Predictors of Low and High Exhaled Nitric Oxide Values in Asthma: A Real-World Study

State of the art: Alternative overlap syndrome-asthma and obstructive sleep apnea

In the general population, Bronchial Asthma (BA) and Obstructive Sleep Apnea (OSA) are among the most prevalent chronic respiratory disorders. Significant epidemiologic connections and complex pathogenetic pathways link these disorders via complex interactions at genetic, epigenetic, and environmental levels. The coexistence of BA and OSA in an individual likely represents a distinct syndrome, that is, a collection of clinical manifestations attributable to several mechanisms and pathobiological signatures. To avoid terminological confusion, this association has been named alternative overlap syndrome (vs overlap syndrome represented by the chronic obstructive pulmonary disease-OSA association). This comprehensive review summarizes the complex, often bidirectional links between the constituents of the alternative overlap syndrome. Cross-sectional, population, or clinic-based studies are unlikely to elucidate causality or directionality in these relationships. Even longitudinal epidemiological evaluations in BA cohorts developing over time OSA, or OSA cohorts developing BA during follow-up cannot exclude time factors or causal influence of other known or unknown mediators. As such, a lot of pathophysiological interactions described here have suggestive evidence, biological plausibility, potential or actual directionality. By showcasing existing evidence and current knowledge gaps, the hope is that deliberate, focused, and collaborative efforts in the near-future will be geared toward opportunities to shine light on the unknowns and accelerate discovery in this field of health, clinical care, education, research, and scholarly endeavors.

Exhaled Nitric Oxide as Biomarker of Type 2 Diseases

Nitric oxide (NO) is a short-lived gas molecule which has been studied for its role as a signaling molecule in the vasculature and later, in a broader view, as a cellular messenger in many other biological processes such as immunity and inflammation, cell survival, apoptosis, and aging. Fractional exhaled nitric oxide (FeNO) is a convenient, easy-to-obtain, and non-invasive method for assessing active, mainly Th2-driven, airway inflammation, which is sensitive to treatment with standard anti-inflammatory therapy. Consequently, FeNO serves as a valued tool to aid the diagnosis and monitoring of several asthma phenotypes. More recently, FeNO has been evaluated in several other respiratory and/or immunological conditions, including allergic rhinitis, chronic rhinosinusitis with/without nasal polyps, atopic dermatitis, eosinophilic esophagitis, and food allergy. In this review, we aim to provide an extensive overview of the current state of knowledge about FeNO as a biomarker in type 2 inflammation, outlining past and recent data on the application of its measurement in patients affected by a broad variety of atopic/allergic disorders.

A multicomponent nutraceutical (<i>Perilla frutescens</i>, quercetin, and vitamin D3) as add-on therapy in patients with grass pollen-induced mild persistent asthma and rhinitis

Background Allergic asthma is an inflammatory disease characterized by a type 2 immune response. Pollens are a common cause of seasonal asthma. Allergic rhinitis (AR) frequently associates with asthma. The treatment usually aims at controlling inflammation and relieving symptoms. Inhaled corticosteroids are the most effective controller and short-acting b2-agonists (SABA) as a reliever for asthma. Oral antihistamines and nasal corticosteroids (NC) are the mainstays for AR. A multicomponent nutraceutical containing perilla, quercetin, and vitamin D3 significantly prevented AR exacerbations in children. Thus, the current study explored the add-on use in adult patients with mild persistent asthma and AR due to grass pollen allergy. Methods The treatment lasted three months. Asthma and AR symptoms, asthma control test, spirometry, nasal eosinophils, and use of rescue medications (SABA and NC) were evaluated in the previous grass season and throughout the treatment. All patients were treated with ciclesonide (320 mcg/day) and cetirizine (10 mg/day). Patients were randomly stratified into Group A, taking the nutraceutical, and Group B using the predetermined therapy. Results 90 patients (13-59 years old) were enrolled, and 84 completed the trial. Group A significantly improved all outcomes (p<0.001). Group B did not achieve an improvement in AR symptoms, nasal eosinophils, and nasal steroid use. The intergroup analysis showed that Group A patients experienced less severe bronchial symptoms (- 32 %), AR symptoms (- 39 %), better asthma control (+ 38 %), higher FEV1 (+ 10 %), lower SABA (- 30 %) and NC use (- 41 %), and nasal eosinophils count (- 35 %) than Group B (p<0.0001 for all). No clinically relevant adverse events occurred. Conclusion A multicomponent nutraceutical containing perilla, quercetin, and vitamin D3, as an add-on treatment to inhaled ciclesonide and cetirizine, provided a clinically relevant benefit in patients with mild persistent asthma and AR due to grass pollen uncontrolled by standard therapy.

