Background. The risk of developing childhood asthma
has been linked to the severity and etiology of viral respiratory illnesses in early
childhood. Since inner-city infants have unique environmental exposures, we hypothesized
that patterns of respiratory viral infections would also be distinct.
Methods. We compared the viral etiology of respiratory
illnesses in 2 groups: a cohort of 515 infants from 4 inner-city areas and a cohort of 285
infants from mainly suburban Madison, Wisconsin. Nasal secretions were sampled during
periods of respiratory illness and at 1 year of age and were analyzed for viral pathogens
by multiplex polymerase chain reaction.
Results. Overall, inner-city infants had lower rates
of viral detection. Considering specific viruses, sick urban infants had lower rates of
detectable rhinovirus or respiratory syncytial virus infection and higher rates of
adenovirus infection. Every urban site had a higher proportion of adenovirus-positive
samples associated with illnesses (10%–21%), compared with Madison
Conclusions. These findings provide evidence that
inner-city babies have different patterns of viral respiratory illnesses than babies who
grow up in a more suburban location. These findings raise important questions about the
etiology of virus-negative illnesses in urban infants and the possibility of long-term
consequences of early life infections with adenovirus in this population.
Rationale: Human rhinoviruses (HRVs) consist of approximately 160 types that cause a wide range of clinical outcomes, including asymptomatic infections, common colds, and severe lower respiratory illnesses.
Objectives: To identify factors that influence the severity of HRV illnesses.
Methods: HRV species and types were determined in 1,445 nasal lavages that were prospectively collected from 209 infants participating in a birth cohort who had at least one HRV infection. Questionnaires were used during each illness to identify moderate to severe illnesses (MSI).
Measurements and Main Results: Altogether, 670 HRV infections were identified, and 519 of them were solitary infections (only one HRV type). These 519 viruses belonged to 93 different types of three species: 49 A, 9 B, and 35 C types. HRV-A (odds ratio, 8.2) and HRV-C (odds ratio, 7.6) were more likely to cause MSI compared with HRV-B. In addition, HRV infections were 5- to 10-fold more likely to cause MSI in the winter months (P < 0.0001) compared with summer, in contrast to peak seasonal prevalence in spring and fall. When significant differences in host susceptibility to MSI (P = 0.004) were considered, strain-specific rates of HRV MSI ranged from less than 1% to more than 20%.
Conclusions: Factors related to HRV species and type, season, and host susceptibility determine the risk of more severe HRV illness in infancy. These findings suggest that anti-HRV strategies should focus on HRV-A and -C species and identify the need for additional studies to determine mechanisms for seasonal increases of HRV severity, independent of viral prevalence, in cold weather months.
rhinovirus; severe illness; species; type; seasonality
Both genetic variation at the 17q21 locus and virus-induced respiratory wheezing illnesses are associated with the development of asthma. Our aim was to determine the effects of these two factors on the risk of asthma in the Childhood Origins of Asthma (COAST) and the Copenhagen Prospective Study on Asthma in Childhood (COPSAC) birth cohorts.
We tested genotypes at the 17q21 locus for associations with asthma and with human rhinovirus (HRV) and respiratory syncytial virus (RSV) wheezing illnesses and tested for interactions between 17q21 genotypes and HRV and RSV wheezing illnesses with respect to the risk of asthma. Finally, we examined genotype-specific expression of 17q21 genes in unstimulated and HRV-stimulated peripheral-blood mononuclear cells (PBMCs).
The 17q21 variants were associated with HRV wheezing illnesses in early life, but not with RSV wheezing illnesses. The associations of 17q21 variants with asthma were restricted to children who had had HRV wheezing illnesses, resulting in a significant interaction effect with respect to the risk of asthma. Moreover, the expression levels of ORMDL3 and of GSDMB were significantly increased in HRV-stimulated PBMCs, as compared with unstimulated PBMCs. The expression of these genes was associated with 17q21 variants in both conditions, although the increase with exposure to HRV was not genotype-specific.
Variants at the 17q21 locus were associated with asthma in children who had had HRV wheezing illnesses and with expression of two genes at this locus. The expression levels of both genes increased in response to HRV stimulation, although the relative increase was not associated with the 17q21 genotypes. (Funded by the National Institutes of Health.)
