An update on pollen and fungal spore aerobiology

Changes in climate are altering pollen distribution. Predictive modeling can be used to forecast long- and short-term changes in pollen concentrations. Increasing evidence confirms the presence of pollen allergens on small, respirable particles in the air, explaining the occurrence of pollen-season increases in asthma. Like pollens, aboveground indoor fungal aerosols primarily reflect outdoor concentrations. Basement spore concentrations might be higher and reflective of local sources. Fungal presence in the indoor or outdoor air can be monitored on an area basis or with personal monitors. The samples can be analyzed by means of microscopy, culture, DNA probes, HPLC, or immunodetection. Total fungal biomass can be estimated on the basis of measurements of ergosterol or glucan in environmental samples. Unfortunately, there are no generally accepted standards for interpretation of fungal levels in indoor or outdoor air. At present, the best approach to indoor fungal control is moisture control in the indoor environment. This will essentially prevent fungal growth, except from extraordinary events.     

Combined effects of aerobiological pollutants, chemical pollutants and meteorological conditions on asthma admissions and A & E attendances in Derbyshire UK, 1993–96.

BACKGROUND: The effect of outdoor aeroallergen exposure in asthma may be enhanced by air pollutants, including ozone, nitrogen dioxide and particulates, and by certain weather conditions. It is not yet established whether these interactions are important in determining asthma morbidity at the population level. OBJECTIVE: We have investigated the joint effects of aeroallergens, rainfall, thunderstorms and outdoor air pollutants on daily asthma admissions and Accident and Emergency (A & E) attendance using routinely collected data between 1993 and 1996 from Derby in central England. METHODS: Daily counts during the aeroallergen season of grass and birch pollen, basidiospores, Didymella, Alternaria and Cladosporium, maximum 1 hour ozone and nitrogen dioxide and daily average black smoke measurements, all made in the vicinity of the city centre, were categorized in tertiles. Rainfall was classified as dry, light ( 2 mm). The modifying effect of outdoor pollutant levels, and rainfall or the occurrence of a thunderstorm, upon the effects of individual aeroallergens on asthma admissions and A & E attendance were investigated by fitting appropriate interactions in log linear autoregression models with adjustment for potential confounders. RESULTS: We found a significant interaction between the effects of grass pollen and weather conditions upon A & E attendance, such that the increase with grass pollen count was most marked on days of light rainfall (adjusted rate ratio for >/= 50 vs < 10 grains/m3 at lag 2 days = 2.1, 95% CI 1.4, 3.3). Asthma admissions increased with Cladosporium count. We found no statistically significant interactions between effects of any individual aeroallergen and outdoor air pollutant upon either measure of asthma morbidity. CONCLUSIONS: Rainfall and thunderstorms are important effect modifiers in the relation between grass pollen and measures of acute asthma morbidity. Interactions between ambient levels of aeroallergens and chemical pollutants in the Derby area do not play a major role in determining asthma admissions and A & E attendance.     

Analysis of the relationships between environmental factors (aeroallergens, air pollution, and weather) and asthma emergency admissions to a hospital in Mexico City

There have been several studies of the relationships between environmental factors, particularly air pollution, and attacks of asthma. Most of these studies have ignored the potential confounding effects of aeroallergens such as pollens and fungal spores. We report a statistical analysis of the relationships between emergency admissions for asthma to a hospital in Mexico City and daily average airborne concentrations of pollen, fungal spores, air pollutants (O₃, NO₃, SO₃. and particulates) and weather factors. Asthma admissions had a seasonal pattern with more during the wet season (May-October) than the dry season (November-April). There were few statistical associations between asthma admissions and air pollutants for the three age groups studied (children under 15 years, adults, and seniors [adults over 59 years]) in either season. Grass pollen was associated with child and adult admissions for both the wet and dry seasons, and fungal spores were associated with child admissions during both the wet and dry seasons. The analysis was done with environmental data averaged over the day of admission and the 2 previous days. Our results suggest that aeroallergens may be statistically associated more strongly with asthma hospital admissions than air pollutants and may act as confounding factors in epidemiologic studies.     

The role of symptomatic colds in asthma exacerbations: Influence of outdoor allergens and air pollutants.

