The relationship between infant lung function and the risk of wheeze in the preschool years

RATIONALE

There is evidence that perinatal lung development predicts childhood wheeze. However, very few studies have examined whether preschool wheeze is associated with lower premorbid lung function in early infancy, and as yet there is no information relating atopic and non-atopic preschool wheeze to early lung development.

OBJECTIVE

To examine the association between premorbid infant lung function and preschool wheeze, and to explore associations with atopic and non-atopic wheeze phenotypes.

METHODS

Infant lung function was measured in 147 healthy term infants aged 5-14 weeks. Rapid thoracoabdominal compression was performed during tidal breathing and at raised volume to measure maximal expiratory flow at functional residual capacity (V' max FRC) and forced expiratory volume in 0.4 sec (FEV(0.4)). Atopic status was determined by skin prick testing at 3 years and wheeze ascertained from parental questionnaires (1 and 3 years).

MEASUREMENTS AND MAIN RESULTS

Lower early infancy V' max FRC was associated with wheeze in both the first and third years of life (P=0.002 and 0.006, respectively). Lower early infancy FEV(0.4) was associated with wheeze in the first year (P=0.03). Compared to non-atopic children who did not wheeze, non-atopic children who wheezed in their third year of life had lower FEV(0.4) (P=0.02), while FEV(0.4) values of atopic children who wheezed were not significantly different (P=0.4).

CONCLUSIONS

Lower premorbid infant lung function was present in infants who subsequently wheezed during the first and third years of life. Lower FEV(0.4) in early infancy was associated with non-atopic wheeze but not atopic wheeze at 3 years of age.

Genetic association studies of interleukin-13 receptor alpha1 subunit gene polymorphisms in asthma and atopy

Interleukin (IL)-13 plays a central role in asthma pathogenesis by binding to the IL-13 receptor, which is a heterodimer composed of the IL-13 receptor alpha1 subunit (IL-13Ralpha1) and IL-4Ralpha. The genetic diversity at the IL-13Ralpha1 gene (IL13RA1) locus on chromosome Xq24 was characterised and the association of identified polymorphisms with asthma and atopy phenotypes examined. The promoter and coding region of IL13RA1 were screened for common genetic variants, and polymorphisms found were genotyped in a large cohort of 341 asthmatic Caucasian families (each containing at least two asthmatic siblings) and 182 nonasthmatic control subjects. Genetic association was determined using case-control and transmission disequilibrium test analyses. Two common polymorphisms were identified, a newly found thymidine (T) to guanine (G) transition of nucleotide -281 (-281T>G) single nucleotide polymorphism in the IL13RA1 promoter and the previously described 1365A>G variant in the IL13RA1 proximal 3' untranslated region. No significant association of either -281T>G or 1365A>G with risk of asthma or atopy phenotypes was found, apart from a suggestive association between the IL13RA1 -281T/1365A haplotype and raised total serum immunoglobulin E levels in adult female asthmatics. These findings indicate that the interleukin-13 receptor alpha1 subunit gene -281T>G and 1365A>G polymorphisms do not contribute to asthma susceptibility or severity, although the interleukin-13 receptor alpha1 subunit gene locus might be involved in the control of immunoglobulin E production.

Polymorphism of the mast cell chymase gene (CMA1) promoter region: lack of association with asthma but association with serum total immunoglobulin E levels in adult atopic dermatitis

BACKGROUND

Mast cell chymase has the potential to be an important mediator of inflammation and remodelling in the asthmatic lung. Previous studies have examined association between promoter polymorphism of the chymase gene (CMA1) and allergic phenotypes but the significance of this polymorphism is unclear. We have examined association of a CMA1 variant in relation to asthma in a large UK Caucasian family cohort.

METHODS

A polymorphism of the CMA1 gene promoter (-1903G/A) was genotyped in 341 asthmatic families and in 184 non-asthmatic adults recruited from the UK PCR-RFLP based genotyping. Association with asthma diagnosis, atopy, specific and total IgE, and atopy and asthma severity was examined.