Children with allergic asthma have more frequent and severe human rhinovirus (HRV)-induced wheezing and asthma exacerbations through unclear mechanisms.
To determine whether increased high-affinity IgE receptor (FcεRI) expression and cross-linking impairs innate immune responses to HRV, particularly in allergic asthmatic children.
Peripheral blood mononuclear cells (PBMC) were obtained from 44 children and surface expression of FcεRI on plasmacytoid dendritic cells (pDCs), myeloid dendritic cells (mDCs), monocytes, and basophils was assessed using flow cytometry. Cells were also incubated with rabbit anti-human IgE to cross-link FcεRI, followed by stimulation with HRV-16, and interferon (IFN)-α and -λ1 were measured by Luminex. The relationships among FcεRI expression and cross-linking, HRV-induced IFN-α and -λ1 production, and childhood allergy and asthma were subsequently analyzed.
FcεRIα expression on pDCs was inversely associated with HRV-induced IFN- α and IFN-λ1 production. Cross-linking FcεRI prior to HRV stimulation further reduced PBMC IFN-α (47% relative reduction, 95% confidence interval [CI], 32–62%, p<0.0001) and IFN-λ1 (81% relative reduction, 95% CI, 69–93%, p<0.0001) secretion. Allergic asthmatic children had higher surface expression of FcεRIα on pDCs and mDCs when compared to non-allergic non-asthmatic children. Further, after FcεRI cross-linking, allergic asthmatic children had significantly lower HRV-induced IFN responses than allergic non-asthmatics (IFN-α, p=0.004; IFN-λ1, p=0.02) and non-allergic non-asthmatics (IFN-α, p=0.002; IFN-λ1, p=0.01).
Allergic asthmatic children have impaired innate immune responses to HRV that correlate with increased FcεRI expression on pDCs and are reduced by FcεRI cross-linking. These effects likely increase susceptibility to HRV-induced wheezing and asthma exacerbations.
asthma; allergic; rhinovirus; interferon; FcεRI; IgE receptor; plasmacytoid dendritic cells
Viral illnesses are important factors in both asthma inception and exacerbations, and allergic sensitization in early life further enhances asthma risk through unclear mechanisms. Cellular damage due to infection or allergen inhalation increases ATP in the airways with subsequent purinergic receptor activation. The purinergic receptor P2X7 may enhance airway leukocyte recruitment to the airways and P2X7 knockout mice display a reduced asthma-like phenotype.
Based upon the P2X7 knockout mouse, we hypothesized that children with low functioning P2X7 would have decreased rates of asthma.
We utilized a functional assay to determine P2X7 pore-producing capacity in whole blood samples in a birth cohort study at high risk for asthma development. The P2X7 assay was validated with known loss-of-function alleles in humans. P2X7 pore status categorization was used to assess asthma and allergy status in the cohort.
Attenuated P2X7 function was associated with lower asthma rates at ages 6 and 8 and the greatest effects were observed in boys. Children with asthma at age 11 who had low P2X7 capacity had less severe disease in the previous year. Attenuated P2X7 function was also associated with sensitization to fewer aeroallergens.
P2X7 functional capacity is associated with asthma risk or disease severity and these relationships appear to be age-related.
asthma; allergy; children; P2X7; ATP
The National Heart, Lung and Blood Institute (NHLBI) Asthma Clinical Research Network (ACRN) recently completed its work after 20 years of collaboration as a multicentre clinical trial network. When formed, its stated mission was to perform multiple controlled clinical trials for treating patients with asthma by dispassionately examining new and existing therapies, and to rapidly communicate its findings to the medical community. The ACRN conducted 15 major clinical trials. In addition, clinical data, manual of operations, protocols and template informed consents from all ACRN trials are available via NHLBI BioLINCC (https://biolincc.nhlbi.nih.gov/studies/). This network contributed major insights into the use of inhaled corticosteroids, short-acting and long-acting ß-adrenergic agonists, leukotriene receptor antagonists, and novel agents (tiotropium, colchicine and macrolide antibiotics). They also pioneered studies of the variability in drug response, predictors of treatment response and pharmacogenetics. This review highlights the major research observations from the ACRN that have impacted the current management of asthma.