BACKGROUND: Both air pollutants and respiratory viral infections have been recognized to be important triggers of asthma exacerbations, but the possible interaction of these has not been assessed in an epidemiologic study. OBJECTIVE: In this study, we aimed to assess the possible associations of symptomatic colds with outdoor allergens and air pollutants in exacerbating asthma. METHODS: A total of 57 adults and children with asthma participated in a 1-year study in Vancouver, British Columbia. Diary cards recording symptoms of asthma and colds, medication usage, and peak expiratory flow rates were completed twice daily. Outdoor air pollutant levels and levels of pollen and fungal spores were measured. Levels were examined for associations with exacerbations of asthma with symptoms of a cold, as compared with asthma exacerbations with no cold symptoms and colds in the absence of asthma exacerbations. RESULTS: Of 130 asthma exacerbations, 47% were associated with cold symptoms (accounting for 44% of episodes of colds). Asthma exacerbations with colds were associated with higher levels of sulfur dioxide, and nitric oxide during March to November in comparison with asthma exacerbations without cold symptoms (P <.018). Cold-symptom days overall were more common in winter and were significantly associated with lower temperatures, lower ozone levels, and higher sulfur dioxide, nitrogen dioxide, nitrogen oxide (NO and NO(x)), and carbon monoxide levels. CONCLUSIONS: Asthma exacerbations are commonly associated with cold symptoms. These episodes are associated with higher levels of sulfur dioxide and nitrogen oxides from March to November in comparison with asthma exacerbations without cold symptoms.     

Respiratory hospital admissions were associated with ambient airborne pollen in Darwin, Australia, 2004–2005

BACKGROUND: Although the role of pollen and fungus in specific allergic disorders has been well established, the public health impacts of ambient concentrations of airborne pollen and fungal spores; the shapes of concentration-response relationships; and the relative effects of different taxa are gaps in current knowledge. OBJECTIVE: To investigate associations between daily average ambient pollen and fungal spore concentrations with hospital admissions for total respiratory diseases; asthma; chronic obstructive pulmonary disease (COPD); and respiratory infections in Darwin, Australia, during the period from April 2004 to November 2005. METHODS: We assessed these relationships in a two-stage modelling approach designed to quantify potential non-linear relationships. First, generalized additive models determined the shapes of concentration-response relationships. Second, linear associations were examined using generalized linear models. Non-linear relationships were analysed by categorizing pollen and fungal spore concentrations based on their distributions. RESULTS: Positive linear associations were found between total pollen concentrations and hospital admissions for total respiratory diseases and COPD. While our exploratory first-stage analysis suggested non-linear relationships for total pollen with asthma and respiratory infections, no convincing evidence for these relationships was found in the second-stage analysis. When individual taxa were investigated, associations were the strongest in relation to Myrtaceae pollen (the dominant tree taxa in the region), while positive associations not attaining statistical significance were observed for Poaceae, Cyperaceae and Arecaceae. No associations were evident for any conditions with fungal spores. CONCLUSIONS: Our finding of an association between pollen count and respiratory hospital admissions that could not be explained by asthma admissions suggests that ambient airborne pollens might have a wider public health impact than previously recognized.     

Environmental risk factors and allergic bronchial asthma

The prevalence of allergic respiratory diseases such as bronchial asthma has increased in recent years, especially in industrialized countries. A change in the genetic predisposition is an unlikely cause of the increase in allergic diseases because genetic changes in a population require several generations. Consequently, this increase may be explained by changes in environmental factors, including indoor and outdoor air pollution. Over the past two decades, there has been increasing interest in studies of air pollution and its effects on human health. Although the role played by outdoor pollutants in allergic sensitization of the airways has yet to be clarified, a body of evidence suggests that urbanization, with its high levels of vehicle emissions, and a westernized lifestyle are linked to the rising frequency of respiratory allergic diseases observed in most industrialized countries, and there is considerable evidence that asthmatic persons are at increased risk of developing asthma exacerbations with exposure to ozone, nitrogen dioxide, sulphur dioxide and inhalable particulate matter. However, it is not easy to evaluate the impact of air pollution on the timing of asthma exacerbations and on the prevalence of asthma in general. As concentrations of airborne allergens and air pollutants are frequently increased contemporaneously, an enhanced IgE-mediated response to aeroallergens and enhanced airway inflammation could account for the increasing frequency of allergic respiratory allergy and bronchial asthma. Pollinosis is frequently used to study the interrelationship between air pollution and respiratory allergy. Climatic factors (temperature, wind speed, humidity, thunderstorms, etc) can affect both components (biological and chemical) of this interaction. By attaching to the surface of pollen grains and of plant-derived particles of paucimicronic size, pollutants could modify not only the morphology of these antigen-carrying agents but also their allergenic potential. In addition, by inducing airway inflammation, which increases airway permeability, pollutants overcome the mucosal barrier and could be able to "prime" allergen-induced responses. There are also observations that a thunderstorm occurring during pollen season can induce severe asthma attacks in pollinosis patients. After rupture by thunderstorm, pollen grains may release part of their cytoplasmic content, including inhalable, allergen-carrying paucimicronic particles.     

