Biomarkers to identify sputum eosinophilia in different adult asthma phenotypes

Body Weight and Allergic Asthma: A Narrative Review

Obesity is a known risk factor for asthma development, progression, and exacerbation. Nevertheless, the underlying pathophysiological mechanisms explaining how obesity contributes to the development and progression of asthma have yet to be established. Here, we review human studies examining the associations between asthma and obesity, focusing on the literature from the past 10 years. Overall, current evidence suggests that while both asthma and obesity are complex diseases with significant heterogeneity, they both share various features of chronic inflammation. Furthermore, the interactions between asthma and obesity likely involve allergen-specific T helper type 2 (type 2) immune responses, as well as diverse non-type 2 inflammatory pathways. However, despite considerable progress, studies to date have not definitively elucidated the mechanisms that account for the observed association. A large-scale population-based study combined with translational immunological research, including targeted asthma therapies and pharmacological weight loss therapies, may be required to properly dissect the details of obesity-related asthma pathophysiology.

The role of matrix metalloproteinase-2 and miR-196a2 in bronchial asthma pathogenesis and diagnosis

Background

Bronchial asthma is a persistent inflammatory respiratory condition that restricts the passage of air and causes hyperresponsiveness. Chronic asthma can be classified into three categories: mild, moderate, and severe. Remodeling took place as the extracellular matrix accumulated in the walls of the airways. Inflammation occurs as a result of the damage caused by matrix metalloproteinase-2 (MMP-2) to basement membrane type IV collagen. The severity of asthma may be associated with miR-196a2. The objective of our study was to investigate the underlying mechanisms and clinical relevance of miR-196a2 and MMP-2 serum levels in relation to the severity of asthma.

Methods

This study recruited 85 controls and 95 asthmatics classified as mild, moderate, or severe. Expression of miR-196a2 was measured by quantitative reverse transcriptase PCR. Using the enzyme-linked immunosorbent assay (ELISA), MMP-2, IL-6, and total immunoglobulin E (IgE) levels in the serum of asthmatics of various grades were compared to a control group. MMP-2's diagnostic and prognostic potential was determined using ROC curve analysis. This study also measured blood Eosinophils and PFTs. We examined MMP-2's connections with IgE, blood Eosinophils, and PFTs.

Results

The current investigation found that miR-196a2 expression was significantly higher in the control group than in asthmatic patients as a whole. The study found that severe asthmatics had higher MMP-2, IL-6, and IgE serum levels than healthy controls. We identified the MMP-2 serum concentration cutoff with great sensitivity and specificity. Significant relationships between MMP-2 serum level and miR-196a2 expression in the patient group with severe asthmatics were found. The MMP-2, IL-6, and IgE serum levels were considerably higher in mild, moderate, and severe asthmatics than controls. The miR-196a2 expression and MMP-2 serum concentration correlated positively with IgE and blood eosinophils % and negatively with all lung function tests in the asthmatic patient group.Conclusion: the study revealed that the elevated miR-196a2 expression and serum concentration of MMP-2, IL-6, and IgE associated with elevated blood eosinophils % is associated with pathophysiology and degree of asthma severity. The miR-196a2 expression and MMP-2 serum concentration have a promising diagnostic and prognostic ability in bronchial asthma.

Asthma Inflammatory Phenotypes: How Can We Distinguish Them?

BACKGROUND AND OBJECTIVES

induced sputum is used to assess different inflammatory phenotypes in asthma, but is not used routinely. We aimed to determine the proportion of inflammatory asthma phenotypes based on induced sputum, to find biomarkers that can discriminate between phenotypes, and to evaluate biomarkers in patients with and without biological therapy in different inflammatory asthma phenotypes.

MATERIALS AND METHODS

this cross-sectional study investigated clinical characteristics, asthma control tests, skin prick test, impulse oscillometry (IOS), spirometry, induced sputum, biomarkers (IgE, eosinophils, fractional exhaled nitric oxide (FeNO), serum periostin, IL-5, IL-6, IL-8, IL-17A, IL-33) in 80 asthmatics. A total of 17/80 patients were treated with biologics (10 with omalizumab, 7 with benralizumab).

RESULTS

a total of 31% of patients had eosinophilic asthma (EA), 30% had mixed granulocytic asthma (MGA), 24% had paucigranulocytic asthma (PGA), and 15% had neutrophilic asthma (NA). The difference was found in blood eosinophils (p = 0.002), the highest observed in EA. The cut-off ≥ 240/μL eosinophils, with 64% sensitivity and 72.7% specificity, identified EA (AUC = 0.743, p = 0.001). A higher IL-8 level was associated with NA (p = 0.025). In 63 non-biologic asthma group, eosinophils were higher in EA than in NA, MGA, and PGA (p = 0.012, p = 0.028, and p = 0.049, respectively). A higher IL-17A was associated with EA without biologics (p = 0.004). A significantly higher IL-5 was found in EA treated with biologics, in comparison with EA without biologics (p = 0.043). The number of leucocytes and neutrophils was higher in MGA without biologics (p = 0.049, p = 0.019), while IL-5, IL-6, and IL-8 levels were higher in MGA treated with biologics (p = 0.012, p = 0.032, p = 0.038, respectively).

CONCLUSIONS

EA and MGA were the most prevalent asthma phenotypes. Blood eosinophils can identify EA, both in patients with and without biologics. Apart from the clinical profile, a broad spectrum of biomarkers for assessing inflammatory phenotypes is necessary for an adequate therapy approach to patients with asthma.

Markers of eosinophilic airway inflammation in patients with asthma and allergic rhinitis

Background: Measurement of airway inflammation is an important step to determine phenotype of asthma and allergic rhinitis (AR). Objective: To assess the level of nitric oxide in exhaled air (FeNO), nasal fraction of nitric oxide (nasal NO), their relationship with clinical control and blood eosinophils in patients with steroid-naive mild and moderate asthma and AR. Methods: One hundred forty-seven patients (65 men), ages 26-49.5 years (mean age, 32 years) with AR (n = 81) or AR and concomitant asthma (n = 46) and 20 healthy subjects were included in a single-center cohort study. All the patients underwent spirometry with reversibility test. Control of asthma and AR was assessed by using the Asthma Control Questionnaire and the visual analog scale, respectively. Levels of FeNO and nasal NO were measured by chemiluminescent analyzer, peripheral blood eosinophils were counted by automatic analyzer. Results: The FeNO level was significantly elevated in the patients with asthma and concomitant AR compared with the healthy subjects and was associated with control of both asthma and AR. There was no correlation between nasal NO and control of AR. Receiver operating characteristic analysis revealed that the level of eosinophils of 150 cells/μL may be a cutoff for lower airway eosinophilic inflammation. Blood eosinophils count was unable to distinguish eosinophilic and non-eosinophilic upper airway inflammation. Conclusion: We confirm that FeNO but not nasal NO is a marker of eosinophilic airway inflammation in patients with mild-moderate steroid-naive AR and concomitant asthma. A blood eosinophil level of ≥150 cells/µL may be a simple marker of eosinophilic airway inflammation in patients with asthma. However, its low specificity requires repeated measurements and use in combination with other biomarkers.

Diagnostic accuracy of blood eosinophils in comparison to other common biomarkers for identifying sputum eosinophilia in patients with chronic cough

Background

Sputum eosinophilia is a treatable trait for chronic cough. It is currently not clear whether the blood eosinophil counts could be used to identify sputum eosinophilia in patients with chronic cough. This study aimed to evaluate the diagnostic accuracy of blood eosinophils in comparison to other common type 2 biomarkers for identifying sputum eosinophilia in patients with chronic cough.

Methods

In this prospective study, a total of 658 patients with chronic cough were enrolled. Induced-sputum test, routine blood test, total immunoglobulin E (TIgE), and fractional exhaled nitric oxide (FeNO) level were measured. The percentage of sputum eosinophils (Eos%) ≥ 2.5% was defined as sputum eosinophilia. The area under the curve (AUC) of blood eosinophil counts, TIgE, and FeNO alone or in combination for predicting sputum eosinophilia were analyzed.

Results

The AUC of blood eosinophil counts for predicting sputum eosinophilia in chronic cough patients was moderate [0.826 (0.767-0.885)], as compared to that of FeNO [0.784 (0.720-0.849), P = 0.280] and TIgE [0.686 (0.613-0.760), P = 0.001]. When combining blood eosinophil counts and FeNO for detecting sputum eosinophilia, a significantly larger AUC [0.868 (0.814-0.923), with a sensitivity of 84.2% and a specificity of 82.8%] was yielded, as compared to each single marker alone (all P < 0.05).

Conclusions

Blood eosinophil counts have a moderate diagnostic value for identifying sputum eosinophilia in patients with chronic cough, while a combination of blood eosinophil counts and FeNO measurement can provide additional predictive value.

Association of blood total immunoglobulin E and eosinophils with radiological features of bronchiectasis

BACKGROUND

Our study aimed to investigate whether serum total IgE and blood eosinophils were associated with radiological features of bronchiectasis in a Chinese cohort.