Rationale: The 2009 H1N1 flu appeared to cause more severe cold symptoms during the 2009–2010 flu season.
Objectives: We evaluated H1N1 infections during peak viral season in children with and without asthma to determine whether the H1N1 infectivity rate and illness severity were greater in subjects with asthma.
Methods: One hundred and eighty children, 4–12 years of age, provided eight consecutive weekly nasal mucus samples from September 5 through October 24, 2009, and scored cold and asthma symptoms daily. Viral diagnostics were performed for all nasal samples.
Measurements and Main Results: One hundred and sixty-one children (95 with asthma, 66 without asthma) completed at least 6 of the 8 nasal samples. The incidence of H1N1 infection was significantly higher in children with asthma (41%) than in children without asthma (24%; odds ratio, 4; 95% confidence interval, 1.8–9; P < 0.001), but rates of human rhinovirus infection (90% each) and other viral infections (47 vs. 41%) were similar. In children with asthma, there was a nonsignificant trend for increased loss of asthma control during H1N1 infections compared with human rhinovirus infections (38 vs. 21%; odds ratio, 2.6; 95% confidence interval, 0.9–7.2; P = 0.07).
Conclusions: During peak 2009 H1N1 flu season, children with asthma were infected almost twice as often with H1N1 compared with other respiratory viruses. H1N1 infection also caused increased severity of cold symptoms compared with other viral infections. Given the increased susceptibility of children with asthma to infection, these findings reinforce the need for yearly influenza vaccination to prevent infection, and raise new questions about the mechanism for enhanced susceptibility to influenza infection in asthma.
asthma; viral infection; influenza
Severe wheezing exacerbations during the preschool years, a critical time in lung growth and development, may lead to airway damage and remodeling. Our study linked these events to a partially reversible reduction in lung function present at school age.
exacerbation; lung function; childhood; wheezing; corticosteroids
Rationale: Aeroallergen sensitization and virus-induced wheezing are risk factors for asthma development during early childhood, but the temporal developmental sequence between them is incompletely understood.
Objective: To define the developmental relationship between aeroallergen sensitization and virus-induced wheezing.
Methods: A total of 285 children at high risk for allergic disease and asthma were followed prospectively from birth. The timing and etiology of viral respiratory wheezing illnesses were determined, and aeroallergen sensitization was assessed annually for the first 6 years of life. The relationships between these events were assessed using a longitudinal multistate Markov model.
Measurements and Main Results: Children who were sensitized to aeroallergens had greater risk of developing viral wheeze than nonsensitized children (hazard ratio [HR], 1.9; 95% confidence interval [CI], 1.2–3.1). Allergic sensitization led to an increased risk of wheezing illnesses caused by human rhinovirus (HRV) but not respiratory syncytial virus. The absolute risk of sensitized children developing viral wheeze was greatest at 1 year of age; however, the relative risk was consistently increased at every age assessed. In contrast, viral wheeze did not lead to increased risk of subsequent allergic sensitization (HR, 0.76; 95% CI, 0.50–1.1).
Conclusions: Prospective, repeated characterization of a birth cohort demonstrated that allergic sensitization precedes HRV wheezing and that the converse is not true. This sequential relationship and the plausible mechanisms by which allergic sensitization can lead to more severe HRV-induced lower respiratory illnesses support a causal role for allergic sensitization in this developmental pathway. Therefore, therapeutics aimed at preventing allergic sensitization may modify virus-induced wheezing and the development of asthma.
virus; wheezing; allergic sensitization; RSV; human rhinovirus
Asthma is a complex disease characterized by sex-specific differences in incidence, prevalence and severity, but little is known about the molecular basis of these sex differences. Objective: To investigate the genetic architecture of sex differences in asthma risk, we evaluated i) associations between polymorphisms in the interferon-gamma (IFNG) gene and childhood onset asthma in combined and sex-specific samples, and ii) interactions between polymorphisms and sex on asthma risk.
Main and sex-interaction effects of IFNG genetic diversity on asthma risk and IFN-γ levels were examined in a birth cohort of children at high risk for asthma and allergic diseases. Replication of the genetic association was assessed in an independent sample of asthma cases.