RESULTS

Case-control studies did not reveal a significant difference in allele frequency between asthmatics and controls. A significant association was found between CMA1 genotypes and total IgE levels in subjects with self-reported eczema that remained significant after correction for multiple testing (median total serum IgE GG 297 kU/L, GA 144 kU/L, AA 48.4 kU/L, Pc=0.0032).

CONCLUSION

These data suggest that CMA1 promoter polymorphism does not contribute to asthma susceptibility or severity but may be involved in regulating IgE levels in patients with eczema.

Toll-like receptor 4 polymorphism and severity of atopy in asthmatics

Endotoxin exposure may have a protective effect against asthma and atopy. An Asp299Gly polymorphism in the Toll-like receptor 4 (TLR4) gene reduces responsiveness to endotoxin. This study determined the effect of TLR4 polymorphism on the risk and severity of asthma and atopy. In all, 336 UK Caucasian families with > or = 2 affected sibs (physician's diagnosis of asthma and current medication use) and 179 Caucasians without asthma or a family history of asthma were genotyped using ARMS-PCR. No association of the TLR4 polymorphism was found with the risk of developing asthma, either in parent-affected sibling trios, or in case-control analyses (P>0.05). In the first affected asthmatic siblings, the atopy severity score (based on size and number of positive skin-prick tests and specific IgE) was higher in those with the Asp/Gly or Gly/Gly genotypes (mean 1.8, s.d. 1.1, n=39) compared to those with the Asp/Asp genotype (mean 1.2, s.d. 1.0, n=279) (P=0.003, t-test). No associations were found with total IgE, FEV(1) % predicted, slope of FEV(1) response to methacholine or asthma severity score (P>0.05). This study confirms the previously observed lack of association of TLR4 polymorphisms with asthma. In contrast, the findings suggest that genetically determined hyporesponsiveness to endotoxin may increase atopy severity.

Promoter polymorphism in the 5-lipoxygenase (ALOX5) and 5-lipoxygenase-activating protein (ALOX5AP) genes and asthma susceptibility in a Caucasian population

BACKGROUND

5-Lipoxygenase (5-LO) and 5-lipoxygenase-activating protein (FLAP) are essential for cysteinyl-leukotriene (cys-LT) production, critical mediators in asthma.

OBJECTIVE

We sought to identify novel promoter polymorphisms within the FLAP (ALOX5AP) gene promoter and test the role of these and the previously identified 5-LO (ALOX5) Sp1 promoter polymorphism in asthma susceptibility.

METHODS

To assess genetic association with asthma phenotypes, we genotyped 341 Caucasian families (containing two asthmatic siblings) and non-asthmatic control subjects (n=184). Genetic association was determined by case-control and transmission disequilibrium test (TDT) analyses. To determine the functional role of polymorphisms on basal transcription, we generated ALOX5AP-promoter-luciferase constructs and transiently transfected human HeLa cells.

RESULTS

A novel G/A substitution at -336 bp and a poly(A) repeat (n=19 or 23) at position -169 to -146 bp were identified in the ALOX5AP promoter. Genotyping found the -336 A and poly(A19) alleles at frequencies of q=0.06 and 0.12, respectively. No ALOX5AP allele was associated with asthma or asthma-related phenotypes in case-control or TDT analyses. ALOX5AP-promoter-luciferase analyses did not support a functional role of the -336 or poly(A) polymorphism in determining basal transcription. The ALOX5 Sp1 polymorphism was predominantly homozygous wild-type 5/5 (frequency q=0.70) and heterozygous 4/5 (q=0.23) genotypes and no allele was associated with asthma or asthma-related phenotypes.

CONCLUSION

Taken together, these data do not support a significant role for these polymorphisms in genetic susceptibility to asthma in the Caucasian population.

