Assessment of inhaled BDP-dose dependency of exhaled nitric oxide and local and serum eosinophilic markers in steroids-naive nonatopic asthmatics

Correlation between fractional exhaled nitric oxide and Asthma Control Test score and spirometry parameters in on-treatment-asthmatics in Ho Chi Minh City

Background

Although fractional exhaled nitric oxide (FeNO) is a reliable and easily applied marker of airway inflammation in asthma, the relationship between FeNO and indicators of asthma control [Asthma Control Test (ACT) score] and/or severity (spirometry parameters) remains unclear. This study aims to determine possible correlations between FeNO and ACT score; and between FeNO and spirometry parameters.

Methods

A cross-sectional study with convenience sampling was conducted among ambulatory patients in the Asthma & COPD clinic at the University Medical Center, Ho Chi Minh City from March 2016 to March 2017. Using measurement of FeNO, the ACT questionnaire and a spirometry test, correlations were determined between FeNO and the ACT score and spirometry parameters.

Results

Four hundred and ten asthmatic patients (mean age 42 years; 65% female) were included and analyzed; their mean time since onset of asthma was 9.5 years. All patients were treated following step 2 to 4 of GINA guidelines. Mean (SD) FeNO was 29.5 (24.4) parts per billion (ppb) and mean (SD) ACT score was 20.5 (40). A significant difference in FeNO values was found among the three groups with different asthma control levels categorized according to the ACT score (P=0.001) but was not found among the three groups with different asthma treatment levels (P=0.425). FeNO was significantly inversely correlated with the ACT score (Spearman’s r =−0.224, P<0.001) and with spirometry parameters indicate airway obstruction such as predicted FEV1, FEV1/FVC, predicted PEF and predicted FEF25–75% with Spearman’s r were −0.187; −0.143; −0.091 and −0.195, respectively (all P<0.05), whereas no correlation between FeNO and FVC—an indicator of airway restriction—was found.

Conclusions

In these asthmatic patients in Vietnam, an inverse correlation was found between FeNO and the ACT score and between FeNO and spirometry indicators of airway obstruction. Therefore, FeNO may be a useful tool in asthma management.

Pharmacodynamic monitoring using biomarkers to individualize pharmacotherapy

Drug doses are often titrated upon their clinical effects (e.g., blood pressure). Unfortunately, for many drugs there is no direct, clinical read-out to estimate dose adequateness. Alternatively, drug dosing is based on the maximum tolerated dose approach or therapeutic drug monitoring. However, the concentration-response curves may be flattened or bell-shaped as suggested for some ‘biologicals’. Together, these aspects raise the question why drug dosing is not individualized by pharmacodynamic monitoring. Evaluating the effects of drugs at their pharmacological target or meaningful biomarkers might indicate nonresponders, objectively quantify the maximum molecular effect and thus restrict overdose and underdosing. This review outlines the theory and biological or technical prerequisites for biomarker-based pharmacodynamic monitoring, and highlights selected examples from different fields of clinical medicine.

The absence of serum IgE antibodies indicates non-type 2 disease in young asthmatics

BACKGROUND

Atopic asthma is associated with elevated type-2 biomarkers such as fraction of exhaled nitric oxide (FeNO) and blood eosinophil (B-Eos) count. However, increased type 2 markers have also been reported in traditionally defined non-atopic asthma.

OBJECTIVE

To determine a clinically useful level of IgE sensitization for ruling out type 2 asthma.

METHODS

Asthmatics (N = 408; age 10-35 years) were analysed using the multi-allergen tests Phadiatop and fx5 (ImmunoCAP). Subjects were grouped based on IgE-antibody concentrations: ≥0.35 kU_A /L for at least one test (n = 326) or <0.35 kU_A /L for both tests (n = 82). Τhe latter group was subsequently divided into 2 groups: IgE 0.10-0.34 kU_A /L (n = 34) and IgE < 0.10 kU_A /L (n = 48). The relationships between type 2 biomarkers, and inadequate asthma control (ACT < 20), reduced lung function (FEV₁  < 80%), recent asthma attacks and airway hyperresponsiveness (AHR) to methacholine were determined.

