The utility of sputum eosinophils and exhaled nitric oxide for monitoring asthma control with special attention to childhood asthma

Endotyping Chronic Respiratory Diseases: T2 Inflammation in the United Airways Model

Over the past 15 years, the paradigm of viewing the upper and lower airways as a unified system has progressively shifted the approach to chronic respiratory diseases (CRDs). As the global prevalence of CRDs continues to increase, it becomes evident that acknowledging the presence of airway pathology as an integrated entity could profoundly impact healthcare resource allocation and guide the implementation of pharmacological and rehabilitation strategies. In the era of precision medicine, endotyping has emerged as another novel approach to CRDs, whereby pathologies are categorized into distinct subtypes based on specific molecular mechanisms. This has contributed to the growing acknowledgment of a group of conditions that, in both the upper and lower airways, share a common type 2 (T2) inflammatory signature. These diverse pathologies, ranging from allergic rhinitis to severe asthma, frequently coexist and share diagnostic and prognostic biomarkers, as well as therapeutic strategies targeting common molecular pathways. Thus, T2 inflammation may serve as a unifying endotypic trait for the upper and lower airways, reinforcing the practical significance of the united airways model. This review aims to summarize the literature on the role of T2 inflammation in major CRDs, emphasizing the value of common biomarkers and integrated treatment strategies targeting shared molecular mechanisms.

Correlation of induced sputum eosinophil levels with clinical parameters in mild and moderate persistent asthma in children aged 7-18 years

BACKGROUND

Treatment decisions in asthma are currently based on clinical assessment and spirometry. Sputum eosinophil, being a marker of airway inflammation, can serve as a tool for assessing severity and response to treatment in asthma patients.

OBJECTIVES

To measure eosinophil percentage in induced sputum in children with asthma and correlate it with clinical asthma parameters.

METHODS

A prospective observational study was performed at tertiary care hospital on 91 children aged 7-18 years with newly diagnosed mild or moderate persistent asthma. Theinduced sputum eosinophil percentage was obtained at the time of enrollment and three months after treatment with inhaled budesonide. Patients were specifically evaluated for five clinical parameters of asthma, i.e., days of acute exacerbations, use of salbutamol as rescue medication, emergency visits, nighttime cough and days of school absence.

RESULTS

Sputum eosinophil percentage was high (3.1 ± 0.515%) at the time of enrollment which reduced significantly after three months of inhaled budesonide therapy [0.06 ± 0.164% (p < 0.0005)]. Children with moderate persistent asthma had significantly higher values of sputum eosinophil levels than children with mild persistent asthma at the time of enrollment (3.38 ± 0.64% vs. 2.99 ± 0.42%, p  =  0.001) but the difference was not significant after three months of inhaled steroid therapy (0.07 ± 0.18 vs. 0.04 ± 0.12, p  =  0.5104). A significant negative correlation was found between reduction in sputum eosinophil levels and improvement in FEV1 (r = -0.400, p = 0.0001). All the clinical asthma parameters also correlated significantly with the reduction in sputum eosinophil levels after three months of inhaled steroid therapy.

CONCLUSION

Eosinophil levels in induced sputum correlate well with clinical asthma parameters and asthma severity in children. It is a simple, noninvasive and cheap method which can be used for the monitoring of asthma in a resource-limited setting.

The clinician's guide on monitoring children with asthma

Based on a review of the evidence on the usefulness of monitoring disease outcome parameters in childhood asthma and the author's 20-yr clinical experience in managing childhood asthma, this article provides the clinician with up-to-date recommendations on how to monitor childhood asthma in everyday clinical practice. Monitoring should be focused on patient-centered outcomes, such as exacerbations and impact on sports and play. Composite asthma control measures, although reasonably validated, do not take exacerbations into account and have a short recall window, limiting their usefulness as a routine monitoring tool in clinical practice. Lung function, airways hyperresponsiveness, exhaled nitric oxide, and inflammatory markers in sputum are surrogate end points, of little if any interest to patients. There is no evidence to support their use as a monitoring tool in clinical practice; office spirometry may be used as additional information. Rather than monitoring surrogate end points, clinicians should focus on showing a genuine interest in the impact of asthma on children's daily lives, and building and maintaining a partnership by monitoring those characteristics of asthma which have the biggest impact on children (exacerbations and limitations in sports and play), and adjusting treatment accordingly.

Role of exhaled nitric oxide as a predictor of atopy

BACKGROUND

The fractional exhaled nitric oxide (FeNO) is a quantitative, noninvasive and safe measure of airways inflammation that may complement the assessment of asthma. Elevations of FeNO have recently been found to correlate with allergic sensitization. Therefore, FeNO may be a useful predictor of atopy in the general population. We sought to determine the diagnostic accuracy of FeNO in predicting atopy in a population-based study.