Polymorphisms in the interleukin-4 and interleukin-4 receptor alpha chain genes confer susceptibility to asthma and atopy in a Caucasian population

BACKGROUND

IL-4 by binding to its receptor (IL-4R) is essential for the development of airway inflammation present in asthma, through the induction of IgE synthesis in B cells and differentiation of T cells to a Th2 phenotype.

OBJECTIVE

To investigate the role of four common polymorphisms in the IL-4 (IL4-34CT and IL4-589CT) and IL-4Ralpha chain (IL4RAI50V and IL4RAQ576R) genes in conferring susceptibility to the development of atopy and/or asthma.

METHODS

Two polymorphisms in the IL-4 gene promoter, IL4-34CT and IL4-589CT, and two polymorphisms in the IL-4Ralpha chain gene, IL4RAI50V and IL4RAQ576R, have been genotyped using PCR-based methods in 341 asthmatic families and in 184 non-asthmatic adults recruited from the south of England.

RESULTS

Case-control analysis did not reveal differences in the distribution of the four polymorphisms between asthmatics and controls. However, the transmission disequilibrium test showed that the IL4-589 T allele was preferentially transmitted to asthmatic children (P=0.036) and that the IL4RAQ576 was preferentially transmitted to children with atopic asthma (P=0.018). Haplotype analysis showed a strong association between the IL4-34T/-589T haplotype and asthma per se (P=0.041), and a strong association between the IL4RA I50/Q576 haplotype and atopic asthma (P=0.006).

CONCLUSION

Our data suggest that polymorphisms in the IL-4 and IL-4Ralpha chain genes might play a role both conferring susceptibility to and modulating severity of atopy and asthma.

Allelic association and functional studies of promoter polymorphism in the leukotriene C4 synthase gene (LTC4S) in asthma

BACKGROUND

LTC4 synthase is essential for the production of cysteinyl leukotrienes (Cys-LT), critical mediators in asthma. We have identified a novel promoter polymorphism at position -1072 (G/A) and a -444 (A/C) polymorphism has previously been reported. The role of these polymorphisms in the genetic susceptibility to asthma was examined.

METHODS

To test for genetic association with asthma phenotypes, 341 white families (two asthmatic siblings) and 184 non-asthmatic control subjects were genotyped. Genetic association was assessed using case control and transmission disequilibrium test (TDT) analyses. LTC4S promoter luciferase constructs and transiently transfected human HeLa and KU812F cells were generated to determine the functional role of these polymorphisms on basal transcription.

RESULTS

No associations were observed in case control analyses (-1072 A, q=0.09; -444 C, q=0.29); the TDT identified a borderline association between the -444 C allele and bronchial responsiveness to methacholine (p=0.065). Asthmatic children with the -444 C allele had a lower mean basal forced expiratory volume in 1 second (97.4 v 92.7% predicted, p=0.005). LTC4S promoter luciferase analyses provided no evidence for a functional role of either polymorphism in determining basal transcription.

CONCLUSION

This study does not support a role for these polymorphisms in genetic susceptibility to asthma but provides evidence to suggest a role in determining lung function parameters.

Measuring lung function in infancy

Although the earliest reliable lung function tests in infants were performed as long as 40 years ago, there has only recently been a growth in this area, as simpler methods and better equipment and IT resources have been developed. Exciting information is accumulating about the normal physiology and pathology of the infant lung. Many basic questions are still unanswered and the ability to perform these tests remains confined to a few specialized centres. To co-ordinate the development of ILFT and establish standardization in a number of areas including measurement conditions, equipment specifications, methodology protocols and data analysis, international collaboration is necessary between the teams working in this field (Table 5). Collaborative groups are currently addressing these issues and are also developing recommendations regarding the design of randomized clinical trials, multi-centre studies and research agendas. Infant lung function testing remains primarily a research tool. Our aim should be not only to refine and develop the techniques of physiological measurement but to apply ILFT to the objective study of respiratory illness in infants in the clinical setting so as to aid in the prevention and treatment of these common, debilitating and costly diseases.