Significant genotype-by-sex interactions on asthma were observed for two IFNG SNPs, rs2069727 and rs2430561, which were in strong linkage disequilibrium with each other. In contrast, none of the ten IFNG SNPs showed significant main effects on asthma. The observed genotype-by-sex interaction on asthma was characterized by non-additivity, i.e. heterozygote boys had the highest risk for asthma, while heterozygote girls had the lowest risk. The interaction effect was robust to other asthma risk factors but was limited to children who experienced wheezing illnesses with viral infections during the first three years of life. Genotype-by-sex interactions were also observed in IFN-γ response to LPS in the first year of life. Finally, the sex interaction effect was replicated in an independent population of childhood asthma cases.
These results provide insight into the genetic basis of sex differences in asthma and highlight the potential importance of interactions among sex, genotype, and environmental factors in asthma pathogenesis.
IFN-γ; asthma; children; sex differences; single nucleotide polymorphism; association study
Asthma is a heterogenous disorder that is characterized by variable airflow obstruction, airway inflammation and hyperresponsiveness, and reversibility either spontaneously or as a result of treatment. Multiple etiologies no doubt exist for both its inception and symptom exacerbation once the disease is established. Factors underlying inception can range from viral respiratory tract infections in infancy(1,2) to occupational exposures in adults.(3) Factors underlying asthma exacerbations include allergen exposure in sensitized individuals, viral infections, exercise, irritants, ingestion of nonsteroidal anti-inflammatory agents, among others. Exacerbating factors may include one or all of these exposures, and vary both among and within patients. Asthma treatment is determined to a large extent following an initial assessment of severity and subsequent establishment of control, both of which can be variable over time and assessed in two domains: impairment (current) and risk (long term consequences).(4) Unfortunately, despite the availability of effective therapies, suboptimal asthma control exists in many patients on a world-wide basis.(5) The future development of novel therapies and treatment paradigms should address these disparities.
Asthma; Respiratory syncytial virus; Rhinovirus; Allergen; Prevention; Exacerbation; Inception; Treatment
The variability in symptom control is a challenging feature of asthma that necessitates careful monitoring and the need to step-up and step-down individualized therapeutic regimens over time. This stepwise concept in asthma therapy can be considered in at least three contexts. For lack of control that is persistent over long periods of time, an increase in the overall medication or a “step-up long-term (SLT)” is indicated. A second approach, “step-up short-term (SST)”, may be utilized during a temporary loss of acceptable control, such as at the onset of a viral respiratory tract illness. In these cases, a step-up in therapy is usually terminated in 3–10 days once asthma control has been satisfactorily achieved. Finally, for treating symptoms related to the variability of asthma on a day to day basis, ICS used concomitantly with a beta agonist has been evaluated, though not currently approved in the United States. We will term this particular intervention as “step-up intermittent (SUI).” Here we summarize the existing data regarding these three approaches to step-up care, step-down management, as well as identify areas where more comparative studies are necessary to provide further guidance to clinicians regarding proper step-up and step-down strategies in the care of asthma.
asthma; step-up; step-down; stepwise; guidelines; severity; control; step-up intermittent; step-up short-term; step-up long-term
The effect on linear growth of daily long-term inhaled corticosteroid (ICS) therapy in preschool-aged children with recurrent wheezing is controversial.
To determine the effect of daily ICS given for 2 years on linear growth in preschool children with recurrent wheezing.
Children ages 2 and 3 years with recurrent wheezing and positive modified asthma predictive indices were randomized to a two-year treatment period of fluticasone propionate CFC (176 mcg/day) or masked-placebo delivered by valved chamber with mask and then followed 2 years off study medication. Height growth determined by stadiometry was compared between treatment groups.
In the study cohort as a whole, the fluticasone group did not have significantly less linear growth than the placebo-group [change in height from baseline difference (ΔHt) of −0.2 cm (95% CI, −1.1, 0.6)] two years after discontinuation of study treatment. In post-hoc analyses, children 2 years old and who weighed < 15 kg at enrollment treated with fluticasone had less linear growth compared to placebo [ΔHt of −1.6 cm (95% CI, −2.8, −0.4), p=0.009].