Non-linear short-term effects of airborne pollen levels with allergenic capacity on asthma emergency room admissions in Madrid, Spain

BACKGROUND: Several time-series studies have shown positive associations between pollen levels and asthma morbidity. However, few studies have included air pollution as a potential confounder when examining this relationship, and they have only done so on a linear basis. OBJECTIVE: To investigate the potential non-linear short-term effects of the types of pollen with allergenic capacity across the whole range of exposure on the daily number of asthma-related hospital emergencies in Madrid for the period 1995-1998. METHODS: Data were collected on the daily number of asthma emergency room admissions and daily average levels of major types of pollen with allergenic capacity: Olea, Plantago, Poaceae and Urticaceae. We used Poisson regression with generalized additive models, controlling for trend and seasonality, meteorological variables, acute respiratory infections and air pollutants. To study the non-linear effect of pollen levels on asthma emergency room admissions, pollens were categorized into five groups defined on the basis of their respective distributions. RESULTS: The strongest associations were registered in respect of a lag of 1 day for Urticaceae, a lag of 2 days for Plantago, and a day lag of 3 days for Poaceae. Adjustment for the different types of pollen failed to result in major changes. Non-linearities were evident for pollen levels. The greatest increase in risk vs. the reference category (minimum value - 50th percentile) was observed for the categories between the 95th and 99th percentiles, with increases of 32.0% for Plantago, 32.2% for Poaceae and 24.6% for Urticaceae, and between the 99th percentile and the maximum value, with increases of 31.3%, 78.7% and 49.8%, respectively. Olea was not related with asthma emergency room admissions. CONCLUSIONS: Pollens with allergenic capacity in Madrid are positively associated with asthma-related hospital emergencies. These associations remain stable when simultaneous adjustment is made for the four types of pollen and for air pollutants and meteorological variables. In terms of non-linear effects, Poaceae register the strongest association with asthma emergency room admissions.     

Omalizumab,a recombinant humanized anti-IgE antibody,reduces asthma-related emergency room visits and hospitalizations in patients with allergic asthma

BACKGROUND: Prevention of serious asthma exacerbations is an important therapeutic goal in patients with asthma. OBJECTIVE: The purpose of this study was to investigate the effect of omalizumab (Xolair), a recombinant humanized monoclonal anti-IgE antibody, on the rate of serious exacerbations during long-term therapy. METHODS: A pooled analysis was completed of 3 multicenter, randomized, double-blind, placebo-controlled phase III studies with omalizumab in adults/adolescents aged > or =12 years (n = 1071) and in children aged 6 to 12 years (n = 334) who required treatment with inhaled corticosteroids for allergic asthma. Rates of serious asthma exacerbations were computed and compared between omalizumab- and placebo-treated patients. Serious exacerbations were those leading to unscheduled outpatient visits, emergency room treatment, or hospitalization during 1 year of treatment. RESULTS: In all, 767 patients were treated with omalizumab (at least 0.016 mg/kg/IgE [IU/mL], administered subcutaneously every 4 weeks). Another 638 patients were treated with placebo. The rate of unscheduled, asthma-related outpatient visits was lower for the omalizumab-treated patients than for the placebo-treated patients (rate ratio [95% CI], 0.60 [0.44, 0.81]; P <.01), as were asthma-related emergency room visits (rate ratio [95% CI], 0.47 [0.24, 1.01]; P =.05). Importantly, hospitalizations for asthma were markedly reduced in patients receiving omalizumab (rate ratio [95% CI], 0.08 [0.00, 0.25]; P <.01). CONCLUSION: Omalizumab reduces the rate of serious asthma exacerbations and the need for unscheduled outpatient visits, emergency room treatment, and hospitalization in patients with moderate-to-severe allergic asthma.     