METHODS

We retrospectively enrolled bronchiectasis patients who visited Peking University Third Hospital from Jan 1st, 2012 to Oct 7th, 2021. The clinical, laboratory and chest CT characteristics were analyzed in association with serum total IgE level and blood eosinophil count.

RESULTS

A total of 125 bronchiectasis patients were enrolled, with 50.4% (63/125) female, and a mean age of 62.4 ± 14.1 years. The median serum total IgE level and blood eosinophil count were 47.7 (19.8, 123.0) KU/L and 140 (90, 230) cells/µl, respectively. In patients with a higher than normal (normal range, 0-60 KU/L) total IgE (43.2%, n = 54), more lobes were involved [4 (3, 5) vs. 3 (2, 4), p = 0.008], and mucus plugs were more common (25.9% vs. 9.9%, p =0.017) on HRCT, as compared to those with a normal level of total IgE. The higher IgE group was more likely to have bilateral involvement (p = 0.059), and had numerically higher Smith and Bhalla scores, but the differences were not statistically significant. In patients with an eosinophil count ≥ 150 cells/µl (49.6%, n = 62), the number of lobes involved was greater [4 (3, 5) vs. 3 (2, 4), p = 0.015], and the Smith and Bhalla scores were higher [9 (5, 12) vs. 6 (3, 9), p = 0.009, 7 (5, 11) vs. 5 (3, 9), p = 0.036]. The Smith score was correlated positively with the eosinophil count (r = 0.207, p = 0.020). Fractional exhaled nitric oxide (FeNO) was correlated with total IgE (r = 0.404, p = 0.001) and eosinophil count (r = 0.310, p = 0.014).

CONCLUSIONS

Our study demonstrated that serum total IgE and the blood eosinophil count were associated with the radiological extent and severity of bronchiectasis, necessitating further investigation on the role of T2 inflammation in structural abnormalities of this heterogeneous disease.

Reliability of Total Serum IgE Levels to Define Type 2 High and Low Asthma Phenotypes

Background: High total IgE levels are weak predictors of T2High and have been reported in nonallergic asthma. Therefore, the role of total serum IgE (IgE) in the T2High phenotype is still debated. Objective: This study investigated the reliability of stratifying asthmatics into IgEHigh and IgELow within the T2High and T2Low phenotypes. Methods: This cross-sectional single-center study investigated the association of clinical, functional, and bio-humoral parameters in a large asthmatic population stratified by IgE ≥ 100 kU/L, allergen sensitization, B-EOS ≥ 300/µL, and FENO ≥ 30 ppb. Results: Combining T2 biomarkers and IgE identifies (1) T2Low-IgELow (15.5%); (2) T2Low-IgEHigh (5.1%); (3) T2High-IgELow (33.6%); and T2High-IgEHigh (45.7%). T2Low-IgELow patients have more frequent cardiovascular and metabolic comorbidities, a higher prevalence of emphysema, and higher LAMA use than the two T2High subgroups. Higher exacerbation rates, rhinitis, and anxiety/depression syndrome characterize the T2Low-IgEHigh phenotype vs. the T2Low-IgELow phenotype. Within the T2High, low IgE was associated with female sex, obesity, and anxiety/depression. Conclusions: High IgE in T2Low patients is associated with a peculiar clinical phenotype, similar to T2High in terms of disease severity and nasal comorbidities, while retaining the T2Low features. IgE may represent an additional biomarker for clustering asthma in both T2High and T2Low phenotypes rather than a predictor of T2High asthma "per se".

Effectiveness of FeNO-guided treatment in adult asthma patients: A systematic review and meta-analysis

OBJECTIVE

Asthma control is generally monitored by assessing symptoms and lung function. However, optimal treatment is also dependent on the type and extent of airway inflammation. Fraction of exhaled Nitric Oxide (FeNO) is a noninvasive biomarker of type 2 airway inflammation, but its effectiveness in guiding asthma treatment remains disputed. We performed a systematic review and meta-analysis to obtain summary estimates of the effectiveness of FeNO-guided asthma treatment.

DESIGN

We updated a Cochrane systematic review from 2016. Cochrane Risk of Bias tool was used to assess risk of bias. Inverse-variance random-effects meta-analysis was performed. Certainty of evidence was assessed using GRADE. Subgroup analyses were performed based on asthma severity, asthma control, allergy/atopy, pregnancy and obesity.

DATA SOURCES

The Cochrane Airways Group Trials Register was searched on 9 May 2023.

ELIGIBILITY CRITERIA

We included randomized controlled trials (RCTs) comparing the effectiveness of a FeNO-guided treatment versus usual (symptom-guided) treatment in adult asthma patients.

RESULTS

We included 12 RCTs (2,116 patients), all showing high or unclear risk of bias in at least one domain. Five RCTs reported support from a FeNO manufacturer. FeNO-guided treatment probably reduces the number of patients having ≥1 exacerbation (OR = 0.61; 95%CI 0.44 to 0.83; six RCTs; GRADE moderate certainty) and exacerbation rate (RR = 0.67; 95%CI 0.54 to 0.82; six RCTs; moderate certainty), and may slightly improve Asthma Control Questionnaire score (MD = -0.10; 95%CI -0.18 to -0.02, six RCTs; low certainty), however, this change is unlikely to be clinically important. An effect on severe exacerbations, quality of life, FEV1, treatment dosage and FeNO values could not be demonstrated. There were no indications that effectiveness is different in subgroups of patients, although evidence for subgroup analysis was limited.

CONCLUSIONS

FeNO-guided asthma treatment probably results in fewer exacerbations but may not have clinically important effects on other asthma outcomes.

Immune cell ratio and coagulation markers in assessing prognosis of asthma: a cross-sectional study from Saudi Arabia

Asthma affects a significant number of individuals in Saudi Arabia, with increasing prevalence worldwide, leading to a considerable impact on their quality of life and frequent hospitalizations. In this study, we aimed to explore the relationship between the immune cell ratio and coagulation markers, specifically to identify the occurrence of coagulation abnormalities associated with asthma. To achieve this, we assessed asthma history and severity using a questionnaire while analyzing coagulation biomarkers through venous blood samples. The biomarkers examined included d-dimer, prothrombin time (PT), partial thromboplastin time (PTT), and the international normalized ratio (INR). In addition, we evaluated various hematological parameters such as blood cell counts and hemoglobin (HGB) levels. Our findings revealed compelling evidence, showing significantly elevated levels of d-dimer and the eosinophil-to-neutrophil (ENR) ratio in asthma cases compared to the controls. Moreover, we observed a positive correlation between d-dimer levels and the ENR, with each unit increase in d-dimer associated with a 0.0006 increase in the ENR among asthma cases. These results highlight the potential of assessing ENR and d-dimer levels as predictive indicators for disease prognosis and the development of coagulation abnormalities in individuals with asthma. By shedding light on the relationship between immune cell ratios and coagulation markers in the context of asthma, our study contributes to a better understanding of disease progression and the associated complications. These insights can potentially lead to improved management strategies and better outcomes for asthma patients.

Characteristics of Induced-Sputum Inflammatory Phenotypes in Adults with Asthma: Predictors of Bronchial Eosinophilia

Purpose

The objectives of this study were, for patients attending a specialist asthma clinic at a tertiary care hospital, to determine, from sputum induction (SI), proportions of bronchial inflammatory phenotypes, demographic, clinical and functional characteristics of each phenotype, and the most accessible non-invasive inflammatory marker that best discriminates between phenotypes.

Patients and Methods

Included were 96 patients with asthma, attending a specialist asthma clinic at a tertiary care hospital, who underwent testing as follows: SI, spirometry, fractional exhaled nitric oxide (FeNO), blood eosinophilia, total immunoglobulin E (IgE), and a skin prick test.

Results

SI phenotypes were 46.9% eosinophilic, 33.3% paucigranulocytic, 15.6% neutrophilic, and 4.2% mixed. No significantly different clinical or functional characteristics were observed between the phenotypes. A positive correlation was observed between SI eosinophilia and both emergency visits in the last 12 months (p = 0.041; r = 0.214) and FeNO values (p = 0.000; r = 0.368). Blood eosinophilia correlated with SI eosinophilia (p = 0.001; r = 0.362) and was the best predictor of bronchial eosinophilia, followed by FeNO, and total blood IgE (area under the receiver operating characteristic curve (AUC-ROC) 72%, 65%, and 53%, respectively), although precision was only fair.

Conclusion

In consultations for severe asthma, the most frequent phenotype was eosinophilic. Peripheral blood eosinophilia is a reliable marker for discriminating between different bronchial inflammatory phenotypes, is useful in enabling doctors to select a suitable biologic treatment and so prevent asthma exacerbation, and is a better predictor of bronchial eosinophilia than FeNO and IgE values.