Smoking habits in a cohort of U.K. adolescents

Active smoking is an increasing problem amongst U.K. teenagers. The smoking habits of a cohort of 14-16-year-olds were determined and the association between regular active smoking and domestic and social factors investigated. Current smoking habits of a cohort of 2289 14-16-year-olds were assessed using a simple postal questionnaire. Data concerning potential factors associated with active smoking were collected from questionnaire completed by parents. Nine hundred and sixty-nine (44.8%) children admitted to having smoked at some time, with 562 (30.0%) having smoked in the previous 12 months. Three hundred and six (14.1%) children were regular smokers and 158 (51.6% of regular smokers, 7.3% of total cohort) smoked daily. Age, number of other children in the household, parental smoking, smoking sibling(s) and living in a single parent household were all independently associated with regular smoking. Regular smoking was a significant problem amongst this cohort of teenagers. Living with other smokers, age, household size and living with one parent all predicted a regular smoking habit.

Measuring pulmonary function in infancy

In recent years there has been a growing interest in the measurement of pulmonary function in infants for both clinical and research purposes. Such measurements remain limited by the complexity of the equipment as well as by the technical and physiological challenges of testing infants and neonates. Despite these problems, assessment of respiratory function in early life provides exciting information about the post-natal growth and development of lungs in health and disease. The aim of this paper is to discuss the physiological, technical and ethical problems surrounding these procedures, as well as reviewing the current methods of testing pulmonary function in the very young. Consideration is given to the developments needed if infant pulmonary function tests are to realise fully, their potential as research and clinical tools.

Issues in understanding childhood asthma

Asthma and related allergic disorders in childhood have increased considerably in prevalence over the last few decades. During the same period of increasing morbidity from childhood asthma in the community, there have been dramatic advances in understanding of the basic immunopathologic features of the disease and consequently the development of a far more rational approach to its treatment. The immunopathologic condition of eosinophil-mediated airway inflammation is established very early in the evolution of asthma in childhood. It may even antedate the onset of symptoms. The present state of the art dictates that early intervention with potent therapies cannot be justified on the basis of symptoms alone and may in any case have no influence on the natural history of the condition. This means that current cautious therapeutic guidelines should continue to be followed. However, with the development of more accurate markers predicting ongoing disease, it will be possible to evaluate a whole range of early interventions in the future. Much evidence, though indirect, points to the possibility that the only true prophylaxis that will affect the natural history of asthma will need to be commenced before clinical features are manifest.

Progression from allergic sensitization to asthma

Asthma is one of the atopic diseases strongly associated with allergy. High aeroallergen exposure in the immediate postnatal period has been associated with higher risk of sensitization and chronic asthma. It is proposed that following in utero allergen sensitization, postnatal high dose allergen exposure localizes inflammation to the airways. In association with adjuvantizing effects of some virus infections, eosinophils and neutrophils are recruited which contribute to epithelial damage and the initiation of the remodelling process. Eventually, the latter processes lead to sufficient airway narrowing to manifest as the first symptoms of asthma. Thus, the immunopathology of asthma is fully established by the time of first symptoms and future strategies will need to identify those at risk of developing the disease before irreversible changes in the airways are established.

Can we predict which wheezy infants will continue to wheeze?

Early intervention strategies in infant wheezing will be dependent on the ability to predict persistence of disease. We undertook a prospective longitudinal study to determine which factors might be predictive for the persistence of wheeze. We examined a group of 107 children 3 to 36 mo of age with at least one atopic parent. Children were recruited within 12 wk of first wheeze. Factors assessed included: personal atopy (IgE > 1 SD above age-related normal and/or eczema and/or positive skin tests); parental atopy; number of siblings; age at first wheeze; sex; serum-soluble IL-2R; proliferation of peripheral blood mononuclear cells (PBMC) to beta-lactoglobulin and to D. pteronyssinus; production of IFN-gamma on stimulation of PBMC with beta-lactoglobulin and with D. pteronyssinus. A positive clinical outcome (child requiring prophylactic antiasthma treatment after 1 yr) was observed in 53 (49.5%) children. Predictor variables were assessed by univariate and multivariate logistic regression. Wheeze was more likely to be persistent in older, atopic children with biparental atopy. The model offering best prediction of persistent wheeze with least risk of including asymptomatic subjects was age at presentation + sIL-2R. Trials of early intervention strategies using a logistic regression equation based on this model for patient recruitment can now be designed.