Air pollution and seasonal asthma during the pollen season. A cohort study in Puertollano and Ciudad Real (Spain)

BACKGROUND: Many studies have demonstrated a positive association between air pollutants and emergency visits for asthma. However, few studies have included pollen when analysing this relationship in mild-moderate asthmatic patients. OBJECTIVE: To determine the importance of the pollutants such as ozone (O(3)), particles (PM(10)), nitrogen dioxide (NO(2)) and sulphur dioxide (SO(2)) in the clinical course of mild-moderate pollen-allergic asthmatic patients from two Spanish towns in La Mancha: Puertollano (high pollution levels) and Ciudad Real (low pollution levels). METHODS: We used a Poisson regression model to study a cohort of 137 patients from Puertollano and Ciudad Real during two pollen seasons (2000-2001) and analysed the relationship between air pollutant and pollen levels and daily symptoms, the medication used and peak-flow measurements. RESULTS: The number of asthma symptoms and the mean values of the PM(10), SO(2) and NO(2) levels were higher in Puertollano than in Ciudad Real. In Puertollano, the risk of asthma increased by 6% with a 3-day lag for PM(10), by 8% with a 3-day lag for O(3), by 4% with a 1-day lag for SO(2) and by 15% with a 3-day lag for O(3) when its values exceeded the health threshold (P < 0.05). CONCLUSIONS: The air pollution levels in Puertollano were associated with an increased risk of asthma symptoms in pollen-allergic asthmatic patients com pared with a similar group from Ciudad Real.     

Asthma control and future asthma-related morbidity in inner-city asthmatic children

BACKGROUND: Asthma guidelines recommend routine evaluation of asthma control, which includes measurements of impairment and risk. It is unclear whether rigorous asthma control changes risk of asthma morbidity. OBJECTIVE: To examine whether the degree of asthma control in inner-city asthmatic children results in differential risk reduction of future asthma-related morbidity. METHODS: This retrospective observational study examines 960 inner-city children with asthma who were highly engaged in an asthma-specific disease management program for a minimum of 2 years. Degree of asthma control was determined during the first year of enrollment and was categorized as well controlled (> or = 80% of visits in control), moderately controlled (50%-79% of visits in control), or difficult to control (< 50% of visits in control). Risk and probability of asthma-related morbidity at each visit were determined during the second year of enrollment and included self-reported asthma exacerbations requiring systemic corticosteroid rescue and emergency department visits or hospitalizations. RESULTS: Increasing the degree of asthma control measured during the first year of enrollment led to statistically significant incremental reductions in risk of acute asthma exacerbations and emergency department visits or hospitalizations during the second year of enrollment. CONCLUSIONS: Achieving and maintaining asthma control in inner-city children with asthma results in significant reductions in asthma-related morbidity. Systematic assessments of asthma control may be useful for predicting future risk in children with asthma.     

Airborne fungi in the homes of children with asthma in low-income urban communities: The Inner-City Asthma Study

BACKGROUND: Despite growing evidence of the importance of exposure to fungi as an environmental risk factor for asthma, few data have been reported on the exposure to airborne fungi of asthmatic children living in US inner cities. OBJECTIVE: We sought to examine the spectrum and concentration of fungi in the air inside and outside of the homes of mold-sensitive children with asthma living in US cities. We also analyzed the relationship of the concentration of fungi in indoor air to home characteristics. METHODS: We performed a home environmental survey and measured the concentrations of culturable airborne fungi inside and outside the homes of 414 mold-sensitive children with asthma in 7 urban communities. RESULTS: The airborne fungi encountered indoors generally paralleled those found outdoors, and the similarities between communities were more striking than the differences. Indoor fungal concentrations were correlated with outdoor concentrations measured on the same day, suggesting the need to adjust for the outdoor concentration in analyses by using the indoor concentration as an indicator of the relative moldiness of a home. The concentration of fungi in indoor air in excess of outdoor air-that is, the indoor-outdoor difference-was significantly related to home characteristics, including dampness, having a cat, and cockroach infestation. CONCLUSION: Mold-sensitive children with asthma living in urban communities across the US are exposed to airborne fungi in indoor and outdoor air. The concentrations of fungi are higher in homes with dampness problems, cockroach infestation, and cats. The indoor-outdoor difference in the concentration of airborne fungi may provide a valuable metric for investigations of the role of fungal exposure as a risk factor for asthma.     