RESULTS

In univariate analyses, at least one type 2 marker related to each asthma outcome in subjects with IgE ≥0.35 kU_A /L. In subjects with IgE 0.10-0.34 kU_A /L, elevated FeNO related to reduced lung function (P = .008) and B-Eos to AHR (P = .03). No associations were found in subjects with IgE < 0.10 kU_A /L. In multivariate analysis, a relationship between FeNO and reduced lung function remained in subjects with IgE < 0.35 kU_A /L (P = .03).

CONCLUSION AND CLINICAL RELEVANCE

Clinically relevant elevation of type 2 biomarkers was seen in young asthmatics with IgE antibodies <0.35 kU_A /L, but not those with IgE < 0.10 kU_A /L. It seems possible to define non-type 2 asthma through sensitive IgE-antibody measurement.

Airway gas exchange and exhaled biomarkers

During inspiration and expiration, gases traverse the conducting airways as they are transported between the environment and the alveolar region of the lungs. The term "conducting" airways is used broadly as the airway tree is thought largely to provide a conduit for the respiratory gases, oxygen and carbon dioxide. However, despite a significantly smaller surface area, and thicker barrier separating the gas phase from the blood when compared to the alveolar region, the airway tree can participate in gas exchange under special conditions such as high water solubility, high chemical reactivity, or production of the gas within the airway wall tissue. While these conditions do not apply to the respiratory gases, other gases demonstrate substantial exchange of the airways and are of particular importance to the inflammatory response of the lungs, the medical-legal field, occupational health, metabolic disorders, or protection of the delicate alveolar membrane. Given the significant structural differences between the airways and the alveolar region, the physical determinants that control airway gas exchange are unique and require different models (both experimental and mathematical) to explore. Our improved physiological understanding of airway gas exchange combined with improved analytical methods to detect trace compounds in the exhaled breath provides future opportunities to develop new exhaled biomarkers that are characteristic of pulmonary and systemic conditions.

Is low dose inhaled corticosteroid therapy as effective for inflammation and remodeling in asthma? A randomized, parallel group study

Background

While most of the clinical benefits of inhaled corticosteroid (ICS) therapy may occur at low doses, results of dose-ranging studies are inconsistent. Although symptom/lung function response to low and high dose ICS medication is comparable, it is uncertain whether low dose ICSs are as effective as high dose in the treatment of inflammation and remodeling.

Methods

22 mild or moderate asthmatic adult subjects (corticosteroid free for > 2 months) participated in a randomized, parallel group study to compare effects of fluticasone propionate (FP) 200 mcg/day and 1000 mcg/day. Alveolar macrophage (AM)-derived cytokines and basement membrane thickness (BMT) were measured at baseline and after 7 weeks treatment while symptoms, spirometry, exhaled nitric oxide (eNO) and airway hyperresponsiveness (AHR) to mannitol at baseline and 6 weeks.

Results

FP improved spirometry, eNO, symptoms and AHR with no difference between low and high dose FP. Both high and low dose FP reduced GM-CSF, TNF-alpha and IL-1ra, with no change in BMT and with no differences between low and high dose FP.

Conclusions

200 μg/day of FP was as effective as 1000 μg/day in improving asthma control, airway inflammation, lung function and AHR in adults in the short term. Future studies should examine potential differential effects between low and high dose combination therapy (ICS/long acting beta agonist) on inflammation and airway remodeling over longer treatment periods.

Comparison of eNO and histamine hyperresponsiveness in diagnosing asthma in new referrals

The mainstay of the diagnosis of asthma is the presence of reversible airway obstruction. Exhaled NO levels are increased in asthma, in close relationship with the amount of airway inflammation, and may be used for monitoring the disease and adjusting therapy. In this study we investigated the role of eNO as a diagnostic for asthma, compared with the FEV1-reversibility and the PC20 (20% decrease of the FEV1 in the bronchial histamine provocation test), in two independent centers, on an unselected population. ENO measurements were performed with chemoluminesence technique in one center and with an electrochemical device in the other. Only after correction for so-called nuisance factors (allergy, use of inhaled steroids, recent infection, smoking, sex and the use of nitrate food) the eNO appeared as a diagnostic with equal power as the FEV1-reversibility and the PC20. Therefore, screening for asthma in our study population, with the eNO measurement, is a simple, fast and safe strategy.