Potential determinants of T helper 2 markers and their distribution in school-aged children

BACKGROUND

There is growing data on T helper 2 (Th2) biomarker determinants in adult populations. However, the determinants and typical range of these biomarkers have not been well studied in general populations of children. Therefore, we assessed the determinants and typical range of three Th2 biomarkers, including blood eosinophils, FeNO, and serum total IgE in 9-11-year-old children in a prospective birth cohort.

METHODS

We examined the pre- and postnatal factors associated with Th2 biomarkers using multivariable logistic regression analysis (n = 428) and extended the results to the original cohort (n = 17,009) using inverse probability weighting. We also measured typical Th2 biomarker distribution in all examined children and healthy participants without allergic diseases (n = 180).

RESULTS

At age 9-11, wheeze (odds ratio (OR) 7.63), rhinitis (OR 3.14), and eczema (OR 2.46) were significantly associated with increased blood eosinophils. All three allergic conditions were associated with FeNO and total serum IgE, but the ORs were smaller than those for blood eosinophils. Secondhand smoking was inversely associated with the blood eosinophils (OR, 0.38). Similar results were found in the original cohort. Male sex and prenatal factors (maternal smoking and parental history of allergies) were not independent predictors of high Th2 levels.

CONCLUSIONS

In addition to wheezing and rhinitis, eczema and secondhand smoke exposure are independent factors for Th2 biomarker interpretation in children. Furthermore, the typical values and cutoff values of blood eosinophils in adults may not be applicable to children.

Identifying clinical and demographic characteristic differences between eosinophilic and non-eosinophilic asthma and detecting predictors of eosinophilic asthma among Egyptian asthmatic patients

Introduction

Asthma is a heterogenous disease with various phenotypes that is characterized by airway limitation due to bronchospasm and airway inflammation associated with excessive mucus secretion. Eosinophilic asthma subtype is described as a late onset asthma that presents with more severe respiratory symptoms, and with sputum eosinophilia ≥ 3%. In the current study, we aimed to identify the difference in the clinical and demographic characteristics between eosinophilic and non-eosinophilic asthma subtypes and to determine predictors of eosinophilic asthma.

Materials and methods

One hundred bronchial asthma patients with age ≥ 18 years were divided into two groups according to sputum eosinophilia. All patients were subjected to medical history, Asthma Control Test (ACT), spirometry, serum IgE level, skin prick testing (SPT), and nasal endoscopy to detect nasal polyposis and allergic signs.

Results

No statistical difference was found between eosinophilic and non-eosinophilic asthma patients regarding age, gender, and body mass index. Patients with sputum eosinophilia had more severe obstruction by spirometry, and positive SPT to food allergens, pollens, and latex with statistical significance (p values 0.001, 0.016, and 0.017 respectively). Additionally, patients with sputum eosinophilia had lower ACT score, higher serum IgE level and higher serum eosinophil count. Total IgE had the highest diagnostic accuracy for discrimination of sputum eosinophilia among asthma patients. Pollen allergy and the severity of airway obstruction by spirometry were independent predictors of eosinophilic asthma.

Conclusion

Patients with eosinophilic asthma had more severe airway obstruction, lower ACT scores, higher serum IgE level, and serum eosinophil count. Pollen allergy and obstructive pattern by spirometry were independent predictors of eosinophilic asthma.

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.

Exacerbation Profile and Risk Factors in a Type-2-Low Enriched Severe Asthma Cohort: A Clinical Trial to Assess Asthma Exacerbation Phenotypes

Rationale: The past 25 years have seen huge progress in understanding of the pathobiology of type-2 (T2) asthma, identification of measurable biomarkers, and the emergence of novel monoclonal antibody treatments. Although present in a minority of patients with severe asthma, very little is known about the mechanisms underlying T2-low asthma, making it a significant unmet need in asthma research. Objectives: The objective of this study was to explore the differences between study exacerbators and nonexacerbators, to describe physiological changes at exacerbation in those who are T2^HIGH and T2^LOW at the time of exacerbation, and to evaluate the stability of inflammatory phenotypes when stable and at exacerbation. Methods: Exacerbation assessment was a prespecified secondary analysis of data from a 48-week, multicenter, randomized controlled clinical study comparing the use of biomarkers and symptoms to adjust steroid treatment in a T2-low severe asthma-enriched cohort. Participants were phenotyped as T2^LOW (fractional exhaled nitric oxide ⩽ 20 ppb and blood eosinophil count ⩽ 150 cells/µl) or T2^HIGH (fractional exhaled nitric oxide > 20 or blood eosinophil count > 150) at study enrollment and at each exacerbation. Here, we report the findings of the exacerbation analyses, including comparison of exacerbators and nonexacerbators, the physiological changes at exacerbation in those who had evidence of T2 biology at exacerbation versus those that did not, and the stability of inflammatory phenotypes when stable and at exacerbation. Measurements and Main Results: Of the 301 participants, 60.8% (183) had one or more self-reported exacerbations (total of 390). Exacerbators were more likely to be female, have a higher body mass index, and have more exacerbations requiring oral corticosteroid and unscheduled primary care attendances for exacerbations. At enrollment, 23.6% (71) were T2^LOW and 76.4% (230) T2^HIGH. The T2^LOW group had more asthma primary care attendances, were more likely to have a previous admission to HDU (high dependency unit)/ICU and to be receiving maintenance oral corticosteroids. At exacerbation, the T2^LOW events were indistinguishable from T2^HIGH exacerbations in terms of lung function (mean fall in T2^LOW FEV_1, 200 [400] ml vs. T2^HIGH 200 [300] ml; P = 0.93) and symptom increase (ACQ5: T2^LOW, 1.4 [0.8] vs. T2^HIGH, 1.3 [0.8]; P = 0.72), with no increase in T2 biomarkers from stable to exacerbation state in the T2^LOW exacerbations. The inflammatory phenotype within individual patients was dynamic; inflammatory phenotype at study entry did not have a significant association with exacerbation phenotype. Conclusions: Asthma exacerbations demonstrating a T2^LOW phenotype were physiologically and symptomatically similar to T2^HIGH exacerbations. T2^LOW asthma was an unstable phenotype, suggesting that exacerbation phenotyping should occur at the time of exacerbation. The clinically significant exacerbations in participants without evidence of T2 biology at the time of exacerbation highlight the unmet and pressing need to further understand the mechanisms at play in non-T2 asthma. Clinical trial registered with www.clinicaltrials.gov (NCT02717689).

Eosinophilic Asthma, Phenotypes-Endotypes and Current Biomarkers of Choice

Asthma phenotyping and endotyping are constantly evolving. Currently, several biologic agents have been developed towards a personalized approach to asthma management. This review will focus on different eosinophilic phenotypes and Th2-associated endotypes with eosinophilic inflammation. Additionally, airway remodeling is analyzed as a key feature of asthmatic eosinophilic endotypes. In addition, evidence of biomarkers is examined with a predictive value to identify patients with severe, uncontrolled asthma who may benefit from new treatment options. Finally, there will be a discussion on the results from clinical trials regarding severe eosinophilic asthma and how the inhibition of the eosinophilic pathway by targeted treatments has led to the reduction of recurrent exacerbations.

Diagnostic Accuracy of Liquid Biomarkers in Airway Diseases: Toward Point-of-Care Applications

Background

Liquid biomarkers have shown increasing utility in the clinical management of airway diseases. Salivary and blood samples are particularly amenable to point-of-care (POC) testing due to simple specimen collection and processing. However, very few POC tests have successfully progressed to clinical application due to the uncertainty and unpredictability surrounding their diagnostic accuracy.

Objective

To review liquid biomarkers of airway diseases with well-established diagnostic accuracies and discuss their prospects for future POC applications.

Methodology

A literature review of publications indexed in Medline or Embase was performed to evaluate the diagnostic accuracy of liquid biomarkers for chronic obstructive pulmonary disease (COPD), asthma, laryngopharyngeal reflux (LPR), and COVID-19.

Results

Of 3,628 studies, 71 fulfilled the inclusion criteria. Sputum and blood eosinophils were the most frequently investigated biomarkers for the management of asthma and COPD. Salivary pepsin was the only biomarker with a well-documented accuracy for the diagnosis of LPR. Inflammatory blood biomarkers (e.g., CRP, D-dimers, ferritin) were found to be useful to predict the severity, complications, and mortality related to COVID-19 infection.

Conclusion

Multiple liquid biomarkers have well-established diagnostic accuracies and are thus amenable to POC testing in clinical settings.

Clinical and cytokine patterns of uncontrolled asthma with and without comorbid chronic rhinosinusitis: a cross-sectional study

Background

Asthma is significantly related to chronic rhinosinusitis (CRS) both in prevalence and severity. However, the clinical patterns of uncontrolled asthma with and without comorbid CRS are still unclear. This study aimed to explore the clinical characteristics and cytokine patterns of patients with uncontrolled asthma, with and without comorbid CRS.

Methods

22 parameters associated with demographic characteristics, CRS comorbidity, severity of airflow obstruction and airway inflammation, and inflammation type of asthma were collected and assessed in 143 patients with uncontrolled asthma. Different clusters were explored using two-step cluster analysis. Sputum samples were collected for assessment of Th1/Th2/Th17 and epithelium-derived cytokines.