Linear growth was not significantly different in high-risk, recurrent wheezing preschool age children treated with CFC fluticasone 176 mcg/day compared to placebo 2 years after fluticasone is discontinued. However, post-hoc subgroup analyses revealed that children who are younger in age and of lesser weight relative to the entire study cohort had significantly less linear growth, possibly due to a higher relative fluticasone exposure.
Asthma predictive index; atopy; clinical trials; early childhood asthma; fluticasone; inhaled corticosteroids; intermittent wheezing; linear growth; research network
Although nocturnal awakenings help categorize asthma severity and control, their clinical significance has not been thoroughly studied.
To determine the clinical consequences of nocturnal asthma symptom(s) requiring albuterol in children with mild-to-moderate persistent asthma outside of periods when oral corticosteroids were used for worsening asthma symptoms.
285 children ages 6 to 14 years with mild-to-moderate persistent asthma were randomized to receive one of three controller regimens and completed daily symptom diaries for 48 weeks. Diary responses were analyzed for the frequency and consequences of nocturnal asthma symptoms requiring albuterol.
Nocturnal asthma symptoms requiring albuterol occurred in 72.2% of participants at least once and in 24.3% ≥13 times. 81.3% of nocturnal symptoms occurred outside of exacerbation periods and were associated the next day with the following events: albuterol use (56.9% of days preceded by nocturnal symptoms versus 18.1% of days not preceded by nocturnal symptoms, Relative Risk (RR) 2.3, 95%CI: 2.2,2.4), school absence (5.0% versus 0.3%, RR 10.6, 95%CI: 7.8,14.4), and doctor contact (3.7% versus 0.2%, RR 8.8, 95%CI:6.1,12.5). Similar findings were noted during exacerbation periods (RR 1.7 for albuterol use, 5.5 for school absence, and 4.9 for doctor contact). Nocturnal symptoms did not predict the onset of exacerbations.
Nocturnal symptoms requiring albuterol in children with mild-to-moderate persistent asthma receiving controller therapy occurred predominantly outside of exacerbation periods. Despite being poor predictors of exacerbations, they were associated with increases in albuterol use, school absences, and doctor contacts the day after nocturnal symptom occurrences.
asthma; nocturnal symptoms; exacerbation
Asthma is a heterogenous disorder related to numerous biologic, immunologic, and physiologic components that generate multiple clinical phenotypes. Further, genetic and environmental factors interact in ways that produce variability in both disease onset and severity and differential expression based on both the age and sex of the patient. Thus, the natural history of asthma is complex in terms of disease expression, remission, relapse, and progression. As such, therapy for asthma is complicated and has been approached from the standpoints of primary, secondary, and tertiary prevention. Presently, asthma cannot be cured but can be controlled in most patients, an indication that most of the success clinical research strategies have realized has been in the area of tertiary prevention. Since for many adult patients with asthma their disease had its roots in early life, much recent research has focused on events during early childhood that can be linked to subsequent asthma development with the hopes of creating appropriate interventions to alter its natural history of expression. These research approaches can be categorized into three questions. Who is the right patient to treat? When is the right time to begin treatment? And finally, what is the appropriate treatment to prescribe?
asthma; therapy; inhaled corticosteroids; β-agonists
Preschool rhinovirus wheezing illnesses predict an increased risk of childhood asthma; however, it is not clear how specific viral illnesses in early life relate to lung function later on in childhood.
To determine the relationshipof virus-specific wheezing illnesses and lung function in a longitudinal cohort of children at risk for asthma.
Two hundred thirty-eight children were followed prospectivelyfrom birth to 8 years of age. Early life viral wheezing respiratory illnesses were assessed using standard techniques and lung function was assessed annually by spirometry and impulse oscillometry (IOS). The relationshipsof these virus-specific wheezing illnesses and lung function were assessed by mixed-effect linear regression.
Children who wheezed with rhinovirus (RV) demonstrated significantly decreased spirometry values [FEV1 (p=0.001), FEV0.5 (p<0.001), FEF25–75 (p<0.001)], and also had abnormal IOS measures [more negative Reactance at 5 Hz (p<0.001)] compared to those who did not wheeze with RV. Children who wheezed with RSV or other viral illnesses did not have any significant differences in spirometric or IOS indices when compared to children who did not. Children diagnosed with asthma at ages 6 or 8 years had significantly decreased FEF25–75 (p=0.05) compared to children without asthma.
