ICS dose that achieves 80-90% of the maximum obtainable benefit is currently classified as a low dose, with the description of two higher dose levels of medium and high, which are associated with significant risk of systemic adverse effects. Asthma guidelines and clinician prescribing practice need to be modified in accordance with the currently available evidence of the dose-response relationship of ICS in adult asthma. We propose a reclassification of ICS doses based on a "standard daily dose," which is defined as 200-250 μg of fluticasone propionate or equivalent, representing the dose at which approximately 80-90% of the maximum achievable therapeutic benefit of ICS is obtained in adult asthma across the spectrum of severity. It is recommended that ICS treatment be started at these standard doses, which then represent the doses at which maintenance ICS are prescribed at step 2 and within ICS/long-acting β-agonist combination therapy at step 3. The opportunity is available to prescribe higher doses within ICS/long-acting β-agonist maintenance therapy in accordance with the stepwise approach to asthma treatment at step 4.

Severe T2-high asthma in the biologics era: European experts' opinion

The European Respiratory Biologics Forum gathered participants from 21 countries in Madrid, Spain, to discuss the management and treatment of severe asthma in the era of biologics. The current insights on the pathophysiology of severe asthma were discussed, as well as the role of respiratory biologics in clinical practice and strategies for eliminating chronic use of oral corticosteroids. The participants also highlighted the key challenges in identifying patients with severe asthma based on phenotypes, biomarkers and treatable traits, and the existing problems in patient referral to specialist care. The monitoring of treatment was debated and the need for a change towards precision medicine and personalised care was emphasised throughout the meeting. This review provides a summary of the discussions and highlights important concerns identified by the participants regarding the current management of severe asthma.

Treatable traits of chronic airways disease

PURPOSE OF REVIEW

To describe the rationale on which the treatable traits approach to the management of airways disease is based and the issues that need to be considered for its implementation in clinical practice.

RECENT FINDINGS

In clinical practice, treatable traits can be classified according to both endotypes and phenotypes, broadly grouped within pulmonary, extrapulmonary, environmental and behavioural factors. Specific investigations and treatments are undertaken for each of the traits rather than a 'one size fits all' stepwise approach to pharmacological treatment which currently represents the core of asthma and chronic obstructive pulmonary disease (COPD) guidelines. Although there is strong evidence of the benefit of the treatable traits approach to specific traits in asthma and/or COPD, there is uncertainty regarding the preferred method of implementation, efficacy and cost-effectiveness of multidimensional intervention programmes in clinical practice. It is likely that 'master protocols' for randomized controlled trials will be required to evaluate such multiple interventions in broad populations of patients with airways disease.

SUMMARY

Current evidence suggests that the precision medicine approach based on the identification and treatment of treatable traits is preferable to a 'one-size-fits-all' stepwise approach to the treatment of airways disease, although high-quality evidence to guide the practical application of this multidimensional management strategy is now required. VIDEO ABSTRACT.

Type 2 Biomarkers and Prediction of Future Exacerbations and Lung Function Decline in Adult Asthma

BACKGROUND

Type 2 biomarkers that predict both likelihood of future severe exacerbations and response to mAb therapy in asthma would be useful clinically in identifying patients both at greater risk of hospitalization and most likely to benefit from mAb therapy.

OBJECTIVE

To describe the association between type 2 biomarkers, blood eosinophils, fractional exhaled nitric oxide (Feno), serum periostin, and serum IgE, and time to severe exacerbation in a broad asthma population.

METHODS

Participants from 2 adult asthma cohorts with baseline measurements of blood eosinophils, Feno, serum periostin, and serum IgE were reviewed after at least 12 months to obtain an exacerbation history, corroborated with general practitioner and hospital medical records. The association between baseline type 2 biomarkers and time to exacerbation was described by Cox proportional hazard ratios (HRs) using multivariate models.

RESULTS

A total of 212 participants were followed for a median (range) 3.8 (1.1-5.3) years; 67 of 212 (32%) had at least 1 severe exacerbation. The HRs (95% CI) of baseline type 2 biomarkers and time to exacerbation were as follows: blood eosinophils per 0.1 × 10⁹/L increase, 0.89 (0.76-1.05), P = .17; log Feno per 0.693 increase, 0.65 (0.52-0.81), P < .001; log serum periostin per 0.693 increase, 0.62 (0.35-1.09), P = .10; log serum IgE per 0.693 increase, 0.89 (0.80-1.00), P = .05.