Results

Comorbid CRS was identified as the most important variable for prediction of different clusters, followed by pulmonary function parameters and blood eosinophil level. Three clusters of patients were determined: Cluster 1 (n = 46) characterized by non-atopic patients with non-eosinophilic asthma without CRS, demonstrating moderate airflow limitation; Cluster 2 (n = 54) characterized by asthma patients with mild airflow limitation and CRS, demonstrating higher levels of blood eosinophils and immunoglobulin E (IgE) than cluster 1; Cluster 3 (n = 43) characterized by eosinophilic asthma patients with severe airflow limitation and CRS (46.5% with nasal polyps), demonstrating worst lung function, lowest partial pressure of oxygen (PaO₂), and highest levels of eosinophils, fraction of exhaled nitric oxide (FeNO) and IgE. Sputum samples from Cluster 3 showed significantly higher levels of Interleukin (IL)-5, IL-13, IL-33, and tumor necrosis factor (TNF)-α than the other two clusters; and remarkably elevated IL-4, IL-17 and interferon (IFN)-γ compared with cluster 2. The levels of IL-10 and IL-25 were not significantly different among the three clusters.

Conclusions

Uncontrolled asthma may be endotyped into three clusters characterized by CRS comorbidity and inflammatory cytokine patterns. Furthermore, a united-airways approach may be especially necessary for management of asthma patients with Type 2 features.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12931-022-02028-3.

FeNO in Asthma

Asthma is a common disease affecting 350 million people worldwide, which is characterized by airways inflammation and hyperreactivity. Historically diagnosis and treatment have been mainly based on symptoms, which have the potential to result in misdiagnosis and inappropriate treatment. Nitric oxide (NO) is exhaled in human breath and is a marker of airways inflammation. Levels of NO are increased in the exhaled breath of patients with type 2 asthma and fractional exhaled nitric oxide (FeNO) provides an objective biomarker of airway inflammation. FeNO testing is an accessible, noninvasive, and easy-to-use test. Cut-off values have been established by the American Thoracic Society (ATS), the Global Initiative for Asthma (GINA), and the National Institute for Health and Care Excellence (NICE) but vary between guidance. FeNO levels have been shown to be predictive of blood and sputum eosinophil levels but should not be used in isolation and current guidance emphasizes the importance of incorporating clinical symptoms and testing when utilizing FeNO results. The inclusion of FeNO testing can increase diagnostic accuracy of asthma, while high levels in asthmatic patients can help predict response to inhaled corticosteroids (ICS) and suppression of levels with ICS to monitor adherence. FeNO levels are also a predictor of asthma risk with increased exacerbation rates and accelerated decline in lung function associated with high levels as well as having an emerging role in predicting response to some biologic therapies in severe asthma. FeNO testing is cost-effective and has been shown, when combined with clinical assessment, to improve asthma management.

Blood eosinophil counts in the general population and airways disease: a comprehensive review and meta-analysis

BACKGROUND

The clinical context for using blood eosinophil (EOS) counts as treatment-response biomarkers in asthma and COPD requires better understanding of EOS distributions and ranges. We describe EOS distributions and ranges published in asthma, COPD, control (non-asthma/COPD) and general populations.

METHODS

We conducted a comprehensive literature review and meta-analysis of observational studies (January 2008 to November 2018) that included EOS counts in asthma, severe asthma, COPD, control and general populations. Excluded studies had total sample sizes <200, EOS as inclusion criterion, hospitalised population only and exclusively paediatric participants.

RESULTS

Overall, 91 eligible studies were identified, most had total-population-level data available: asthma (39 studies), severe asthma (12 studies), COPD (23 studies), control (seven studies) and general populations (14 studies); some articles reported data for multiple populations. Reported EOS distributions were right-skewed (seven studies). Reported median EOS counts ranged from 157-280 cells·µL-1 (asthma, 22 studies); 200-400 cells·µL-1 (severe asthma, eight studies); 150-183 cells·µL-1 (COPD, six studies); and 100-160 cells·µL-1 (controls, three studies); and 100-200 cells·µL-1 (general populations, six studies). The meta-analysis showed that observed variability was mostly between studies rather than within studies. Factors reportedly associated with higher blood EOS counts included current smoking, positive skin-prick test, elevated total IgE, comorbid allergic rhinitis, age ≤18 years, male sex, spirometric asthma/COPD diagnosis, metabolic syndrome and adiposity.

CONCLUSION

EOS distribution and range varied by study population, and were affected by clinical factors including age, smoking history and comorbidities, which, regardless of severity, should be considered during treatment decision-making.

Airway hyperresponsiveness and inflammation in Japanese patients with human immunodeficiency virus 1 infection

INTRODUCTION

Despite the growing population of long-term survivors with human immunodeficiency virus 1 (HIV) exhibiting asthma-like features worldwide, the pathogenesis underlying airway hyperresponsiveness (AHR) and airway inflammation remains unclear. We aimed to investigate AHR and airway inflammation in an HIV-infected Japanese population.

METHODS

Of 94 Japanese participants, 10 HIV-infected participants with asthma were excluded from the study. We compared the characteristics of HIV-infected (n = 34) and non-HIV-infected participants (n = 50). Eosinophilic, neutrophilic, mixed (eosinophilic and neutrophilic), and paucigranulocytic airway inflammatory phenotypes were classified based on induced sputum characteristics.

RESULTS

The prevalence of AHR in HIV-infected participants (32.4%) was significantly higher than that in their non-HIV-infected counterparts (10.0%) (P = 0.0213). The multivariate nominal logistic regression analysis revealed HIV as an independent risk factor for AHR. HIV-infected participants were significantly more likely to have a neutrophilic airway inflammatory phenotype than non-HIV-infected participants (P = 0.0358). Furthermore, HIV-infected participants with AHR demonstrated a significant correlation between AHR levels and the percentage of sputum neutrophils (r = -0.65, P = 0.0316). The percentage of sputum neutrophils was negatively associated with the blood CD4 cell count (r = -0.66, P = 0.0266).

CONCLUSIONS

We observed the high prevalence of AHR and neutrophilic airway inflammatory phenotype in Japanese participants with stable HIV infection. Our findings provide insight into the mechanisms of AHR and may facilitate the development of novel treatment for individuals with AHR and HIV infection.

Long-term predictors of severe exacerbations and mortality in a cohort of well-characterised adults with asthma

Background

We aimed to explore long-term predictors of severe exacerbations and mortality in adults with well-characterised asthma.

Study design and methods

Adults (aged ≥ 15) with an objectively verified diagnosis of asthma were recruited from a Danish respiratory outpatient clinic between 1974 and 1990. All individuals were followed in Danish registries for vital status, hospital admissions for asthma and cause of death until end of 2017. Predictors of exacerbations were obtained from a repeated measures model. Standardised mortality rates (SMR) for all-causes were compared with the Danish background population. Hazard ratios for mortality were obtained from a cox proportional hazards model in a two-step process.

Results

At baseline, the cohort comprised 1071 patients (mean age 38, SD 16, 61% women), of whom 357 (33%) died during follow-up, with 93 (26%) dying from asthma (primary diagnosis). We found an SMR of 1.24 (95% CI 1.11–1.37, p < 0.001) for all-cause mortality. Baseline predictors for asthma-related death and repeated severe exacerbations were increasing age, ever smoker, FEV₁ < 80% pred., high blood eosinophils, longer duration of symptoms and use of SABA > twice daily. Being non-atopic, having a positive histamine challenge test and symptoms more than twice a week were also predictors of repeated exacerbations.

Conclusions

Markers of poor asthma control, including high use of SABA, are predictors of long-term exacerbation rate and mortality over 30 years in patients with well-characterised asthma. Improving asthma control, including lung function and reducing use of reliever medication, is vital for improving the long-term outcome of asthma.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12931-021-01864-z.

Latest Progresses in Allergic Diseases Biomarkers: Asthma and Atopic Dermatitis

In the last years, the understanding of the pathologic mechanisms of asthma and atopic dermatitis, both characterized by allergic inflammation, has greatly improved. However, it is evident that both diseases present with high heterogeneity, which complicates the diagnosis and the therapeutic approach of the patients. Moreover, some of the currently available strategies to treat asthma and atopic dermatitis are still mostly controlling the symptoms, but not to lead towards full healing, thus having these two diseases labelled as unmet clinical needs by WHO. Therefore, the "one-size-fits-all" strategy is outdated for asthma and atopic dermatitis, and there is the need of better methods to clearly diagnose the disease and tailor the therapy according to the specific symptomatology. In this regard, the use of biomarkers has been advanced in order to characterize both diseases according to their clinical signs and to facilitate the subsequent treatment. Despite the advancements made in this regard, there is still need for better and more sensitive biomarkers and for less invasive sampling methodologies, with the aim to diagnose specifically each manifestation of asthma and atopic dermatitis and to provide the best treatment with the least suffering for the patients.