Comparison of outdoor allergenic particles and allergen levels.

INTRODUCTION: Spore and pollen counts have been used traditionally to determine aeroallergen exposure. Using a liquid based collector and enzyme immunoassays, we have developed methods for measuring airborne allergen concentrations. In this work we test the hypothesis that airborne allergen concentrations are directly related to spore and pollen counts. METHODS: Test samplers used included a high-volume cyclonic liquid impinger (SpinCon) and a standard spore trap (Burkard). Samples were collected on a weekly basis from May to October and were analyzed microscopically for spores and pollen grains. The liquid samples were analyzed by enzyme-linked immunoassay for the presence of allergens from Alternaria, Cladosporium, Aspergillus, oak, fescue, ragweed, and plantain. Specific Alternaria allergens Alt al and GP70 also were measured. RESULTS: Pollen counts for the SpinCon and Burkard collectors were similar, though spore counts were lower with the SpinCon. Detectable amounts of three of the seven allergenic species including fescue, ragweed, and Alternaria were present in air samples. Concentrations of pollens were seen in their respective seasons while fungal allergen levels varied throughout the period. Allergen levels generally agreed with particle counts, however peak allergen levels and peak particle counts for individual species did not correlate well. CONCLUSIONS: At flow rates of 236 L/min, the SpinCon is comparable to the Burkard for counting airborne pollen and spores. Samples collected by the SpinCon permit quantitative determination of allergen levels in outdoor air. The poor correlation between measured airborne allergen and related particles indicates the potential for significant allergen exposure in the absence of identifiable particles in air.     

Outdoor pollen is a trigger of child and adolescent asthma emergency department presentations: A systematic review and meta‐analysis

Background

In the context of increased asthma exacerbations associated with climatic changes such as thunderstorm asthma, interest in establishing the link between pollen exposure and asthma hospital admissions has intensified. Here, we systematically reviewed and performed a meta‐analysis of studies on pollen and emergency department (ED) attendance.

Methods

A search for studies with appropriate search strategy in MEDLINE, EMBASE, Web of Science and CINAHL was conducted. Each study was assessed for quality and risk of bias. The available evidence was summarized both qualitatively and meta‐analysed using random‐effects models when moderate heterogeneity was observed.

Results

Fourteen studies were included. The pollen taxa investigated differed between studies, allowing meta‐analysis only of the effect of grass pollen. A statistically significant increase in the percentage change in the mean number of asthma ED presentations (MPC) (pooled results from 3 studies) was observed for an increase in 10 grass pollen grains per cubic metre of exposure 1.88% (95% CI = 0.94%, 2.82%). Time series studies showed positive correlations between pollen concentrations and ED presentations. Age‐stratified studies found strongest associations in children aged 5‐17 years old.

Conclusion

Exposure to ambient grass pollen is an important trigger for childhood asthma exacerbations requiring ED attendance. As pollen exposure is increasingly a problem especially in relation to thunderstorm asthma, studies with uniform measures of pollen and similar analytical methods are necessary to fully understand its impact on human health.     

Do levels of airborne grass pollen influence asthma hospital admissions?

Background The effects of environmental factors and ambient concentrations of grass pollen on allergic asthma are yet to be established.
Objective We sought to estimate the independent effects of grass pollen concentrations in the air over Melbourne on asthma hospital admissions for the 1992–1993 pollen season.
Methods Daily grass pollen concentrations were monitored over a 24-h period at three stations in Melbourne. The outcome variable was defined as all-age asthma hospital admissions with ICD9-493 codes. The ambient air pollutants were average daily measures of ozone, nitrogen dioxide and sulphur dioxide, and the airborne particle index representing fine particulate pollution. Semi-parametric Poisson regression models were used to estimate these effects, adjusted for air temperature, humidity, wind speed, rainfall, day-of-the-week effects and seasonal variation.
Results Grass pollen was a strong independent non-linear predictor of asthma hospital admissions in a multi-pollutant model ( P =0.01). Our data suggest that grass pollen had an increasing effect on asthma hospital admissions up to a threshold of 30 grains/m³, and that the effect remains stable thereafter.
Conclusion Our findings suggest that grass pollen levels influence asthma hospital admissions. High grass pollen days, currently defined as more than 50 grains/m³, are days when most sensitive individuals will experience allergic symptoms. However, some asthmatic patients may be at a significant risk even when airborne grass pollen levels are below this level. Patients with pollen allergies and asthma would be advised to take additional preventive medication at lower ambient concentrations.     