Time-dependent effects of inhaled corticosteroids on lung function, bronchial hyperresponsiveness, and airway inflammation in asthma

BACKGROUND

Exhaled nitric oxide (F(ENO)) and exhaled breath condensate (EBC) are noninvasive markers that directly measure airway inflammation and may potentially be useful in assessing asthma control and response to therapy.

OBJECTIVE

To examine the time-dependent effects of inhaled corticosteroids on F(ENO) and EBC markers concomitantly with lung function and bronchial hyperresponsiveness.

METHODS

Eleven steroid-naive adults with mild-to-moderate persistent asthma were treated with mometasone furoate dry powder inhaler, 400 microg/d, for 8 weeks, followed by a 4-week washout. Forced expiratory volume in 1 second (FEV1), the concentration of methacholine calculated to cause a 20% decline in FEV1 (PC20), F(ENO), EBC pH, and EBC nitrite measurements before, during, and after treatment were analyzed and compared.

RESULTS

The mean (SEM) FEV1 increased from 3.01 (0.13) L (82% predicted) to 3.24 (0.18) L (87% predicted) by week 8 (P < .05). The PC20 level increased from 1.28 (0.31) mg/mL to 2.99 (0.51) mg/mL by treatment week 8 (P < .05) and remained relatively stable through washout week 4 (P < .05). The F(ENO) level decreased from 31.1 (4.1) ppb to 20.6 (4.5) ppb by treatment week 1 (P < .01), remained low through treatment week 8 (P < .01), then trended back to the baseline level by washout week 1 (P < .01). The median EBC pH increased from 7.81 (interquartile range, 7.49-8.09) to 8.02 (interquartile range, 7.87-8.12) by treatment week 4, but did not achieve statistical significance. The EBC nitrite level decreased from 17.6 (1.6) microM to 9.3 (0.9) microM by treatment week 8 (P < .01), and remained low throughout washout week 4 (P < .05). There was a negative correlation between F(ENO) and PC20 (Spearman rank correlation coefficient = -0.50, P < .001).

CONCLUSION

The F(ENO) level responded the earliest to treatment and withdrawal of inhaled corticosteroids, whereas changes in EBC markers were delayed but more sustained.

Equally elevated concentrations of exhaled nitric oxide in nonatopic and low-sensitized atopic asthmatics

BACKGROUND

Some studies show concentrations of exhaled nitric oxide (FENO) in nonatopic asthma and in healthy subjects to be similar, but include asthmatics on inhaled steroids, which is likely to interfere with the results.

AIM

Comparison of FENO between nonatopic asthmatics, low-sensitized and high-sensitized atopic asthmatics, and healthy controls.

METHODS

We studied 85 non-smoking, steroid-naive young men with recently diagnosed symptomatic asthma and 10 healthy controls. FENO was measured according to European Respiratory Society Guidelines. In skin prick tests of 13 common aeroallergens, subjects with a total sum of prick wheals 3-10mm were regarded as low-sensitized and those with >10mm, as high-sensitized. Flow-volume spirometry, standardized histamine challenge, and an exercise test were also carried out.

RESULTS

Prick tests revealed 14 subjects to be nonatopic and 71 atopic. In high-sensitized subjects with atopic asthma, the FENO median (25-75 quartiles) was significantly higher, 34.9 (21.3-53.8) parts per billion (ppb), than in subjects with nonatopic asthma, 15.2 (9.7-24.7)ppb (p<0.001), both being significantly higher than in healthy controls, 6.6 (5.2-8.5)ppb (p<0.001). FENO levels were similar in nonatopic and in low-sensitized atopic asthmatics, with no difference between them in bronchial responsiveness to histamine and exercise.

CONCLUSION

Among steroid-naive young male asthmatics, FENO was equally elevated in nonatopic asthma and in low-sensitized atopic asthma but lower than in those with high-sensitized atopic asthma. These differences in FENO between asthma groups parallel the differences in airway function disturbance in terms of responsiveness to histamine or exercise.