Using FeNO Measurement in Clinical Asthma Management

Asthma is a common and heterogeneous disease, characterised by lower airway inflammation and airflow limitation. Critical factors in asthma management include establishing an accurate diagnosis and ensuring appropriate selection and dosage of anti-inflammatory therapies. The majority of asthma patients exhibit type 2 (T2) inflammation, with increased interleukin (IL)-4, IL-5, and IL-13 signalling, often with associated eosinophilia. Identifying lower airway eosinophilia with sputum induction improves asthma outcomes, but is time consuming and costly. Increased T2-inflammation leads to upregulation of nitric oxide (NO) release into the airway, with increasing fractional exhaled NO (FeNO) reflecting greater T2-inflammation. FeNO can be easily and quickly measured in the clinic, offering a point of care surrogate measure of the degree of lower airway inflammation. FeNO testing can be used to help confirm an asthma diagnosis, to guide inhaled corticosteroid therapy, to assess adherence to treatment, and to aid selection of appropriate biologic therapy. However, FeNO levels may also be influenced by a variety of intrinsic and extrinsic factors other than asthma, including nasal polyposis and cigarette smoking, and must be interpreted in the broader clinical context rather than viewed in isolation. This review discusses the clinical application of FeNO measurement in asthma care, from diagnosis to treatment selection, and describes its place in current international expert guidelines.

Metabolomics, Microbiota, and In Vivo and In Vitro Biomarkers in Type 2 Severe Asthma: A Perspective Review

Precision medicine refers to the tailoring of therapeutic strategies to the individual characteristics of each patient; thus, it could be a new approach for the management of severe asthma that considers individual variability in genes, environmental exposure, and lifestyle. Precision medicine would also assist physicians in choosing the right treatment, the best timing of administration, consequently trying to maximize drug efficacy, and, possibly, reducing adverse events. Metabolomics is the systematic study of low molecular weight (bio)chemicals in a given biological system and offers a powerful approach to biomarker discovery and elucidating disease mechanisms. In this point of view, metabolomics could play a key role in targeting precision medicine.

Metabolomics, Microbiota, and In Vivo and In Vitro Biomarkers in Type 2 Severe Asthma: A Perspective Review

Precision medicine refers to the tailoring of therapeutic strategies to the individual characteristics of each patient; thus, it could be a new approach for the management of severe asthma that considers individual variability in genes, environmental exposure, and lifestyle. Precision medicine would also assist physicians in choosing the right treatment, the best timing of administration, consequently trying to maximize drug efficacy, and, possibly, reducing adverse events. Metabolomics is the systematic study of low molecular weight (bio)chemicals in a given biological system and offers a powerful approach to biomarker discovery and elucidating disease mechanisms. In this point of view, metabolomics could play a key role in targeting precision medicine.

Impact of Blood Eosinophil Variability in Asthma: A Real-Life Population Study

RATIONALE

Blood eosinophil count predicts response to inhaled corticosteroids and specific biologic therapies in selected asthma patients. Despite this important role, fundamental aspects of eosinophil behavior in asthma have not been studied. Objectives To investigate the behavior of blood eosinophils in a population comparing their distribution with the general population and studying their intra-individual variability over time in relation to hospital episodes (emergency department visits and hospitalizations) in clinical practice.

METHODS

The distribution and variability of 35,703 eosinophil determinations in 10,059 stable asthma patients were investigated in the Majorca Real-Life Investigation in COPD and Asthma cohort (MAJORICA). Eosinophil distribution in the asthma population was compared with a control sample from the general population of 8,557 individuals. Eosinophil variability and hospital episodes were analyzed using correlations, ROC curves and multiple regression analysis. We defined the Eosinophil Variability Index (EVI) as (Eosmax-Eosmin/Eosmax) x 100%. The findings of the asthma population were re-tested in an external well-characterized asthma cohort.

RESULTS

The eosinophil count values and variability were higher in the asthma population than in the general population (p-value<0.001). Variability data showed a better association with hospital episodes than the counting values. An EVI≥50% was more strongly associated with hospital episodes than any of the absolute counting values. These results were validated in the external cohort.

CONCLUSION

The eosinophil variability in asthma patients better identifies the risk of any hospital episode than the absolute counting values currently used to target specific treatments.

Will the asthma revolution fostered by biologics also benefit adult ICU patients?

PURPOSE

Asthma exacerbations are inflammatory events that rarely result in full hospitalization following an ER visit. Unfortunately, certain patients require prolonged support, including occasional external lung support through ECMO or ECCOR (with subsequent further exposure to other life-threatening issues), and some die. In parallel, biologics are revolutionizing severe asthma management, mostly in T2 high patients.

METHODS

We extensively reviewed the current unmet needs surrounding ICU-admitted asthma exacerbations, with a focus on currently available drugs and the underlying biological processes involved. We explored whether currently available T2-targeting drugs can reasonably be seen as potential players not only for relapse prevention but also as candidate drugs for a faster resolution of such episodes. The patient's perspective was also sought.

RESULTS

About 30% of asthma exacerbations admitted to the ICU do not resolve within five days. Persistent severe airway obstruction despite massive doses of corticosteroids and maximal pharmacologically induced bronchodilation is the main cause of treatment failure. Previous ICU admission is the main risk factor for such episodes and may eventually be considered as a T2 surrogate marker. Fatal asthma cases are hallmarked by poorly steroid-sensitive T2-inflammation associated with severe mucus plugging. New, fast-acting T2-targeting biologics (already used for preventing asthma exacerbations) have the potential to circumvent steroid sensitivity pathways and decrease mucus plugging. This unmet need was confirmed by patients who reported highly negative, traumatizing experiences.

CONCLUSIONS

There is room for improvement in the management of ICU-admitted severe asthma episodes. Clinical trials assessing how biologics might improve ICU outcomes are direly needed.

COL4A3 is degraded in allergic asthma and degradation predicts response to anti-IgE therapy

BACKGROUND

Asthma is a heterogeneous syndrome substantiating the urgent requirement for endotype-specific biomarkers. Dysbalance of fibrosis and fibrolysis in asthmatic lung tissue leads to reduced levels of the inflammation-protective collagen 4 (COL4A3).

OBJECTIVE

To delineate the degradation of COL4A3 in allergic airway inflammation and evaluate the resultant product as a biomarker for anti-IgE therapy response.

METHODS

The serological COL4A3 degradation marker C4Ma3 (Nordic Bioscience, Denmark) and serum cytokines were measured in the ALLIANCE cohort (pediatric cases/controls: 134/35; adult cases/controls: 149/31). Exacerbation of allergic airway disease in mice was induced by sensitising to OVA, challenge with OVA aerosol and instillation of poly(cytidylic-inosinic). Fulacimstat (chymase inhibitor, Bayer) was used to determine the role of mast cell chymase in COL4A3 degradation. Patients with cystic fibrosis (CF, n=14) and CF with allergic broncho-pulmonary aspergillosis (ABPA, n=9) as well as severe allergic, uncontrolled asthmatics (n=19) were tested for COL4A3 degradation. Omalizumab (anti-IgE) treatment was assessed by the Asthma Control Test.

RESULTS

Serum levels of C4Ma3 were increased in asthma in adults and children alike and linked to a more severe, exacerbating allergic asthma phenotype. In an experimental asthma mouse model, C4Ma3 was dependent on mast cell chymase. Serum C4Ma3 was significantly elevated in CF plus ABPA and at baseline predicted the success of the anti-IgE therapy in allergic, uncontrolled asthmatics (diagnostic odds ratio 31.5).

CONCLUSION

C4Ma3 level depend on lung mast cell chymase and are increased in a severe, exacerbating allergic asthma phenotype. C4Ma3 may serve as a novel biomarker to predict anti-IgE therapy response.

T2-High Endotype and Response to Biological Treatments in Patients with Bronchiectasis

Although bronchiectasis pathophysiology has been historically understood around the presence of airway neutrophilic inflammation, recent experiences are consistent with the identification of a type 2 inflammation (T2) high endotype in bronchiectasis. In order to evaluate prevalence and clinical characteristics of bronchiectasis patients with a T2-high endotype and explore their response to biologicals, two studies were carried out. In a cross-sectional study, bronchiectasis adults without asthma underwent clinical, radiological, and microbiological assessment, along with blood eosinophils and oral fractional exhaled nitric oxide (FeNO) evaluation, during stable state. Prevalence and characteristics of patients with a T2- high endotype (defined by the presence of either eosinophils blood count ≥300 cells·µL⁻¹ or oral FeNO ≥ 25 dpp) were reported. A case series of severe asthmatic patients with concomitant bronchiectasis treated with either mepolizumab or benralizumab was evaluated, and patients’ clinical data pre- and post-treatment were analyzed up to 2 years of follow up. Among bronchiectasis patients without asthma enrolled in the cross-sectional study, a T2-high endotype was present in 31% of them. These patients exhibited a more severe disease, high dyspnea severity, low respiratory function, and high impact on quality of life. Among the five patients with severe eosinophilic asthma and concomitant bronchiectasis included in the series, treatment with either mepolizumab or benralizumab significantly reduced the exacerbation rate with an effect that persists for up to 2 years of follow up. If validated across different settings, our data suggest the need to design randomized controlled trials on biological treatments targeting the T2-high endotype in bronchiectasis patients.

