Is the allergen-inhalation challenge predictive of the severity of seasonal asthmatic exacerbations?

Aeroallergen sensitization correlates with PC(20) and exhaled nitric oxide in subjects with mild-to-moderate asthma

BACKGROUND

Aeroallergen sensitization in adult asthmatic patients from a wide geographic area has not been correlated with patients' characteristics, markers of airways inflammation, and lung function.

OBJECTIVE

We assessed data obtained from the Asthma Clinical Research Network trials to determine the relationship of aeroallergen sensitization to age, sex, ethnicity, and markers of inflammation and airways function.

METHODS

Skin testing (14 epicutaneous) was performed on 1338 subjects with objectively diagnosed mild-to-moderate asthma from 11 Asthma Clinical Research Network studies. Skin testing used identical techniques and a quality assurance program to ensure uniformity across centers.

RESULTS

Ninety-five percent of the subjects had at least 1 positive skin test response. Of these, 14% had positive reactions to 1 or 2 allergens and 81% had positive reactions to 3 or more allergens, and 2% of subjects reacted only to seasonal allergens, 26% only to perennial allergens, and 67% to both. Increasing IgE and exhaled nitric oxide values, decreasing PC(20) values, and minority ethnicity significantly correlated with the number of positive skin test responses. Subjects with late-onset asthma were less likely to be sensitized; nonetheless, 89% of subjects older than 60 years had positive responses.

CONCLUSION

Ninety-five percent of patients with mild-to-moderate asthma might have an allergic component. Age does not significantly affect aeroallergen sensitization, but the pattern of allergic sensitization varies with ethnicity and geography. Measures used to characterize asthma, such as IgE, exhaled nitric oxide, and PC(20) values, are correlated with aeroallergen sensitization.

Characteristics of patients with seasonal allergic rhinitis and concomitant asthma

BACKGROUND

Allergic rhinitis and asthma often co-exist and appear to produce a continuum of airway disease, but whether the clinical characteristics of asthma in patients with seasonal rhinitis differ from those of persistent asthma has not been examined.

OBJECTIVE

The aim of this retrospective study was to characterize the clinical features of patients with seasonal allergic rhinitis with concomitant asthma and to compare them with those in patients with persistent asthma.

METHODS

The patient populations for this study were derived from nine prospective, placebo-controlled planned clinical trials of similar design. Six studies (958 patients) enrolled patients with seasonal allergic rhinitis and concomitant asthma; three (607 patients) involved patients with persistent asthma. In all studies, patients were excluded from oral corticosteroid therapy in the preceding 3 months, and from inhaled corticosteroids in the preceding month.

RESULTS

Patients with seasonal rhinitis and asthma had a significantly (P<0.001) higher total asthma symptom score than those with persistent asthma. In particular, cough was three times more severe. The need for beta(2)-agonist as a rescue medication and the ratio of forced expiratory volume in 1 s/forced vital capacity (FVC) were similar in the two groups whereas forced expiratory fraction 25-75%/FVC was significantly (P<0.02) reduced in the persistent asthmatics. Asthma and nasal symptom severity scores were correlated in patients with seasonal rhinitis and asthma (P<0.0001).

CONCLUSIONS

Patients with seasonal allergic rhinitis and concomitant asthma appear to differ from those with persistent asthma. A prospective study should be designed to discover whether patients with seasonal rhinitis and asthma may represent a distinct nosological entity, 'allergic airway disease'.

Threshold levels of purified natural Bos d 2 for inducing bronchial airway response in asthmatic patients

BACKGROUND

Provocation tests are invaluable in establishing threshold levels and a causal relationship between atopic asthma and a certain allergen source, especially in relation to work-associated exposure. Purified major allergens open possibilities for a more accurate assessment of sensitization.

OBJECTIVE

To determine the threshold dose of purified major bovine dander allergen Bos d 2 in bronchial provocation in comparison with the standard allergen and a set of other parameters of allergy.