Allergy in severe asthma

It is well recognized that atopic sensitization is an important risk factor for asthma, both in adults and in children. However, the role of allergy in severe asthma is still under debate. The term ‘Severe Asthma’ encompasses a highly heterogeneous group of patients who require treatment on steps 4–5 of GINA guidelines to prevent their asthma from becoming ‘uncontrolled’, or whose disease remains ‘uncontrolled’ despite this therapy. Epidemiological studies on emergency room visits and hospital admissions for asthma suggest the important role of allergy in asthma exacerbations. In addition, allergic asthma in childhood is often associated with severe asthma in adulthood. A strong association exists between asthma exacerbations and respiratory viral infections, and interaction between viruses and allergy further increases the risk of asthma exacerbations. Furthermore, fungal allergy has been shown to play an important role in severe asthma. Other contributing factors include smoking, pollution and work‐related exposures. The ‘Allergy and Asthma Severity’ EAACI Task Force examined the current evidence and produced this position document on the role of allergy in severe asthma.     

Effects of air pollution on asthma hospitalization rates in different age groups in Hong Kong

AIMS: To assess the relationship between levels of ambient air pollutants and hospitalization rates for asthma in Hong Kong (HK). METHODS: This is a retrospective ecological study. Data of daily emergency hospital admissions to 15 major hospitals in HK for asthma and indices of air pollutants [sulphur dioxide (SO(2)), nitrogen dioxide (NO(2)), ozone (O(3)), particulates with an aerodynamic diameter of <10 microm particulate matter (PM(10)) and 2.5 microm (PM(2.5))] and meteorological variables from January 2000 to December 2005 were obtained from several government departments. Analysis was performed by the generalized additive models with Poisson distribution. The effects of time trend, season, other cyclical factors, temperature and humidity were adjusted. Autocorrelation and overdispersion were corrected. RESULTS: Altogether, 69 716 admissions were assessed. Significant associations were found between hospital admissions for asthma and levels of NO(2), O(3), PM(10) and PM(2.5). The relative risks (RR) for hospitalization for every 10 microg/m(3) increase in NO(2), O(3), PM(10) and PM(2.5) were 1.028, 1.034, 1.019 and 1.021, respectively, at a lag day that ranged from cumulative lag 0-4 to 0-5. In a multi-pollutant model, O(3) was significantly associated with increased admissions for asthma. The younger age group (0-14 years) tended to have a higher RR for each 10 microg/m(3) increase in pollutants than those aged 15-65 years. The elderly (aged >/=65 years) had a shorter 'best' lag time to develop asthma exacerbation following exposure to pollutants than those aged <65 years. CONCLUSION: Adverse effects of ambient concentrations of air pollutants on hospitalization rates for asthma are evident. Measures to improve air quality in HK are urgently needed.     

Benefits of omalizumab as add-on therapy in patients with severe persistent asthma who are inadequately controlled despite best available therapy (GINA 2002 step 4 treatment): INNOVATE

BACKGROUND: Patients with severe persistent asthma who are inadequately controlled despite Global Initiative for Asthma (GINA) 2002 step 4 therapy are a challenging population with significant unmet medical need. We determined the effect of omalizumab on clinically significant asthma exacerbations (requiring systemic corticosteroids) in the first omalizumab study to exclusively enrol patients from this difficult-to-treat patient population. METHODS: Following a run-in phase, patients (12-75 years) inadequately controlled despite therapy with high-dose inhaled corticosteroids (ICS) and long-acting beta(2)-agonists (LABA) with reduced lung function and a recent history of clinically significant exacerbations were randomized to receive omalizumab or placebo for 28 weeks in a double-blind, parallel-group, multicentre study. RESULTS: A total of 419 patients were included in the efficacy analyses. The clinically significant asthma exacerbation rate (primary efficacy variable), adjusted for an observed relevant imbalance in history of clinically significant asthma exacerbations, was 0.68 with omalizumab and 0.91 with placebo (26% reduction) during the 28-week treatment phase (P = 0.042). Without adjustment, a similar magnitude of effect was seen (19% reduction), but this did not reach statistical significance. Omalizumab significantly reduced severe asthma exacerbation rate (0.24 vs 0.48, P = 0.002) and emergency visit rate (0.24 vs 0.43, P = 0.038). Omalizumab significantly improved asthma-related quality of life, morning peak expiratory flow and asthma symptom scores. The incidence of adverse events was similar between treatment groups. CONCLUSIONS: In patients with inadequately controlled severe persistent asthma, despite high-dose ICS and LABA therapy, and often additional therapy, omalizumab significantly reduced the rate of clinically significant asthma exacerbations, severe exacerbations and emergency visits. Omalizumab is effective and should be considered as add-on therapy for patients with inadequately controlled severe persistent asthma who have a significant unmet need despite best available therapy.     

