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

The Pattern of Sensitization Influences Exhaled and Nasal Nitric Oxide Levels in Young Adults

Nitric oxide (NO) from upper (nasal NO, nNO) or lower airways (fractional exhaled NO, FeNO) is considered a surrogate marker for Th2-type inflammation, which is influenced by atopy. The aim of this study was to analyze nNO and FeNO in regard to qualitative and quantitative aspects of sensitization. We evaluated 244 non-smoking young adults. All of them were first-year students recruited for a longitudinal study. An inhalation allergy screening tool was used for atopy definition (specific immunoglobulin E (sIgE) to sx1 ≥ 0.35 kU/L), and also sIgE response to three inhalant perennial allergens, house dust mite (HDM, d1), cat (e1), and dog (e5), was determined in the non-pollen season. With respect to sx1, 100 subjects could be classified as atopic. Sensitization to one, two, or three perennial allergens could be demonstrated in 46, 10, and 16 students, respectively. The subjects with positive IgE response to sx1, but not sensitized to HDM, cat, and/or dog, had FeNO levels comparable to those of non-atopic subjects (13.5 vs. 13.0 ppb, respectively; p = 0.485). These levels were significantly lower compared to atopic subjects being sensitized to any perennial allergen (19.0 ppb; p = 0.0003). After grouping the atopic subjects for perennial sensitization patterns, significantly higher FeNO could be detected in subjects with poly-sensitization (n = 26; 26.0 ppb) compared to the mono-sensitized ones (n = 46; 18.0 ppb; p = 0.023). Regarding nNO, no differences could be observed. Applying a two-way ANOVA, we could reveal a significant correlation of specific HDM-IgE CAP-class with FeNO (p < 0.0001) and nNO levels (p = 0.007). Finally, a significant relationship was found between nNO and FeNO for the whole cohort (p < 0.0001). In summary, our findings support the argument that atopy and perennial sensitization should be considered for the interpretation of NO.

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.

Role of exhaled nitric oxide as a predictor of atopy

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Bronchial hyperresponsiveness in an adult population in Helsinki: decreased FEV1 , the main determinant

Introduction

Bronchial hyperresponsiveness (BHR) elevates the risk for development of respiratory symptoms and accelerates the decline in forced expiratory volume in the first second (FEV₁). We thus aimed to assess the prevalence, determinants and quantity of BHR in Helsinki.

Objectives

This study involved 292 randomly selected subjects age 26–66 years, women comprising 58%.

Methods

Following a structured interview, a spirometry, a bronchodilation test, and a skin-prick test, we assessed a bronchial challenge test with inhaled histamine using a dosimetric tidal breathing method. Results included the provocative dose inducing a decrease in FEV₁ by 15% (PD₁₅FEV₁) and the dose-response slope. For statistical risk factor-analyses, the severity of BHR was considered; PD₁₅ values ≤1.6 mg (BHR) and ≤0.4 mg [moderate or severe BHR (BHR_ms)] served as cut-off levels.

Results

BHR presented in 21.2% and BHR_ms in 6.2% of the subjects. FEV₁ < 80% of predicted [odds ratio (OR) 4.09], airway obstruction (FEV₁/forced vital capacity < 88% of predicted) (OR 4.33) and history of respiratory infection at age <5 (OR 2.65) yielded an increased risk for BHR as ORs in multivariate analysis. For BHR_ms, the determinants were decreased FEV₁ below 80% of predicted (OR 27.18) and airway obstruction (OR 6.16). Respiratory symptoms and asthma medication showed a significant association with BHR.

Conclusions

Of the adult population of Helsinki, 21% showed BHR to inhaled histamine. The main determinants were decreased FEV₁ and airway obstruction. Quantitative assessment of BHR by different cut-off levels provides a tool for characterization of phenotypes of airway disorders in epidemiologic and clinical studies.

Please cite this paper as: Juusela M, Pallasaho P, Sarna S, Piirilä P, Lundbäck B and Sovijärvi A. Bronchial hyperresponsiveness in an adult population in Helsinki: decreased FEV₁, the main determinant. Clin Respir J 2013; 7: 34–44.

Increase in exhaled nitric oxide is associated with bronchial hyperresponsiveness among apprentices

RATIONALE

Airway inflammation is a hallmark of asthma. Several studies have validated the use of the fractional concentration of exhaled nitric oxide (Fe(NO)) as a surrogate marker of airway inflammation in asthma.

OBJECTIVES

We examined how the change in Fe(NO) levels, since the beginning of occupational exposure, could be associated with the incidence of bronchial hyperresponsiveness (BHR) among baker, pastry maker, and hairdresser apprentices during their 2-year training.

METHODS

A standardized questionnaire was administered; skin prick tests for common and specific occupational allergens were done; methacholine challenge and measurement of Fe(NO) were performed 6, 12, and 15 months after the first examination.

MEASUREMENTS AND MAIN RESULTS

Of 441 apprentices initially included, 351 completed the study. The increase in Fe(NO), since the beginning of exposure, was associated with the incidence of BHR (odds ratio, 2.00 [95% confidence interval, 1.21-3.32] per unit increase in log parts per billion) both in atopic and nonatopic subjects. The average increase in Fe(NO) was similar in atopic and nonatopic subjects and was unrelated to past or current smoking habits, sex, or training track. Atopy in bakers/pastry makers and sensitization to alkaline persulfates in hairdressers were also independently associated with the incidence of BHR. BHR occurred sooner among bakers/pastry makers than among hairdressers, but its incidence leveled off later.

CONCLUSIONS

Our results suggest that measurement of Fe(NO), a simple and reproducible test, could be useful in the screening of BHR in workers newly exposed to agents known to cause occupational asthma.