A Current Perspective of Allergic Asthma: From Mechanisms to Management

Asthma is a result of heterogenous, complex gene-environment interactions with variable clinical phenotypes, inflammation, and remodeling. It affects more than 330 million of people worldwide throughout their educational and working lives, while exacerbations put a heavy cost/burden on productivity. Childhood asthma is characterized by a predominance of allergic sensitization and multimorbidity, while in adults polysensitization has been positively associated with asthma occurrence. Despite significant improvements in recent decades, asthma management remains challenging. Recently, a group of specialists suggested that the term "asthma" should be preferably used as a descriptive term for symptoms. Moreover, type 2 inflammation has emerged as a pivotal disease mechanism including overlapping endotypes of specific IgE production, while type 2-low asthma includes several disease endotypes. Optimal asthma control requires both appropriate pharmacological interventions, tailored to each patient, as well as trigger avoidance measures. Regular monitoring for maintenance of symptom control, preservation of lung function, and detection of treatment-related adverse effects are warranted. Allergen-specific immunotherapy and the advent of new targeted therapies for patients with difficult to control asthma offer diverse treatment options. The current review summarizes up-to-date knowledge on epidemiology, definitions, diagnosis, and current therapeutic strategies.

Biomarkers in Different Asthma Phenotypes

Asthma is the most common respiratory disease. It has multiple phenotypes thatcan be partially differentiated by measuring the disease’s specific characteristics—biomarkers. The pathogenetic mechanisms are complex, and it is still a challenge to choose suitable biomarkers to adequately stratify patients, which became especially important with the introduction of biologicals in asthma treatment. Usage of biomarkers and an understanding of the underlying pathobiological mechanisms lead to the definition of endotypes. Asthma can be broadly divided into two endotypes, T2-high and T2-low. The right combination of various biomarkers in different phenotypes is under investigation, hoping to help researchers and clinicians in better disease evaluation since theindividual approach and personalized medicine are imperative. Multiple biomarkers are superior to a single biomarker.

Diagnosis and Management of T2-High Asthma

Type 2 (T2) inflammation plays a key role in the pathogenesis of asthma. IL-4, IL-5, and IL-13, along with other inflammatory mediators, lead to increased cellular eosinophilic inflammation. It is likely that around half of all patients with asthma have evidence of T2-high inflammation. Sputum and blood eosinophils, exhaled nitric oxide, blood IgE levels, and airway gene expression markers are frequently used biomarkers of T2-high asthma. Individuals with T2-high asthma tend to have several features of increased asthma severity, including reduced lung function and increased rates of asthma exacerbations, and T2-high patients demonstrate distinct pathologic features including increased airway remodeling and alterations in airway mucus production. Several monoclonal antibodies are now available to treat individuals with T2-high asthma and these medications significantly reduce asthma exacerbation rates.

The central role of IL-33/IL-1RL1 pathway in asthma: From pathogenesis to intervention

Interleukin-33 (IL-33), a member of the IL-1 family, and its cognate receptor, Interleukin-1 receptor like-1 (IL-1RL1 or ST2), are susceptibility genes for childhood asthma. In response to cellular damage, IL-33 is released from barrier tissues as an 'alarmin' to activate the innate immune response. IL-33 drives type 2 responses by inducing signalling through its receptor IL-1RL1 in several immune and structural cells, thereby leading to type 2 cytokine and chemokine production. IL-1RL1 gene transcript encodes different isoforms generated through alternative splicing. Its soluble isoform, IL-1RL1-a or sST2, acts as a decoy receptor by sequestering IL-33, thereby inhibiting IL1RL1-b/IL-33 signalling. IL-33 and its receptor IL-1RL1 are therefore considered as putative biomarkers or targets for pharmacological intervention in asthma. This review will provide an overview of the genetics and biology of the IL-33/IL-1RL1 pathway in the context of asthma pathogenesis. It will discuss the potential and complexities of targeting the cytokine or its receptor, how genetics or biomarkers may inform precision medicine for asthma targeting this pathway, and the possible positioning of therapeutics targeting IL-33 or its receptor in the expanding landscape of novel biologicals applied in asthma management.

Eosinophilic asthma and the role of monoclonal antibodies

ABSTRACT

Eosinophilic asthma presents with continuous airway inflammation resistant to inhaled corticosteroids but responsive to oral glucocorticoids and monoclonal antibodies. Diagnostic criteria include significantly elevated blood or sputum eosinophils and/or fractional exhaled nitric oxide. Five monoclonal antibodies are used for treatment, with accurate diagnosis and early intervention essential to better outcomes.

Associations of dermal diethyl phthalate level with changes in lung function test value mediated by absolute eosinophil count: A panel study of adults in southern Taiwan

Phthalate concentrations in indoor and outdoor dust are associated with respiratory disease. Both immunoglobulin E (IgE) and eosinophil count are associated with airway inflammation from exposure to environmental allergens. Dermal phthalate level can be used as a matrix for assessing personal exposure through direct absorption from the air, particle deposition, or contact with contaminated products. However, the association between dermal phthalate level and changes in lung function test values, as mediated by immunological response, remains unclear. In total, 237 adults in southern Taiwan were recruited. Spirometry measurements (in L) of forced expiratory volume in 1 s (FEV1) and forced vital capacity (FVC) were taken on visits 1 (2016-2018) and 2 (2019). Dermal phthalate level, absolute eosinophil count, and IgE level were recorded on visit 1. Mean changes in FVC and FEV1 decrease pear year, as determined through pairwise comparisons, were significant (^diffFVC_{per year}: -0.46, 95% CI: -0.51, -0.41; p < 0.001; ^diffFEV1_{per year}: -0.37, 95% confidence interval [CI]: -0.41, -0.34; p < 0.001). For FEV1 decrease, log-unit increases in dermal diethyl phthalate (DEP) were positively associated with ^diffFEV1_{per year} (β = 0.096; 95% CI: 0.042, 0.150; p = 0.001) and negatively associated with absolute eosinophil count (β= -0.201; 95% CI: -0.380, -0.023; p= 0.027). Log-unit increases in absolute eosinophil count were negatively associated with ^diffFEV1_{per year} (β= -0.109; 95% CI: -0.150, -0.068; p < 0.001). Absolute eosinophil count mediated 19.70% of the association between dermal DEP level and ^diffFEV1_{per year}. For FVC decrease, log-unit increases in dermal DEP were positively associated with ^diffFVC_{per year} (β = 0.095; 95% CI: 0.035, 0.155; p = 0.002) and negatively associated with absolute eosinophil count (β = -0.243; 95% CI: -0.427, -0.060; p = 0.010). Log-unit increases in absolute eosinophil count were negatively associated with ^diffFVC_{per year} (β= -0.122; 95% CI: -0.168, -0.076; p < 0.001). Absolute eosinophil count mediated 29.98% of the association between dermal DEP level and ^diffFVC_{per year}. The results suggest that dermal DEP level is positively associated with changes in lung function test values and is mediated by absolute eosinophil count.

Choice of biologics in asthma endotypes

PURPOSE OF REVIEW

The aim of this study was to highlight the phenotypes and endotypes of asthma as a tool for selection of the Food and Drug Administration approved biologic therapies.

RECENT FINDINGS

An evolving concept of asthma has led to the identification of distinct phenotypes and endotypes in this disease. Asthma endotypes are defined as the biological mechanism and are often categorized as T2-high and T2-low based on the influence of T helper type 2 (T2) cells and type 2 cytokines, including interleukin (IL)-4, IL-5, IL-9 and IL-13. Biomarkers such as peripheral blood absolute eosinophil count, total IgE, specific IgE and fractional exhaled nitric oxide may be used as indicators of asthma endotypes and help predict response to biologic therapies. There are currently five biologic therapies approved as a treatment option for T2-high asthma: omalizumab, benralizumab, mepolizumab, reslizumab and dupilumab.

SUMMARY

Here, we explore the current understandings of asthma endotypes and review their associated phenotypes. We provide practical and evidence-based guidance for clinicians considering a biologic for asthma add-on maintenance therapy.

Automated cell differential count in sputum is feasible and comparable to manual cell count in identifying eosinophilia

INTRODUCTION

Cell differential count (CDC) of induced sputum is considered the gold standard for inflammatory phenotyping of asthma but is not implemented in routine care due to its heavy time- and staff demands. Digital Cell Morphology is a technique where digital images of cells are captured and presented preclassified as white blood cells (neutrophils, eosinophils, lymphocytes, macrophages, and unidentified) and nonwhite blood cells for review. With this study, we wanted to assess the accuracy of an automated CDC in identifying the key inflammatory cells in induced sputum.