Asthma survey items as predictors of respiratory problems in children 2 yrs later: a longitudinal study

The study compared the ability of characteristics defined by an asthma survey (wheeze versus cough and asthma diagnosis versus no diagnosis) to predict later respiratory problems in a cohort of 108 schoolchildren who had reported either recent wheeze or recurrent cough in a 1987 asthma survey. The children recorded daily respiratory symptoms and peak flow from April 1989 until May 1990. The frequency and severity of lower respiratory symptom episodes and peak flow dips were compared in the wheeze and cough groups and in the diagnosed versus nondiagnosed children. The independent effects of initial wheeze, atopy, diagnosis and bronchial hyperresponsiveness (BHR) on the longitudinal outcome measures were assessed using multiple linear regression. Children with initial wheeze had more chronic symptoms and peak flow variability than those with cough alone, but wheeze had only a weak effect on frequency and severity of acute lower respiratory episodes. Children with both wheeze and atopy had more acute symptomatic episodes and more chronic symptoms than did the other children. Children with diagnosed asthma (versus no diagnosis) had significantly more frequent and severe lower respiratory exacerbations, more days symptomatic and greater peak flow variability. The predictive effects of diagnosis were independent of (and stronger than the effects of) wheeze, atopy and BHR, or combinations of these variables. The results suggest that among children who report respiratory symptoms, survey-reported wheeze on its own is a weaker marker of significant respiratory disease than is a doctor's diagnosis of asthma.

A single-blind, placebo-controlled trial of a simple acupuncture treatment in the cessation of smoking

BACKGROUND

Tobacco smoking is a major cause of preventable disease and premature death. Physicians should play an active role in the control of smoking by encouraging cessation and helping the smoker to choose the most suitable aid to cessation.

AIM

To evaluate a simple, ear acupuncture treatment for the cessation of smoking.

METHOD

Randomized, single-blind, placebo-controlled trial of 78 currently smoking volunteers from the general public. Volunteers attended an acupuncture clinic in a general practice setting and were given a single treatment of electroacupuncture using two needles at either an active or a placebo site plus self-retained ear seeds for two weeks. The major outcome measure was biochemically validated total cessation of smoking at six months.

RESULTS

A total of 12.5% of the active treatment group compared with 0% of the placebo group ceased smoking at six months (P = 0.055, 95% confidence interval -0.033 to 0.323).

CONCLUSION

This simple ear electroacupuncture treatment was significantly more effective in helping volunteers to quit smoking than placebo treatment.

The natural history of respiratory symptoms in a cohort of adolescents

A cohort of 2,289 children, previously studied at the age of 6-8 yr, were followed up by means of a postal questionnaire when aged 14 -16 yr to examine the association between potential risk factors and the natural history of respiratory symptoms. Children with current symptoms, persistent symptoms, and late-onset symptoms were identified and multivariate analyses were performed to determine the independent association between risk factors and these various symptom-based subgroups. Personal and family history of atopy was significantly associated with all symptom groups and with the presence of doctor-diagnosed asthma. Smoking, either active or passive, was shown to be significantly associated with current, persistent, and late-onset symptoms. Other factors shown to be significantly associated with certain symptom groups were gender (late-onset wheeze), single-parent households (current cough, persistent cough), social class (late-onset wheeze), number of children in the household (persistent wheeze, late-onset cough), number of furry pets in the household (current wheeze), birth weight (late-onset wheeze), and gas cookers (current wheeze, persistent wheeze). In a subgroup of children studied in more detail in 1987, bronchial hyperresponsiveness in 1987 was positively associated with persistent wheeze in 1995, whereas positive skin-prick testing in 1987 was not.