Among outpatient viral wheezing illnesses in early childhood, those caused by RV infections are the mostsignificant predictors of decreased lung functionup to age 8 years in a high-risk birth cohort. Whether low lung function is a cause and/or effect of RV wheezing illnesses has yet to be determined.
rhinovirus; respiratory syncytial virus; wheezing; asthma; spirometry; impulse oscillometry
Genome-wide association studies of asthma have implicated many genetic risk factors, with
well-replicated associations at approximately 10 loci that account for only a small proportion of
the genetic risk.
We aimed to identify additional asthma risk loci by performing an extensive replication
study of the results from the EVE Consortium meta-analysis.
We selected 3186 SNPs for replication based on the p-values from the EVE Consortium
meta-analysis. These SNPs were genotyped in ethnically diverse replication samples from nine
different studies, totaling to 7202 cases, 6426 controls, and 507 case-parent trios. Association
analyses were conducted within each participating study and the resulting test statistics were
combined in a meta-analysis.
Two novel associations were replicated in European Americans: rs1061477 in the
KLK3 gene on chromosome 19 (combined OR = 1.18; 95% CI 1.10 – 1.25)
and rs9570077 (combined OR =1.20 95% CI 1.12–1.29) on chromosome 13q21. We could not
replicate any additional associations in the African American or Latino individuals.
This extended replication study identified two additional asthma risk loci in populations
of European descent. The absence of additional loci for African Americans and Latino individuals
highlights the difficulty in replicating associations in admixed populations.
Asthma; genetic risk factors; meta-analysis; KLK3
Daily inhaled glucocorticoids are recommended for young children at risk for asthma exacerbations, as indicated by a positive value on the modified asthma predictive index (API) and an exacerbation in the preceding year, but concern remains about daily adherence and effects on growth. We compared daily therapy with intermittent therapy.
We studied 278 children between the ages of 12 and 53 months who had positive values on the modified API, recurrent wheezing episodes, and at least one exacerbation in the previous year but a low degree of impairment. Children were randomly assigned to receive a budesonide inhalation suspension for 1 year as either an intermittent high-dose regimen (1 mg twice daily for 7 days, starting early during a predefined respiratory tract illness) or a daily low-dose regimen (0.5 mg nightly) with corresponding placebos. The primary outcome was the frequency of exacerbations requiring oral glucocorticoid therapy.
The daily regimen of budesonide did not differ significantly from the intermittent regimen with respect to the frequency of exacerbations, with a rate per patient-year for the daily regimen of 0.97 (95% confidence interval [CI], 0.76 to 1.22) versus a rate of 0.95 (95% CI, 0.75 to 1.20) for the intermittent regimen (relative rate in the intermittent-regimen group, 0.99; 95% CI, 0.71 to 1.35; P=0.60). There were also no significant between-group differences in several other measures of asthma severity, including the time to the first exacerbation, or adverse events. The mean exposure to budesonide was 104 mg less with the intermittent regimen than with the daily regimen.
A daily low-dose regimen of budesonide was not superior to an intermittent high-dose regimen in reducing asthma exacerbations. Daily administration led to greater exposure to the drug at 1 year.
Cost-effectiveness analyses of asthma controller regimens for adults exist, but similar evaluations exclusively for children are few.
To compare the cost-effectiveness of two commonly used asthma controllers, fluticasone and montelukast, with data from the Pediatric Asthma Controller Trial.
We compared the cost-effectiveness of low-dose fluticasone with montelukast in a randomized controlled multi-center clinical trial in children with mild-moderate persistent asthma. Analyses were also conducted on subgroups based on phenotypic factors. Effectiveness measures included a) the number of asthma-control days, b) the percentage of participants with an increase over baseline of FEV1≥12%, and c) the number of exacerbations avoided. Costs were analyzed from both a US health care payer's perspective and a societal perspective.
For all cost-effectiveness measures studied, fluticasone cost less and was more effective than montelukast; e.g., fluticasone treatment cost $430 less in mean direct cost (P<0.01) and had 40 more asthma control days (P<0.01) during the 48 week study period. Considering sampling uncertainty, fluticasone cost less and was more effective at least 95% of the time. For the high eNO phenotypic subgroup (eNO≥25ppb) and more responsive PC20 subgroup (PC20<2 mg/mL), fluticasone was cost-effective compared with montelukast for all cost-effectiveness measures; whereas not all the effectiveness measures were statistically different for the other two phenotypic subgroups.