METHOD

Nine consecutive patients referred to hospital for confirming the bovine origin of their occupational asthma were subjected to bronchial provocation tests with purified natural Bos d 2 and a standard bovine dander allergen. Additional tests included bronchial histamine challenge, measurements of total IgE, specific IgE antibody determinations and skin prick tests (SPT) with both allergens.

RESULTS

In the provocation tests with Bos d 2, a 15% decrease in the forced expiratory volume in 1 s (FEV1) and/or peak expiratory flow (PEF) values in eight out of nine patients confirmed the predominant role of Bos d 2 in the sensitization. The threshold dose of Bos d 2 varied from 0.1 microg to > 100 microg (median +/- median absolute deviation = 4.5 +/- 3.9 microg). A positive SPT was induced by a median dose of 13.9 +/- 9.8 microg of Bos d 2. Bronchial response to histamine and IgE antibodies against Bos d 2 showed the highest correlations to the provocations results.

CONCLUSIONS

The efficacy of Bos d 2 in bronchial provocation in patients with occupational cattle-associated asthma was confirmed and the range of the threshold level was determined. There were individual variations, but the response in provocation remains the reference method for identification of the cause of occupational atopic asthma. SPT and the measurement of specific IgE antibodies, preferably with purified or recombinant major allergens, increase the accuracy of the diagnosis.

Mild exacerbations and eosinophilic inflammation in patients with stable, well-controlled asthma after 1 year of follow-up

OBJECTIVES

To determine the time to exacerbation and probability of a mild exacerbation of asthma, and the impact of eosinophilic inflammation on these parameters in patients with stable, well-controlled asthma.

PATIENTS AND METHODS

A cohort of 31 patients with stable, well-controlled asthma receiving inhaled steroid treatment regularly were followed up for 1 year or until a mild exacerbation occurred. Mild exacerbation was defined as symptoms of asthma lasting > 48 h with a fall in peak expiratory flow > 20%. FEV(1), provocative concentration of methacholine causing a 20% fall in FEV(1), eosinophil count, and eosinophilic cationic protein (ECP) levels in blood and in sputum were measured at the first visit and every 2 months.

RESULTS

At baseline, the mean (SD) eosinophil count was 0.39 x 10(9)/L (0.21 x 10(9)/L) in blood and 13% (14%) in sputum; ECP was 30 microg/L (28 microg/L) in blood and 75 microg/L (85 microg/L) in sputum. Thirteen subjects experienced a mild exacerbation during the 1-year follow-up period. The mean time to mild exacerbation was 293 days (95% confidence interval [CI], 248 to 337 days), and the cumulative probability of not experiencing a mild exacerbation in 1 year was 49% (95% CI, 39 to 59%). An increased risk of mild exacerbation was associated with blood eosinophil count > 0.4 x 10(9)/L (relative risk 4.5; 95% CI of relative risk, 1.8 to 38.0), blood ECP > 20 microg/L (relative risk, 2.1; 95% CI of relative risk, 1.0 to 9.2), and sputum ECP > 40 microg/L (relative risk, 2.5; 95% CI of relative risk, 1.2 to 11.2), but was unassociated with other variables.

CONCLUSIONS

Patient with stable, well-controlled asthma are at risk of mild exacerbation during 1 year of follow-up despite regular inhaled steroid treatment. Eosinophilic inflammation expressed as eosinophil count and ECP is associated with higher risk of mild exacerbation.

The association of sensitization to inhalant allergens with allergy symptoms: the influence of bronchial hyperresponsiveness and blood eosinophil count

BACKGROUND

We investigated whether the association of allergy symptoms with sensitization to inhalant allergens depends on bronchial hyperresponsiveness, blood eosinophil count, or the degree and nature of sensitization.