Exhaled nitric oxide in asthma: from diagnosis to management

PURPOSE OF REVIEW

Exhaled nitric oxide (FENO) is a noninvasive marker of eosinophilic airway inflammation, therefore, highly informative in asthma. Although FENO measurement is a potentially accessible tool to many physicians, recommendations regarding its clinical utility in diagnosing or tailoring treatment have not reached the expected diffusion. More recently FENO emerged as a biomarker for type-2 asthma phenotyping and a predictor of response to biologics.

RECENT FINDINGS

The physiological discoveries and relevant acquisitions in clinical practice regarding FENO in asthma are presented. The FENO story draw a wavy path, characterized by promising findings, exciting confirmations and periods of low visibility. FENO emerged as a tool to increase the probability of asthma diagnosis. FENO predicts response to inhaled glucocorticoids (ICS), favoring the development of tailored treatment strategies and unrevealing nonadherence to ICS in difficult-to-treat or uncontrolled asthma. Finally, FENO was associated with a more severe phenotype and became a consolidated biomarker of type-2 inflammation.

SUMMARY

FENO demonstrated to be a noninvasive and very reproducible test, encompassing many applications in the field of asthma management. Its routinely use, according to international guidelines, may improve the quality of patient assistance, from difficult-to-treat cases to biologic monitoring.

Critical evaluation of asthma biomarkers in clinical practice

The advent of personalized medicine has revolutionized the whole approach to the management of asthma, representing the essential basis for future developments. The cornerstones of personalized medicine are the highest precision in diagnosis, individualized prediction of disease evolution, and patient-tailored treatment. To this aim, enormous efforts have been established to discover biomarkers able to predict patients' phenotypes according to clinical, functional, and bio-humoral traits. Biomarkers are objectively measured characteristics used as indicators of biological or pathogenic processes or clinical responses to specific therapeutic interventions. The diagnosis of type-2 asthma, prediction of response to type-2 targeted treatments, and evaluation of the risk of exacerbation and lung function impairment have been associated with biomarkers detectable either in peripheral blood or in airway samples. The surrogate nature of serum biomarkers, set up to be less invasive than sputum analysis or bronchial biopsies, has shown several limits concerning their clinical applicability. Routinely used biomarkers, like peripheral eosinophilia, total IgE, or exhaled nitric oxide, result, even when combined, to be not completely satisfactory in segregating different type-2 asthma phenotypes, particularly in the context of severe asthma where the choice among different biologics is compelling. Moreover, the type-2 low fraction of patients is not only an orphan of biological treatments but is at risk of being misdiagnosed due to the low negative predictive value of type-2 high biomarkers. Sputum inflammatory cell analysis, considered the highest specific biomarker in discriminating eosinophilic inflammation in asthma, and therefore elected as the gold standard in clinical trials and research models, demonstrated many limits in clinical applicability. Many factors may influence the measure of these biomarkers, such as corticosteroid intake, comorbidities, and environmental exposures or habits. Not least, biomarkers variability over time is a confounding factor leading to wrong clinical choices. In this narrative review, we try to explore many aspects concerning the role of routinely used biomarkers in asthma, applying a critical view over the "state of the art" and contemporarily offering an overview of the most recent evidence in this field.

What is the added value of FeNO as T2 biomarker?

There is increasing evidence about the role of nitric oxide in type 2 (T2) immune response. Fraction of exhaled nitric oxide (FeNO) is a product of airways inflammation and it is increased in patients with asthma. Since Gustaffson published the first article about this biomarker in the 1990s, interest has continued to grow. Compared with other T2 biomarkers such as blood eosinophil count, induced sputum, or serum periostin, FeNO has some remarkable advantages, including its not invasive nature, easy repeatability, and possibility to be performed even in patients with severe airway obstruction. It is considered as an indicator of T2 inflammation and, by the same token, a useful predictor for inhaled steroid response. It is difficult to determine the utility of nitric oxide (NO) for initial asthma diagnosis. In such a heterogenous disease, a single parameter would probably not be enough to provide a complete picture. There is also an important variability among authors concerning FeNO cutoff values and the percentage of sensibility and specificity for diagnosis. Its high specificity indicates a potential role to “rule in” asthma; however, its lower sensibility could suggest a lower capacity to “rule out” this pathology. For this reason, if a diagnosis of asthma is being considered, FeNO should be considered along with other tests. FeNO has also shown its utility to detect response to steroids, adherence to treatment, and risk of exacerbation. Even though there is not enough quality of evidence to establish overall conclusions, FeNO could be an alternative procedure to diagnose or exclude asthma and also a predictive tool in asthma treated with corticosteroids.