Partitioned exhaled nitric oxide to non-invasively assess asthma

Asthma is a chronic inflammatory disease of the lungs, characterized by airway hyperresponsiveness. Chronic repetitive bouts of acute inflammation lead to airway wall remodeling and possibly the sequelae of fixed airflow obstruction. Nitric oxide (NO) is a reactive molecule synthesized by NO synthases (NOS). NOS are expressed by cells within the airway wall and functionally, two NOS isoforms exist: constitutive and inducible. In asthma, the inducible isoform is over expressed, leading to increased production of NO, which diffuses into the airway lumen, where it can be detected in the exhaled breath. The exhaled NO signal can be partitioned into airway and alveolar components by measuring exhaled NO at multiple flows and applying mathematical models of pulmonary NO dynamics. The airway NO flux and alveolar NO concentration can be elevated in adults and children with asthma and have been correlated with markers of airway inflammation and airflow obstruction in cross-sectional studies. Longitudinal studies which specifically address the clinical potential of partitioning exhaled NO for diagnosis, managing therapy, and predicting exacerbation are needed.

Exhaled nitric oxide predicts airway hyper-responsiveness to hypertonic saline in children that wheeze

BACKGROUND

Exhaled nitric oxide (eNO) has shown good validity for the assessment of airway inflammation in asthmatic children. In large-scale epidemiological studies, this method would be preferred above airway challenge tests, because it is a quick and easy applicable tool.

OBJECTIVE

In this study, we aimed to assess the discriminatory capacity of eNO, and prechallenge FEV1 for airway hyper-responsiveness (AHR) in 8-13-year old schoolchildren.

MATERIALS AND METHODS

Parents completed the ISAAC questionnaire, and children were tested for atopy, AHR to hypertonic (4.5%) saline (HS), and eNO. Diagnostic value was assessed by the area under the receiver operating curves (ROC), and calculation of positive and negative predicted values at different cut-off points for eNO and prechallenge FEV1.

RESULTS

Areas under the ROC-curves of AHR were 0.65 for eNO and 0.62 for FEV1. Values increased to 0.71 and respectively 0.75 for a combined occurrence of AHR and current wheeze. Highest sensitivity and specificity were obtained at a cut-off value of 43 ppb for eNO and 103% predicted for FEV1. At these cut-off values, the positive predictive values for the presence of AHR in symptomatic children were respectively 83% (eNO) and 33% (FEV1), and negative predictive values in asymptomatic children were, respectively, 90 (eNO) and 80% (FEV1).

CONCLUSION

Exhaled nitric oxide is a valid screening tool for AHR to HS in children that present with current wheeze, and it outperforms FEV1 as a predictor of AHR.

Pulmonary effects of indoor- and outdoor-generated particles in children with asthma

Most particulate matter (PM) health effects studies use outdoor (ambient) PM as a surrogate for personal exposure. However, people spend most of their time indoors exposed to a combination of indoor-generated particles and ambient particles that have infiltrated. Thus, it is important to investigate the differential health effects of indoor- and ambient-generated particles. We combined our recently adapted recursive model and a predictive model for estimating infiltration efficiency to separate personal exposure (E) to PM2.5 (PM with aerodynamic diameter < or = 2.5 microm) into its indoor-generated (Eig) and ambient-generated (Eag) components for 19 children with asthma. We then compared Eig and Eag to changes in exhaled nitric oxide (eNO), a marker of airway inflammation. Based on the recursive model with a sample size of eight children, Eag was marginally associated with increases in eNO [5.6 ppb per 10-microg/m3 increase in PM2.5; 95% confidence interval (CI), -0.6 to 11.9; p = 0.08]. Eig was not associated with eNO (-0.19 ppb change per 10 microg/m3). Our predictive model allowed us to estimate Eag and Eig for all 19 children. For those combined estimates, only Eag was significantly associated with an increase in eNO (Eag: 5.0 ppb per 10-microg/m3 increase in PM2.5; 95% CI, 0.3 to 9.7; p = 0.04; Eig: 3.3 ppb per 10-microg/m3 increase in PM2.5; 95% CI, -1.1 to 7.7; p = 0.15). Effects were seen only in children who were not using corticosteroid therapy. We conclude that the ambient-generated component of PM2.5 exposure is consistently associated with increases in eNO and the indoor-generated component is less strongly associated with eNO.