For children with mild-moderate persistent asthma, low dose fluticasone had lower cost and higher effectiveness compared with montelukast, especially in those with more airway inflammation as indicated by elevated levels of eNO and more responsivity to methacholine.
Cost-effectiveness analysis; childhood asthma; fluticasone; montelukast; PACT
human rhinovirus; respiratory syncytial virus; wheezing; asthma; children; interferons
Viral respiratory tract infections are frequent and usually self-limited illnesses. For patients at risk for asthma, or with existing asthma, viral respiratory tract infections can have a profound effect on the expression of disease or loss of control. New evidence has shown that wheezing episodes early in life with the common cold virus, human rhinovirus, is a major risk factor for the later diagnosis of asthma at age six years. For those with existing asthma, exacerbations are a major cause of morbidity, need for acute care and, rarely, death. Viral respiratory tract infections, most frequently with rhinovirus, are the predominant microorganisms associated with asthma exacerbations. Evidence is also emerging that deficiencies in antiviral activity and the integrity of the airway epithelial barrier may make individuals with asthma more likely to have severe viral respiratory infections of the lower airway, and thus increase the risk of exacerbation. Given the influences of respiratory viruses on many aspects of asthma, efforts to understand the mechanisms and risk factors by which these airway infections cause changes in airway pathophysiology are a first step in improved treatment.
The assumption that the assessment of FEF25-75 does not provide additional information in asthmatic children with normal FEV1 % predicted has not been adequately tested.
To determine whether the measurement of the FEF25-75 % predicted offers advantages over the FEV1 % predicted and the FEV1/FVC % predicted for the evaluation of childhood asthma.
Methods and Measurements
This is a secondary analysis of data from the “Pediatric Asthma Controller Trial” and the “Characterizing the Response to a Leukotriene Receptor Antagonist and Inhaled Corticosteroid” trials. Pearson correlation coefficients, Pearson partial correlation coefficients, canonical correlations, and receiver operator characteristic (ROC) curves were constructed.
Among 437 children with normal FEV1 % predicted, FEF25-75 % predicted and FEV1/FVC % predicted were (1) positively correlated with log2 methacholine PC20, (2) positively correlated with morning and evening peak expiratory flow % predicted, and (3) negatively correlated with log10 FeNO and bronchodilator responsiveness. Pearson partial correlations and canonical correlations indicated that FEF25-75 % predicted was better correlated with bronchodilator responsiveness and log2 methacholine PC20 than were the FEV1 % predicted or FEV1/FVC % predicted. In the ROC curve analysis, FEF25-75 at 65% predicted had a 90% sensitivity and a 67% specificity for detecting a 20% increase in FEV1 following albuterol inhalation.
FEF25-75 % predicted was well correlated with bronchodilator responsiveness in asthmatic children with normal FEV1. FEF25-75 % predicted should be evaluated in clinical studies of asthma in children, and may be of use in predicting the presence of clinically relevant reversible airflow obstruction.
FEF25-75; bronchodilator responsiveness; asthma; FEV1/FVC; canonical correlations and ROC curves
IgE plays an essential role in type I allergy, however there is less information about the relationship between other immunoglobulins (IgA and IgG) and atopic phenotypes in early childhood.
We hypothesized that levels of circulating IgA in early childhood would be inversely related to the number of respiratory infections and the risk of becoming sensitized to allergens.
Immunoglobulin levels were analyzed (ELISA) in plasma samples (IgG, IgA), and in nasal secretions (IgA) from children participating in a high-risk birth cohort study. Samples were available from 264 children at age 2 years and 257 children at age 4 years, and results were compared to rates of respiratory illnesses, allergic sensitization, atopic dermatitis, and asthma.