支气管热成形术治疗难治性哮喘研究进展

难治性哮喘是指大剂量吸入激素（ICS）或口服ICS仍难以控制的一类哮喘,因其长期反复发作,严重影响患者的生活质量,并导致大量的医疗资源消耗。支气管热成形术（BT）作为针对难治性哮喘的一种新型治疗方法,主要通过射频消融减少气道平滑肌数量而发挥作用。如今,越来越多的数据表明BT可有效控制难治性哮喘患者的哮喘症状、降低急性发作率、提高患者生活质量。本文主要对BT的临床应用、影像学在BT中的使用以及BT对气道病理学的影响等进行综述,为临床医生更好选择BT治疗患者、评估患者病情提供帮助。     

The seasonal variation in allergic rhinitis and its correlation with outdoor allergens in Kuwait

BACKGROUND: Allergic rhinitis (AR) is the most common allergic problem in Kuwait. Most of the patients who have either AR or asthma are referred to the Al-Rashed Allergy Center. OBJECTIVE: To determine if there is a seasonal variation in AR in Kuwait and to correlate it with the daily pollen count. METHODS: Information about the new patients referred to the center over a 5-year study period (1996-2000) was extracted from the center's records. The daily pollen count in Kuwait city was obtained from the Air Biology Laboratory. RESULTS: There was a significant seasonal variation with a bimodal increase in the number of patients with AR referred to the center. The main peak in the number of patients occurred in September-October, and there was a smaller peak in April-May. The mean number +/- SD of new patients per month over the 5-year period varied from 87 +/- 32 for December to 367 +/- 104 for September. Similarly, the average daily pollen count varied from 3.7 +/- 1.0 pollens per mm3 in January to 124 +/- 92 in October. There was high correlation between the number of new AR patients and the average total pollen count (Pearson correlation, r=0.77, p<0.001), as well as with Chenopodiaceae and Amaranthaceae (weed) pollens (r=0.75, p<0.001), while there was no correlation between the number of new patients and either tree or grass pollens. CONCLUSION: Seasonal AR occurs during two periods in Kuwait, i.e. September-October and April-May, with September-October being the main season. The rise in AR during late summer in Kuwait is mainly associated with the pollination of Chenopodiaceae species.     

Effects of wintertime ambient air pollutants on asthma exacerbations in urban minority children with moderate to severe disease

BACKGROUND: Urban minority children with asthma are at higher risk for severe exacerbations leading to hospitalizations and deaths. Because multiple studies have reported associations between air pollution and asthma worsening, elevated levels of air pollution are cited as a possible trigger for increased asthma morbidity in urban areas. Few studies have prospectively followed panels of urban children with asthma to determine whether air pollution levels are associated with clinically relevant outcomes such as asthma exacerbations. OBJECTIVE: To determine the association between levels of ambient air pollutants and asthma exacerbations in urban poor children with moderate to severe asthma. METHODS: A school-based panel of children with difficult-to-control disease was followed over a period of 3 consecutive winters in Denver, Colo. The panel consisted of predominantly urban African American children with moderate to severe asthma. Levels of Environmental Protection Agency criteria air pollutants were measured on a daily basis with concurrent monitoring of lung function, bronchodilator use, symptoms, and asthma exacerbations. RESULTS: After controlling for time-varying factors such as upper respiratory infections and meteorologic factors, a weak association was found between ambient carbon monoxide levels and bronchodilator use. Ozone levels were associated with daytime symptoms only. No association was observed between daily air pollution concentrations and daily levels of FEV 1 , peak flow, nighttime symptom scores, or asthma exacerbations over the 3-year period. CONCLUSION: Ambient levels of Environmental Protection Agency criteria air pollutants in Denver do not lead to clinically significant asthma worsening in urban children with moderate to severe asthma during winter months when children are primarily indoors.