METHODS

Data on asthma and rhino-conjunctivitis symptoms were obtained from 1904 subjects from a random sample of the Dutch population, aged 20-70 years by the ECRHS questionnaire. Total IgE and specific IgE to four inhalant allergens were measured using CAP System. Bronchial hyperresponsiveness (BHR) was defined as PD20 </= 2 mg methacholine and 'high eosinophil count' as an eosinophil count in the highest quartile.

RESULTS

Forty-three percent of the subjects with specific IgE to inhalant allergens was asymptomatic. These subjects had a lower degree of sensitization than symptomatic sensitized subjects and had 'normal' prevalences of BHR and 'high eosinophil count'. Logistic regression showed that the presence of BHR increased the risk of having symptoms for subjects who were sensitized to indoor allergens. Low levels of specific IgE to indoor allergens were only associated with symptoms when BHR was present. Sensitization to outdoor allergens was associated with symptoms at all levels of specific IgE, independently of BHR or eosinophils.

CONCLUSION

Our epidemiological data suggest that whether low levels of specific IgE to indoor allergens lead to allergic symptoms is probably determined by the concurrent existence of inflammation of the airways.

Relationship between increased airway responsiveness and asthma severity in the childhood asthma management program

The relationship between increased airway responsiveness and asthma severity in children is unclear. The Childhood Asthma Management Program (CAMP) with 1,041 children with mild to moderate asthma offers an opportunity to relate the concentration of methacholine that causes a 20% fall in FEV(1) (PC(20)) to level of lung function, occurrence of respiratory symptoms, duration of disease, and assessment of severity by clinical staff. Decreasing PC(20) was found to be associated with lower levels of lung function (prebronchodilator percent predicted FEV(1): r = 0.29, beta = 3.5, p < 0.001), the occurrence of chronic asthma symptoms, persistent wheezing (odds ratio [OR] = 1.66, p < 0.001), subjective clinical staff assessment of asthma severity (p < 0.001), and longer duration of asthma (r = -0.11, beta = -0.20, p < 0.002). These data provide evidence that the degree of airway responsiveness is linked to disease severity in children with mild to moderate asthma.

Relationship of cellular transmigration and airway response after allergen challenge

We examined the relationship between eosinophil migration into the bronchoalveolar space and change in FEV(1) after endobronchial allergen challenge (EBAC) in atopic asthmatic (AA) and atopic nonasthmatic (ANA) subjects. The purpose of this study was to obtain continuous, intrasubject controlled assessment of the relationship between cell migration in control and allergen-challenged segments in the same individuals over 96 h. In AA subjects, the eosinophil (Eos) count in the bronchoalveolar lavage fluid (BALF) increased from a baseline of 7,896 +/- 3,865 to 416,476 +/- 231,012 Eos/ml by 72 h (p = 0.001) in the challenged segment post-EBAC. For ANA subjects, the postsegmental challenge count was 29,874 +/- 474 Eos/ml (p = 0.03 versus baseline and p < 0.05 AA peak versus ANA peak). In both groups, there was a comparable decrease in peripheral blood eosinophil count beginning 5 h after challenge, which resolved at 24 h. In AA subjects, 416,476 +/- 231,012 Eos/ml was obtained from the allergen-challenged segment and 23,522 +/- 8,298 Eos/ml was obtained from the sham-challenged segment (p < 0.001) at 72 h. In contrast, there was no difference in the Eos count obtained from the BALF between the antigen- and sham-challenged segments of ANA subjects. We also found that increased airway neutrophils were present in equal numbers in allergen-challenged and sham-challenged segments in both AA and ANA subjects. We conclude that augmented eosinophil migration after EBAC is a characteristic of atopic asthma and is not present in atopic subjects who do not have asthma. We find that BAL eosinophilia in ANA patients as well as neutrophilia in both ANA and AA subjects are nonspecific consequences of bronchoscopy. Finally, we find no relationship between specific airway eosinophil migration into the BALF and FEV(1) < 72 h after challenge; however, at 96 h, there is a substantial decrease in FEV(1) that accompanies BALF eosinophilia.