METHODS

We conducted a cross-sectional study in an age- and sex- stratified random sample of 13 to 15 year-olds in two communities in Peru. We asked participants about asthma symptoms, environmental exposures and sociodemographics, and underwent spirometry, assessment of FeNO and an allergy skin test. We used multivariable logistic regression to model the odds of atopy as a function of FeNO, and calculated area-under-the-curves (AUC) to determine the diagnostic accuracy of FeNO as a predictor of atopy.

RESULTS

Of 1441 recruited participants, 1119 (83%) completed all evaluations. Mean FeNO was 17.6 ppb (SD=0.6) in atopics and 11.6 ppb (SD=0.8) in non-atopics (p<0.001). In multivariable analyses, a FeNO>20 ppb was associated with an increase in the odds of atopy in non-asthmatics (OR=5.3, 95% CI 3.3 to 8.5) and asthmatics (OR=16.2, 95% CI 3.4 to 77.5). A FeNO>20 ppb was the best predictor for atopy with an AUC of 68% (95% CI 64% to 69%). Stratified by asthma, the AUC was 65% (95% CI 61% to 69%) in non-asthmatics and 82% (95% CI 71% to 91%) in asthmatics.

CONCLUSIONS

FeNO had limited accuracy to identify atopy among the general population; however, it may be a useful indicator of atopic phenotype among asthmatics.

Detecting gene expression in buccal mucosa in subjects with asthma versus subjects without asthma

BACKGROUND

Differences in mRNA expression for inflammatory markers have been observed between subjects with asthma vs. controls and in relation to corticosteroid response. However, these studies utilized methods (e.g., bronchoscopy) that are too invasive to be used routinely in children and in the clinic. The primary purpose of this study was to determine the feasibility of obtaining RNA of adequate quantity and quality from buccal mucosa of children and adults for gene expression studies. Secondly, this study aimed to determine whether gene expression patterns in buccal mucosa are similar to those that have been observed in respiratory epithelium.

METHODS

We enrolled 94 subjects with and without asthma between 5 and 54 years of age. Relative gene expression in buccal mucosa was determined with quantitative RT-PCR for the following genes: CCL2, EDN1, FKBP5, IL8, IFNAR2, NFKB1, RELA, SERPINB2, DENND1B, HRH1, ICAM1, ORMDL3, NR3C1, CLCA1, CRHR1, MUC5B, FCER2, POSTN, GAPDH, PPIA.

RESULTS

mRNA Expression of the following genes was detected in buccal mucosa: CCL2, EDN1, FKBP5, IL8, IFNAR2, NFKB1, RELA, SERPINB2, DENND1B, HRH1, ICAM1, ORMDL3, NR3C1, GAPDH, PPIA. HRH1 was differentially expressed in adults with asthma vs. controls (p = 0.04), and EDN1 was differentially expressed in children with asthma vs. controls 12-18 years old (p = 0.03). A similar trend for HRH1 was observed in children 12-18 years old.

CONCLUSIONS

Buccal mucosa sampling is a reliable method for detecting changes in gene expression in patients with asthma. This non-invasive technique may serve as a valuable tool for diagnosing asthma and evaluating therapeutic response.

Eosinophilic activity and bronchial hyperresponsiveness within an asthmatic paediatric population

BACKGROUND

Our study aims to assess the importance of serum eosinophil cationic protein (ECP) levels as a non-invasive marker of bronchial hyperresponsiveness (BHR) in children with asthma, and may predict objectively the asthmatic severity and sensitivities.

METHODS

This study, which was carried out on 75 asthmatic patients from a paediatric population (average age: nine years old, sex-ratio M/F: 1.64), is based on both interrogation conducted by the clinician and biological explorations, essentially serological testing of ECP and eosinophilia determination, as well as the measurement of serological IgE amounts.

RESULTS

The analysis of the questionnaires and the biological results allowed us to evaluate the clinico-biological relations within this population. ECP, more than eosinophilia, proves to be a relevant marker of asthma severity (p<0.05) and sensitivities within this given population (r=0.65).

CONCLUSION

We were able to show that the evaluation of the serological levels of ECP seems to be a good biological marker of asthma.

Predicting asthma exacerbations in children

PURPOSE OF REVIEW

This review critically assesses recently published literature on predicting asthma exacerbations in children, while also providing general recommendations for future research in this field.

RECENT FINDINGS

Current evidence suggests that every effort should be made to provide optimal treatment to achieve adequate asthma control, as this will significantly reduce the risk of severe disease exacerbations. Children who have had at least one asthma exacerbation in the previous year are at highest risk for subsequent exacerbations, regardless of disease severity and/or control. Although several tools and biomarkers to predict asthma exacerbations have been recently developed, these approaches need further validation and/or have only had partial success in identifying children at risk.

SUMMARY

Although considerable progress has been made, much remains to be done. Future studies should clearly differentiate severe asthma exacerbations due to inadequate asthma control from those occurring in children whose asthma is well controlled, utilize standardized definitions of asthma exacerbations, and use a systematic approach to identify the best predictors after accounting for the multiple dimensions of the problem. Our ability to correctly predict the development of severe asthma exacerbations in an individual child should improve in parallel with increased knowledge and/or understanding of the complex interactions among genetic, environmental (e.g. viral infections) and lifestyle (e.g. adherence to treatment) factors underlying these events.