Phenotype stability in asthma and atopy in childhood

The asthma phenotype can be described using a combination of the following: symptom type, pattern and severity; markers of atopy; and measurement of bronchial responsiveness. Because of the very nature of the disease, symptoms of asthma are variable in both the short-and the long-term, and the natural history of the disease is such that symptoms in an individual may evolve over time through different patterns. Although atopy appears to be a life-long attribute resulting from an early life switching to a TH2 immune response, the surrogate markers of atopy each are subject to their own time-related determinants and patterns of change with age. Bronchial responsiveness in childhood is neither specific nor sensitive for asthma, and although showing good short-term repeatability, can vary widely when measured over a period of months or years. Stimuli for responsiveness testing should be chosen which can be inhaled safely in high doses so as to allow an end point to be reached by as many subjects within a population as possible, and individuals may have to be tested repeatedly over time so as to avoid misclassification.

Youth attitudes toward guns and violence: relations with sex, age, ethnic group, and firearm exposure

Investigated relations between young people's scores on the Attitudes Toward Guns and Violence Questionnaire (AGVQ; Shapiro, Dorman, Burkey, Welker, & Clough, 1997), demographic variables, and exposure to firearms and violence. 1,164 students, Grades 3 to 12, from an urban, suburban, parochial, and private school system completed anonymous self-report questionnaires in their classrooms. Boys produced higher AGVQ scores than did girls. Scores were similar in Grades 3 and 5, were much higher in Grade 6 than in Grade 5, and were similar in Grades 6 and above. This pattern was found across sex, race, and school system. African Americans obtained higher scores than Caucasians on the AGVQ and on 2 of its 4 factors. Students in the urban public schools produced higher scores than did youth in the other school systems. Both traumatic and nontraumatic exposure to firearms were associated with high AGVQ scores. Sex, grade, and firearm exposure were associated with relatively large differences, while ethnic group and school system were associated with relatively small differences.

Development and factor analysis of a measure of youth attitudes toward guns and violence

Administered the Attitudes Toward Guns and Violence Questionnaire (AGVQ) to 1,619 students in Grades 3, 5, 6, 7, 9, 11, and 12 from four demographically diverse school systems. Fifty-two of the 61 items exhibited satisfactory part-whole correlation and correlation with a validity criterion. Factor analysis revealed four main factors: Aggressive Response to Shame, Comfort With Aggression, Excitement, and Power/Safety. The instrument was reduced to 23 items by deleting items with high cross-loadings. Construct validity was similar for the longer and shorter versions. Youth who self-reported owning a gun produced scores 1.5 SD higher than nonowners. Low scores were associated with a 1 in 125 chance of gun ownership, and high scores were associated with a 1 in 3 chance. Congruency coefficients indicated similar factor structure for the present sample and a separate sample of 5th-, 7th- and 9th-grade students. These results indicate that the AGVQ is a reliable and valid measure of violence-related attitudes in young people.

Development and factor analysis of a measure of youth attitudes toward guns and violence

Administered the Attitudes Toward Guns and Violence Questionnaire (AGVQ) to 1,619 students in Grades 3, 5, 6, 7, 9, 11, and 12 from four demographically diverse school systems. Fifty-two of the 61 items exhibited satisfactory part-whole correlation and correlation with a validity criterion. Factor analysis revealed four main factors: Aggressive Response to Shame, Comfort With Aggression, Excitement, and Power/Safety. The instrument was reduced to 23 items by deleting items with high cross-loadings. Construct validity was similar for the longer and shorter versions. Youth who self-reported owning a gun produced scores 1.5 SD higher than nonowners. Low scores were associated with a 1 in 125 chance of gun ownership, and high scores were associated with a 1 in 3 chance. Congruency coefficients indicated similar factor structure for the present sample and a separate sample of 5th-, 7th- and 9th-grade students. These results indicate that the AGVQ is a reliable and valid measure of violence-related attitudes in young people.