METHODS

Sputum from 50 patients with asthma was collected and processed using the standard processing protocol with one drop 20% albumin added to hinder cell smudging. Each slide was counted automatically using the CellaVision DM96 and manually by an experienced lab technician. Sputum was classified as eosinophilic or neutrophilic using 3% and 61% cutoffs, respectively.

RESULTS

We found a good agreement using intraclass correlation for all target cells, despite significant differences in the cell count rate. The automated CDC had a sensitivity of 65%, a specificity of 93%, and a kappa-coefficient of 0.61 for identification of sputum eosinophilia. In contrast, the automated CDC had a sensitivity of 29%, a specificity of 100%, and a kappa-coefficient of 0.23 for identification of sputum neutrophilia.

CONCLUSION

Automated- and manual cell counts of sputum agree with regards to the key inflammatory cells. The automated cell count had a modest sensitivity but a high specificity for the identification of both neutrophil and eosinophil asthma.

Targeting eosinophils in respiratory diseases: Biological axis, emerging therapeutics and treatment modalities

Eosinophils are bi-lobed, multi-functional innate immune cells with diverse cell surface receptors that regulate local immune and inflammatory responses. Several inflammatory and infectious diseases are triggered with their build up in the blood and tissues. The mobilization of eosinophils into the lungs is regulated by a cascade of processes guided by Th2 cytokine generating T-cells. Recruitment of eosinophils essentially leads to a characteristic immune response followed by airway hyperresponsiveness and remodeling, which are hallmarks of chronic respiratory diseases. By analysing the dynamic interactions of eosinophils with their extracellular environment, which also involve signaling molecules and tissues, various therapies have been invented and developed to target respiratory diseases. Having entered clinical testing, several eosinophil targeting therapeutic agents have shown much promise and have further bridged the gap between theory and practice. Moreover, researchers now have a clearer understanding of the roles and mechanisms of eosinophils. These factors have successfully assisted molecular biologists to block specific pathways in the growth, migration and activation of eosinophils. The primary purpose of this review is to provide an overview of the eosinophil biology with a special emphasis on potential pharmacotherapeutic targets. The review also summarizes promising eosinophil-targeting agents, along with their mechanisms and rationale for use, including those in developmental pipeline, in clinical trials, or approved for other respiratory disorders.

Applying personalized medicine to adult severe asthma

Background: Severe asthma is a heterogeneous disease that consists of various phenotypes driven by different pathways. Associated with significant morbidity, an important negative impact on the quality of life of patients, and increased health care costs, severe asthma represents a challenge for the clinician. With the introduction of various antibodies that target type 2 inflammation (T2) pathways, severe asthma therapy is gradually moving to a personalized medicine approach. Objective: The purpose of this review was to emphasize the important role of personalized medicine in adult severe asthma management. Methods: An extensive research was conducted in medical literature data bases by applying terms such as "severe asthma" associated with "structured approach," "comorbidities," "biomarkers," "phenotypes/endotypes," and "biologic therapies." Results: The management of severe asthma starts with a structured approach to confirm the diagnosis, assess the adherence to medications and identify confounding factors and comorbidities. The definition of phenotypes or endotypes (phenotypes defined by mechanisms and identified through biomarkers) is an important step toward the use of personalized medicine in asthma. Severe allergic and nonallergic eosinophilic asthma are two defined T2 phenotypes for which there are efficacious targeted biologic therapies currently available. Non-T2 phenotype remains to be characterized, and less efficient target therapy exists. Conclusion: Despite important progress in applying personalized medicine to severe asthma, especially in T2 inflammatory phenotypes, future research is needed to find valid biomarkers predictive for the response to available biologic therapies to develop more effective therapies in non-T2 phenotype.

A snapshot of exhaled nitric oxide and asthma characteristics: experience from high to low income countries

Nitric oxide is a gas produced in the airways of asthmatic subjects and related to T2 inflammation. It can be measured as fractional nitric oxide (FeNO) in the exhaled air and used as a non-invasive, easy to evaluate, rapid marker. It is now widely used in many settings to determine airway inflammation. The aim of this narrative review is to report relationship between FeNO and the physiopathologic characteristics of asthmatic patients. Factors affecting FeNO levels have also been analysed as well as the impact of corticosteroid, target therapies and rehabilitation programs. Considering the availability of the test, spreading this methodology to low income countries has also been considered as a possibility for evaluating airway inflammation and monitoring adherence to inhaled corticosteroid therapy. PubMed data search has been performed restricted to English language papers. Research was limited to studies in adults unless studies in children were the only ones reported for a particular issue. This revision could be useful to summarize the role of FeNO in relation to asthma characteristics and help in the use of FeNO in different clinical settings particularly in low income countries.

Upper and lower airway inflammation in severe asthmatics: a guide for a precision biologic treatment

Background and aims:

Severe asthma may require the prescription of one of the biologic drugs currently available, using surrogate markers of airway inflammation (serum IgE levels and allergic sensitization for anti-IgE, or blood eosinophils for anti-IL5/IL5R). Our objective: to assess upper and lower airway inflammation in severe asthmatics divided according to the eligibility criteria for one of the target biologic treatments.

Methods:

We selected 91 severe asthmatics, uncontrolled despite high-dose ICS-LABA, and followed for >6 months with optimization of asthma treatment. Patients underwent clinical, functional and biological assessment, including induced sputum and nasal cytology. They were then clustered according to the eligibility criteria for omalizumab or mepolizumab/benralizumab.

Results:

Four clusters were selected: A (eligible for omalizumab, n = 23), AB (both omalizumab and mepolizumab, n = 26), B (mepolizumab, n = 22) and C (non-eligible for both omalizumab and mepolizumab, n = 20). There was no difference among clusters for asthma control (Asthma Control Test and Asthma Control Questionnaire 7), pre-bronchodilator forced expiratory volume in 1 s, serum IgE and fractional exhaled nitric oxide levels. Sputum eosinophils were numerically higher in clusters AB and B, in agreement with the higher levels of blood eosinophils. Allergic rhinitis was more frequent in clusters A and AB, while chronic rhinosinusitis with nasal polyps prevalence increased progressively from A to C. Eosinophils in nasal cytology were higher in clusters AB, B and C.

Conclusion:

Eosinophilic upper and lower airway inflammation is present in the large majority of severe asthmatics, independently from the prescription criteria for the currently available biologics, and might suggest the use of anti-IL5/IL5R or anti IL4/13 also in patients without blood eosinophilia.

The reviews of this paper are available via the supplemental material section.

Remission and Changes in Severity Over 30 Years in an Adult Asthma Cohort

BACKGROUND

Long-term follow-up studies of adults with well-characterized asthma are sparse.

OBJECTIVE

We aimed to examine long-term remission and change in disease severity over 30 years in adults with asthma.

METHODS

A total of 125 individuals diagnosed with asthma between 1974 and 1990 at a Danish respiratory and allergy clinic, based on history and objective assessments, were included. At follow-up (2017-2019), participants completed questionnaires and had spirometry, bronchodilator reversibility, airway responsiveness, and blood biomarkers measured. Based on these assessments, participants were classified as having either active asthma, clinical remission (no symptoms or prescribed asthma medication within the last year), or complete remission (fractional exhaled nitric oxide <50 parts per billion, no bronchodilator reversibility, no airway hyperresponsiveness, and no airflow limitation). Changes in severity were determined according to Global Initiative for Asthma guidelines based on symptom control and currently prescribed medication.

RESULTS

At follow-up, 25% (n = 31) and 15% (n = 19), respectively, had clinical and complete remission. Our analyses showed that a longer duration of symptoms before the initial assessment (odds ratio, 0.86; 95% confidence interval, 0.75-0.98) was associated with a lower chance of asthma remission. At follow-up, 30% had well-controlled asthma compared with none at baseline. Female sex, previous severe exacerbation(s), and older age at baseline were associated with uncontrolled asthma at follow-up. Blood-eosinophil count (≥0.3 × 10⁹/L) and prescribed inhaled corticosteroid (ICS) at baseline were associated with being prescribed medium/high-dose ICS at follow-up.

CONCLUSION

Despite 30 years of follow-up, asthma rarely remits in adults, especially in individuals with longer duration and presumably more severe disease. Initial signs of pronounced disease activity were associated with uncontrolled asthma at follow-up.

The Prevalence of Subtypes of Type 2 Inflammation in an Unselected Population of Patients with Severe Asthma

BACKGROUND

With the introduction of different targeted therapies for type 2 (T2)-high asthma, there is an urgent need for markers to guide the choice of treatment. T2-high asthma includes different clinical phenotypes of asthma, but the prevalence and impact of activation of different T2 inflammatory pathways is unknown.

OBJECTIVE

To describe the level of coexpression of clinically available T2 inflammatory markers in patients with severe asthma, and the relationship with clinical characteristics and comorbidities.

METHODS

Patients with severe asthma according to European Respiratory Society/American Thoracic Society guidelines were examined prospectively including sputum induction and grouped according to T2 biomarkers: blood eosinophilia (≥0.3 × 10⁹/L), total IgE (≥150 U/mL), and fractional exhaled nitric oxide (≥25 parts per billion).