Urinary bromotyrosine measures asthma control and predicts asthma exacerbations in children

OBJECTIVES

To determine the usefulness of urinary bromotyrosine, a noninvasive marker of eosinophil-catalyzed protein oxidation, in tracking with indexes of asthma control and in predicting future asthma exacerbations in children.

STUDY DESIGN

Children with asthma were recruited consecutively at the time of clinic visit. Urine was obtained, along with spirometry, exhaled nitric oxide, and Asthma Control Questionnaire data. Follow-up phone calls were made 6 weeks after enrollment.

RESULTS

Fifty-seven participants were enrolled. Urinary bromotyrosine levels tracked significantly with indexes of asthma control as assessed by Asthma Control Questionnaire scores at baseline (R = 0.38, P = .004) and follow-up (R = 0.39, P = .008). Participants with high baseline levels of bromotyrosine were 18.1-fold (95% CI 2.1-153.1, P = .0004) more likely to have inadequately controlled asthma and 4.0-fold more likely (95% CI 1.1-14.7, P = .03) to have an asthma exacerbation (unexpected emergency department visit; doctor's appointment or phone call; oral or parenteral corticosteroid burst; acute asthma-related respiratory symptoms) over the ensuing 6 weeks. Exhaled nitric oxide levels did not track with Asthma Control Questionnaire data; and immunoglobulin E, eosinophil count, spirometry, and exhaled nitric oxide levels failed to predict asthma exacerbations.

CONCLUSIONS

Urinary bromotyrosine tracks with asthma control and predicts the risk of future asthma exacerbations in children.

What's new in asthma pathophysiology and immunopathology?

Research on asthma pathophysiology over the past decade has expanded the complex repertoire involved in the pathophysiology of asthma to include inflammatory, immune and structural cells, as well as a wide range of mediators. Studies have identified a role for connective and other mesenchymal tissues involved in airway remodeling. Recent findings have implicated the innate immune response in asthma and have revealed interesting patterns of interaction between the innate and adaptive immune response and the associated complex chronic inflammatory reaction. New immune cell populations have also been added to this repertoire, including Tregs, natural killer T cells and Th17 cells. The role of the eosinophil, a prominent pathological feature in most asthma phenotypes, has also been expanding to include roles such as tissue modifiers and immune regulators via a number of fascinating and hitherto unexplored mechanistic pathways. In addition, new and significant roles have been proposed for airway smooth muscle cells, fibroblasts, epithelial and endothelial cells. Tissue remodeling is now considered an integral element of asthma pathophysiology. Finally, an intricate network of mediators, released from both immune and inflammatory cells, including thymus stromal lymphopoietin and matrix metalloproteinases, have added to the complex milieu of asthma immunity and inflammation. These findings have implications for therapy and the search for novel strategies towards better disease management. Sadly, and perhaps due to the complex nature of asthma, advances in therapeutic discoveries and developments have been limited. Thus, understanding the precise roles played by the numerous dramatis personae in this odyssey, both individually and collectively within the context of asthma pathophysiology, continues to pose new challenges. It is clear that the next stage in this saga is to embark on studies that transcend reductionist approaches to involve system analysis of the complex and multiple variables involved in asthma, including the need to narrow down the phenotypes of this condition based on careful analysis of the organs (lung and airways), cells, mediators and other factors involved in bronchial asthma.

The prevalence and meaning of eosinophilia in renal diseases on a nephrology consultation service

BACKGROUND

In recent years, we have come to understand that the eosinophil is more than the end point in clearance of parasitic infection or a maladaptive response to asthma and allergic reactions. Since eosinophilia has been reported to be common in renal diseases, we thought that an evaluation of the associations of eosinophilia on a renal consultation service would add some value to the understanding of their role in renal disease.

METHODS

This was a prospective cross-sectional study of 1339 consecutive patients referred to the nephrology service after hospitalization who were evaluated for the relationship of the amount of serum eosinophils to their diagnosis, gender, age and the presence of autoimmune disease, cancer, infection, liver disease, pleural effusions, allergies and use of prednisone, beta-blockers or beta agonists, in addition to the total white blood count, urine protein, serum concentration creatinine and phosphorus levels and estimated glomerular filtration rate.

RESULTS

The presence of vascular disease correlated the most strongly with increased eosinophil count (partial correlation coefficient, r = 0.18, P = 0.006), followed by pleural effusions (r = 0.17, P = 0.001), while total white cell count (r = -0.18, P = 0.008) and administration of beta-blockers (r = -0.13, P = 0.047) demonstrated significant inverse correlations and the presence of autoimmune disease, cancer, allergies, proteinuria and serum phosphorus concentration demonstrated no significant correlation.

CONCLUSION

There are multiple associations with increased eosinophil counts in patients seen on a nephrology consultant service; however, their presence appears less often in association with allergies or uremia and more often with vascular disease.