Children who were sensitized to allergens had higher rather than lower levels of circulating IgA. A subgroup analysis showed that IgA levels were increased in relationship to foods sensitization (58 vs. 50 mg/dL, p = 0.003) but not aeroallergen sensitization (52 vs. 53 mg/dL, p = 0.11). IgA levels in the plasma correlated with levels of IgE levels (rs=0.19, p=0.003). Levels of IgE, but not IgG or IgA, were positively correlated with rates of respiratory illnesses, atopic dermatitis, and the risk of developing asthma. Finally, there were no significant relationships between IgA in nasal secretions and infectious outcomes.
In conclusion, low-normal concentrations of plasma IgA are associated with a reduced prevalence of allergic sensitization in infancy. Further, levels of IgA and IgG in plasma within the range of normal, and IgA in nasal secretions, do not appear to influence the risk of subsequent respiratory illnesses. Further studies to define relationships between IgA and allergic sensitization are likely to provide new insights into the pathogenesis of allergic diseases in infancy.
IgA; IgE; respiratory illnesses; allergy; infants
Exacerbations of childhood asthma and rhinovirus infections both peak during the spring and fall, suggesting that viral infections are major contributors to seasonal asthma morbidity.
To evaluate rhinovirus infections during peak seasons in children with asthma, and to analyze relationships between viral infection and illness severity.
Fifty-eight children with asthma ages 6-8 years provided 5 consecutive weekly nasal lavage samples during September and April; symptoms, medication use, and peak flow were recorded. Rhinoviruses were identified using multiplex PCR and partial sequencing of viral genomes.
Viruses were detected in 36-50% of the specimens, and, 72-99% of the viruses were rhinoviruses. There were 52 different strains (including 16 HRV-C) among the 169 rhinovirus isolates; no strains found in more than two collection periods, and all but two children had a respiratory infection. Virus-positive weeks were associated with greater cold and asthma severity (p<0.0001 and p=0.0002 respectively). Furthermore, virus-positive illnesses had increased duration and severity of cold and asthma symptoms, and more frequent loss of asthma control (47% vs. 22%, p=0.008). While allergen-sensitized vs. non-sensitized children had the same number of viral infections, the former had 47% more symptomatic viral illnesses (1.19 vs. 0.81 per month, p=0.03).
Rhinovirus infections are nearly universal in children with asthma during common cold seasons, likely due to a plethora of new strains appearing each season. Illnesses associated with viruses have greater duration and severity. Finally, atopic asthmatic children experienced more frequent and severe viral-induced illnesses.
The combination of viral infection and allergy increases the morbidity of respiratory illness in children with asthma.
asthma; children; viral respiratory tract infection; human rhinovirus; allergic sensitization; wheezing; cold symptoms; illness
For children who have uncontrolled asthma despite the use of low-dose inhaled corticosteroids (ICS), evidence to guide step-up therapy is lacking.
We randomly assigned 182 children (6 to 17 years of age), who had uncontrolled asthma while receiving 100 µg of fluticasone twice daily, to receive each of three blinded step-up therapies in random order for 16 weeks: 250 µg of fluticasone twice daily (ICS step-up), 100 µg of fluticasone plus 50 µg of a long-acting beta-agonist twice daily (LABA step-up), or 100 µg of fluticasone twice daily plus 5 or 10 mg of a leukotriene-receptor antagonist daily (LTRA step-up). We used a triple-crossover design and a composite of three outcomes (exacerbations, asthma-control days, and the forced expiratory volume in 1 second) to determine whether the frequency of a differential response to the step-up regimens was more than 25%.
A differential response occurred in 161 of 165 patients who were evaluated (P<0.001). The response to LABA step-up therapy was most likely to be the best response, as compared with responses to LTRA step-up (relative probability, 1.6; 95% confidence interval [CI], 1.1 to 2.3; P = 0.004) and ICS step-up (relative probability, 1.7; 95% CI, 1.2 to 2.4; P = 0.002). Higher scores on the Asthma Control Test before randomization (indicating better control at baseline) predicted a better response to LABA step-up (P = 0.009). White race predicted a better response to LABA step-up, whereas black patients were least likely to have a best response to LTRA step-up (P = 0.005).
Nearly all the children had a differential response to each step-up therapy. LABA step-up was significantly more likely to provide the best response than either ICS or LTRA step-up. However, many children had a best response to ICS or LTRA step-up therapy, highlighting the need to regularly monitor and appropriately adjust each child’s asthma therapy. (ClinicalTrials.gov number, NCT00395304.)