CONCLUSIONS

The positive association between type 2 biomarkers and risk of severe exacerbations in populations with severe refractory asthma does not extend to mild and moderate asthma. Non-type 2 asthma may represent a phenotype associated with an increased risk of severe exacerbations in a broad asthma population.

Fractional exhaled nitric oxide as a predictor of response to inhaled corticosteroids in patients with non-specific respiratory symptoms and insignificant bronchodilator reversibility: a randomised controlled trial

BACKGROUND

Chronic non-specific respiratory symptoms are difficult to manage. This trial aimed to evaluate the association between baseline fractional exhaled nitric oxide (FeNO) and the response to inhaled corticosteroids in patients with non-specific respiratory symptoms.

METHODS

In this double-blind randomised placebo-controlled trial, we enrolled undiagnosed patients, aged 18-80 years, with cough, wheeze, or dyspnoea and less than 20% bronchodilator reversibility across 26 primary care centres and hospitals in the UK and Singapore. Patients were assessed for 2 weeks before being randomly assigned (1:1) to 4 weeks of treatment with extrafine inhaled corticosteroids (QVAR 80 μg, two puffs twice per day, equivalent to 800 μg per day beclomethasone dipropionate) or placebo. Randomisation was stratified by baseline FeNO measurement: normal (≤25 parts per billion [ppb]), intermediate (>25 tp <40 ppb), and high (≥40 ppb). The primary endpoint was change in Asthma Control Questionnaire (ACQ7) mean score. We used generalised linear modelling to assess FeNO as a predictor of response, estimating an interaction effect between FeNO and treatment on change in ACQ7. We did our primary and secondary analyses in the per-protocol set, which excluded patients with non-completion of the primary endpoint, non-compliance to treatment (ascertained by patient report), and study visits made outside the predefined visit windows. This study is registered on ClinicalTrials.gov, number NCT02294279.

FINDINGS

Between Feb 4, 2015, and July 12, 2016, we randomly assigned 294 patients to extrafine inhaled corticosteroid treatment (n=148) or placebo (n=146). Following exclusions due to protocol violations, we analysed 214 patients (114 extrafine inhaled corticosteroids and 100 placebo). We observed a significant interaction between baseline FeNO and treatment group for every 10 ppb increase in baseline FeNO, with the change in ACQ7 greater in the extrafine inhaled corticosteroids group than in the placebo group (difference between groups 0·071, 95% CI 0·002 to 0·139; p=0·044). The most common adverse events were nasopharyngitis (18 [12%] patients in the treatment group vs 13 [9%] in the placebo group), infections and infestations (25 [17%] vs 21 [14%]), and respiratory, thoracic, and mediastinal disorders (13 [9%] vs 17 [12%]).

INTERPRETATION

FeNO measurement is an easy and non-invasive tool to use in clinical practice in patients with non-specific respiratory symptoms to predict response to inhaled corticosteroids. Further research is needed to examine its role in patients with evidence of other airway diseases, such as chronic obstructive pulmonary disease.

FUNDING

Sponsored by OPRI with partial funding by Circassia and study drugs provided by TEVA.

A novel statistical model for analyzing data of a systematic review generates optimal cutoff values for fractional exhaled nitric oxide for asthma diagnosis

OBJECTIVES

Measurement of fractional exhaled nitric oxide (FE_NO) might substitute bronchial provocation for diagnosing asthma. However, optimal FE_NO thresholds for diagnosing asthma remain unclear. We reanalyzed data collected for a systematic review investigating the diagnostic accuracy of FE_NO measurement to exploit all available thresholds under consideration of pretest probabilities using a newly developed statistical model.

STUDY DESIGN AND SETTING

One hundred and fifty data sets for a total of 53 different cutoffs extracted from 26 studies with 4,518 participants were analyzed with the multiple thresholds model. This model allows identifying thresholds at which the test is likely to perform best.

RESULTS

Diagnosing asthma might only be possible in a meaningful manner when the pretest probability of asthma is at least 30%. In that case, FE_NO > 50 ppb leads to a positive predictive value of 0.76 [95% confidence interval (CI): 0.29-0.96]. Excluding asthma might only be possible, when the pretest probability of asthma is 30% at maximum. Then, FE_NO < 20 ppb leads to a negative predictive value of 0.86 (95% CI 0.66-0.95).

CONCLUSION

The multiple thresholds model generates a more comprehensive and more clinically useful picture of the effects of different thresholds, which facilitates the determination of optimal thresholds for diagnosing or excluding asthma with FE_NO measurement.