RESULTS

We found 116 (70%) of the 166 patients to have at least 1 T2 biomarker elevated: 39% had 2 or more elevated biomarkers, whereas 31% had only 1 biomarker elevated. Concomitant airway and systemic eosinophilia was present in 28% of all patients, corresponding to half (53%) of the patients with either. Expression patterns of the T2 biomarkers were associated with differences in allergic sensitization and the coexistence of nasal polyposis.

CONCLUSIONS

Most patients with severe asthma showed at least 1 T2 inflammatory trait. Coexpression of T2 biomarkers was highly heterogeneous, and different expression patterns were associated with distinct clinical characteristics.

Eosinophils in COPD-Current Concepts and Clinical Implications

In recent years, heterogeneity in chronic obstructive pulmonary disease (COPD) inflammatory patterns has been recognized as a basis for more precise treatment interventions because current therapies have limited effectiveness. Eosinophilic airway inflammation in COPD has become a subject of research interest as a potential treatment target for inhaled corticosteroid therapy. However, the role of eosinophils in COPD is still unclear, and it is unknown why only some patients with COPD develop eosinophilic airway inflammation. Induced sputum analysis is the most common method of assessing the type of airway inflammation. Accessibility to sputum induction, however, is limited in clinical practice, and blood eosinophils have been proposed to serve as a surrogate marker and treatment guide. Blood eosinophil count has been shown to poorly predict sputum eosinophilia, and, moreover, it seems to be fairly unstable and affected by various factors. Nevertheless, in several trials, blood eosinophil count appeared to predict good response to inhaled corticosteroids However, biologics targeting eosinophils do not appear to be effective in COPD. In this review, we briefly summarize the current knowledge on eosinophils in COPD pathogenesis. Then, we discuss the use of blood eosinophil count in COPD in relation to the recent Global Initiative for Chronic Obstructive Pulmonary Disease recommendations, their ability to predict sputum eosinophilia, and their potential role in guiding treatment.

Multidimensional Assessment of Asthma Identifies Clinically Relevant Phenotype Overlap: A Cross-Sectional Study

BACKGROUND

Asthma is a heterogeneous disease with multiple phenotypes; however, the relevance of phenotype overlap remains largely unexplored.

OBJECTIVE

To examine the relationship between phenotype overlap and clinical and inflammatory profiles of asthma.

METHODS

In this cross-sectional study, adult participants with stable asthma (n = 522) underwent multidimensional assessments. The 10 most common phenotypes of asthma were defined and then classified into those commonly associated with Type (T) 2 or non-T2 inflammation. Furthermore, phenotype overlap scores (POS), representing the cumulative concomitant phenotypes, were used to analyze its association with clinical and inflammatory asthmatic profiles.

RESULTS

Among the 522 participants, 73.4% (n = 383) had phenotype overlap, and mixed T2 and non-T2 inflammation coexisted in 47.5% (n = 248). T2 POS was positively associated with eosinophils, IgE, and fractional exhaled nitric oxide (FeNO), and negatively with Asthma Quality of Life Questionnaire (AQLQ), sputum neutrophils, IL-17A, IL-8, and TNF-α. Non-T2 POS was positively associated with Asthma Control Questionnaire, neutrophils and sputum IL-8, and negatively with AQLQ, forced expiratory volume in 1 s, blood eosinophils, IgE, and FeNO (all P < .05). Patients with phenotypes that are associated with mixed T2 and non-T2 inflammation had elevated T2 inflammation biomarkers but worse asthma control. Both T2 (adjusted β = -0.191, P = .035) and non-T2 (adjusted β = 0.310, P < .001) POS were significantly associated with severe exacerbations.

CONCLUSIONS

Phenotype overlap is extremely common in asthmatic patients and significantly associated with clinical and inflammatory profiles. Patients with phenotypes associated with mixed T2 and non-T2 inflammation might be unresponsive to medications owing to increased non-T2 inflammation. Multidimensional asthma assessment identifies clinically relevant phenotype overlap.

An official JRS statement: The principles of fractional exhaled nitric oxide (FeNO) measurement and interpretation of the results in clinical practice

Nitric oxide (NO) is produced in the body and has been shown to have diverse actions in the abundance of research that has been performed on it since the 1970s, leading to Furchgott, Murad, and Ignarro receiving the Nobel Prize in Physiology or Medicine in 1998. NO is produced by nitric oxide synthase (NOS). NOS is broadly distributed, being found in the nerves, blood vessels, airway epithelium, and inflammatory cells. In asthma, inflammatory cytokines induce NOS activity in the airway epithelium and inflammatory cells, producing large amounts of NO. Measurement of fractional exhaled nitric oxide (FeNO) is a simple, safe, and quantitative method of assessing airway inflammation. The FeNO measurement method has been standardized and, in recent years, this noninvasive test has been broadly used to support the diagnosis of asthma, monitor airway inflammation, and detect asthma overlap in chronic obstructive pulmonary disease (COPD) patients. Since the normal upper limit of FeNO for healthy Japanese adults is 37 ppb, values of 35 ppb or more are likely to be interpreted as a signature of inflammatory condition presenting features with asthma, and this value is used in clinical practice. Research is also underway for clinical application of these measurements in other respiratory diseases such as COPD and interstitial lung disease. Currently, there remains some confusion regarding the significance of these measurements and the interpretation of the results. This statement is designed to provide a simple explanation including the principles of FeNO measurements, the measurement methods, and the interpretation of the measurement results.

Clinical use of biologics for asthma treatment by allergy specialists: A questionnaire survey

BACKGROUND

Asthma is a heterogeneous disease with emerging phenotypes and endotypes. At present, 5 distinct biologics are Food and Drug Administration-approved as an add-on therapy for difficult-to-control type 2-high asthma. Because allergy specialists manage a spectrum of diseases for which biologics may be appropriate, it is important to understand their prescribing patterns.

OBJECTIVE

To elucidate the allergist's use of biologics in the treatment of asthma, including barriers, preferences, indications for prescribing, measures to determine effectiveness, and cost-effectiveness.

METHODS

A survey was performed among allergists using a semistructured 10-item self-administered web-based questionnaire and the responses were analyzed using one-way frequencies and multiple logistic regression.

RESULTS

The response rate was approximately 9%. Omalizumab was the most prescribed biologic for asthma (98%), and "uncontrolled asthma despite adherence to controller medication" was the most common reason. The common selection criteria among the biologics included elevated peripheral eosinophil count, asthma with nasal polyps, and asthma type (type 1; type 2; nonallergic). A decreased exacerbation frequency was the best standard to determine the efficacy among biologics. Benralizumab was considered the most cost-effective.

CONCLUSION

This study represents one of the largest surveys among allergy specialists regarding the real-world use of asthma biologics. It seems that there has been reasonably good dissemination and application of current guidelines among allergists based on prescribing patterns. However, their responses reflect the need for the continued modification of asthma guidelines that incorporate novel biologics and other pathway-specific agents into step therapy. As clinical phenotypes and predictive biomarkers develop, allergy specialists will be better prepared to practice precision medicine that optimizes the use of asthma biologics.

Spontaneous sputum discriminates inflammatory phenotypes in patients with asthma

BACKGROUND

Eosinophils in induced sputum are not only a useful biomarker for diagnosing asthma but are also associated with severe asthma. However, little is known about the association between eosinophils in spontaneous sputum and asthma severity.

OBJECTIVE

To investigate whether spontaneous sputum eosinophils are related to severe asthma in adult patients with asthma.

METHODS

We conducted a retrospective cross-sectional study on 86 people with asthma whose spontaneous sputa were successfully collected. Patients were classified into 4 phenotypes according to the eosinophil and neutrophil levels in spontaneous sputum. We determined the association between inflammatory phenotypes and severe asthma. Moreover, we also compared asthma severity among the phenotypes classified according to blood eosinophils and spontaneous sputum eosinophils.

RESULTS

Asthma phenotypes were as follows: paucigranulocytic, 30.2%; neutrophilic, 18.6%; eosinophilic, 32.6%; and mixed, 18.6%. People with eosinophilic asthma had the highest blood eosinophils, total immunoglobulin E (IgE), and fractional exhaled nitric oxide among the 4 phenotypes. Significant differences were observed in asthma severity between the phenotypes (P = .019). In particular, 57.2% and 56.2% of patients had severe eosinophilic asthma and mixed asthma, respectively. The logistic regression analysis revealed that spontaneous sputum eosinophilia represented the strongest association with severe asthma among the inflammatory variables. Finally, more patients with severe asthma were included in the phenotype with spontaneous sputum eosinophils greater than 3% and blood eosinophils less than or equal to 300/μL and in the phenotype with spontaneous sputum eosinophils greater than 3% and blood eosinophils greater than 300/μL.

CONCLUSION

Spontaneous sputum can provide helpful information on airway inflammatory phenotyping in patients with asthma.