Severe asthma in children

Most children with asthma have their disease easily controlled if low-dose inhaled corticosteroids (ICSs) are regularly and correctly administered. If a child presents with asthma which is apparently resistant to therapy with high-dose ICS and other controllers, then they have problematic severe asthma. However, in light of the UK National Review of Asthma Deaths, definitions of severe asthma based solely on the levels of prescribed treatment are too narrow. A detailed assessment of all such children should be performed. First, the diagnosis of asthma should be confirmed, then co-morbidities assessed. Next, a nurse-led assessment further characterizes the problem, conventionally categorizing the child as either having difficult asthma or severe therapy-resistant asthma. Here, we reassess in particular the interactions between, and management of, these two categories, highlighting that this dichotomous classification may need reconsideration. We use bronchoscopy and an intramuscular steroid injection to determine if the child has steroid-resistant asthma, using a novel, multidomain approach because the adult definition does not apply to around half the children we see. Finally, we highlight some mechanistic data which have emerged from this protocol such as the absence of T-helper 2 (TH2) cytokines even in eosinophilic severe asthma and the potential role of the innate epithelial cytokine IL-33, novel data on lineage negative innate lymphoid cells, which we can measure in induced sputum, and demonstrating that intraepithelial neutrophils are associated with better, not worse asthma outcomes. Severe paediatric asthma is very different from severe asthma in adults, and approaches must not be uncritically extrapolated from adult disease to children.

Targeting patients with asthma for omalizumab therapy: choosing the right patient to get the best value for money

The asthma syndrome has many manifestations, termed phenotypes, that arise by specific cellular and molecular mechanisms, termed endotypes. Understanding an individual's asthma phenotype helps clinicians make rational therapeutic decisions while the understanding of endotypes has led to the development of specific precision medications. Allergic asthma is an example of an asthma phenotype and omalizumab, a monoclonal antibody that neutralizes serum immunoglobulin (Ig)E, is a specific targeted treatment which was developed as a result of an understanding of the endotype of allergic asthma. Omalizumab has been widely used in clinical practice in Europe for over a decade as an add-on therapy to treat patients who have severe refractory allergic asthma. Over this period, many centres have reported their experience with omalizumab as an add-on therapy in patients with severe asthma. These 'real world' clinical effectiveness studies have confirmed the benefits, cost-effectiveness and clinical utility of this medication. Combining the outcomes of both sources of research has yielded important insights that may benefit patients with severe asthma, clinicians who treat them, as well as the funding agencies that reimburse the cost of this medication. The purpose of this review is to describe how to identify and evaluate a patient with asthma for whom treatment with omalizumab may be of clinical and cost-effective benefit. The assessment and investigations used to confirm allergic asthma, the objective assessment of adherence to asthma therapy and the expected benefits of add-on omalizumab treatment are described.

Accuracy of FENO for diagnosing asthma: a systematic review

BACKGROUND

Measurement of FE_NO might substitute bronchial provocation for diagnosing asthma. We aimed to investigate the diagnostic accuracy of FE_NO measurement compared with established reference standard.

METHODS

Systematic review and diagnostic meta-analysis. Data sources were Medline, Embase and Scopus up to 29 November 2015. Sensitivity and specificity were estimated using a bivariate model. Additionally, summary receiver-operating characteristic curves were estimated.

RESULTS

26 studies with 4518 participants (median 113) were included. Risk of bias was considered low for six of seven items in five studies and for five items in seven studies. The overall sensitivity in the meta-analysis was 0.65 (95% CI 0.58 to 0.72), the overall specificity 0.82 (0.76 to 0.86), the diagnostic OR 9.23 (6.55 to 13.01) and the area under the curve 0.80 (0.77 to 0.85). In meta-regression analyses, higher cut-off values were associated with increasing specificity (OR 1.46 per 10 ppb increase in cut-off) while there was no association with sensitivity. Sensitivities varied significantly within the different FE_NO devices, but not specificities. Neither prevalence, age, use of bronchoprovocation in >90% of participants or as exclusive reference standard test, nor risk of bias were significantly associated with diagnostic accuracy.

CONCLUSIONS

There appears to be a fair accuracy of FE_NO for making the diagnosis of asthma. The overall specificity was higher than sensitivity, which indicates a higher diagnostic potential for ruling in than for ruling out the diagnosis of asthma.