The effects of inhaled beclomethasone dipropionate on lung function and histamine responsiveness in recurrently wheezy infants

Inhaled steroids improve pulmonary function and bronchial responsiveness in older asthmatics. Data from studies using subjective outcome measures to determine the effectiveness of inhaled steroids in infants with recurrent wheezing are equivocal. Therefore, this study tested the hypothesis that beclomethasone dipropionate improves pulmonary function, including bronchial responsiveness to histamine, in recurrently wheezy infants. The study was double blind, placebo controlled lasting nine weeks. After the first baseline week, pulmonary function was measured using the rapid thoracoabdominal compression technique and bronchial responsiveness assessed with a histamine challenge test. Infants were then randomly allocated to receive doses of placebo or beclomethasone dipropionate (100 micrograms/puff) from metered aerosols. Two puffs of test aerosol were administered twice daily for eight weeks via a large volume spacer fitted with a facemask. Symptoms were recorded daily and pulmonary function and bronchial responsiveness assessed at the end of the treatment period; 50 infants, median age 12 months (range 5 to 18 months), were recruited. Twenty three in the beclomethasone dipropionate group and 15 in the placebo group completed the study and had pairs of pulmonary function measurements. Three were probable treatment failures (one beclomethasone dipropionate, two placebo), three were possible treatment failures (placebo), and others were non-compliant with study protocol. Baseline variables were not significantly different between those infants who completed the study and those who did not. Beclomethasone dipropionate and placebo groups were similar in all respects at baseline. Lung function and symptoms improved for both groups of infants during the study. Bronchial responsiveness increased significantly in the placebo group but there were not statistically significant differences between groups for any of the other outcome measures. It is concluded that beclomethasone dipropionate (400 microgram daily) via a large volume spacer does not significantly improve lung function or symptoms in recurrently wheezy infants but might hav a beneficial effect on bronchial responsiveness.

Association between lower respiratory tract symptoms and falls in peak expiratory flow in children

Peak expiratory flow (PEF) measurements are increasingly recommended in childhood asthma management. However, few data are available on the temporal relationship between the onset of upper and lower respiratory tract symptoms and significant falls in PEF. We wanted to determine whether falls in PEF constitute a sensitive marker for clinical episodes of respiratory morbidity. We therefore analysed data on daily PEF and respiratory symptom recording from a 12 month longitudinal study in 192 children aged 7 and 8 yrs with current respiratory symptoms. Outcome measures were number of and relationship between: 1) episodes of fall in PEF (defined as a fall in PEF for more than 2 days to < 1.5 SD below individual mean morning PEF); and 2) upper and lower respiratory tract symptom events (defined as a respiratory symptoms score of > 3 units within three consecutive days). One hundred and eight six of the 192 children completed the study. For the group as a whole, the mean number of PEF episodes per subject was 3.5, and the mean number of symptom events 8.9, with 29% of symptom events being temporally associated with a PEF episode, and 40% of PEF episodes not being accompanied by a symptom event. Forty nine percent of PEF episodes were preceded by at least two consecutive days of either upper or lower respiratory symptoms. We conclude that falls in PEF alone were not a sensitive marker for episodes of respiratory morbidity. On almost half of the occasions where PEF did fall, morbidity could have been detected at least 2 days earlier using symptom reporting.(ABSTRACT TRUNCATED AT 250 WORDS)

Association between lower respiratory tract symptoms and falls in peak expiratory flow in children

Peak expiratory flow (PEF) measurements are increasingly recommended in childhood asthma management. However, few data are available on the temporal relationship between the onset of upper and lower respiratory tract symptoms and significant falls in PEF. We wanted to determine whether falls in PEF constitute a sensitive marker for clinical episodes of respiratory morbidity. We therefore analysed data on daily PEF and respiratory symptom recording from a 12 month longitudinal study in 192 children aged 7 and 8 yrs with current respiratory symptoms. Outcome measures were number of and relationship between: 1) episodes of fall in PEF (defined as a fall in PEF for more than 2 days to < 1.5 SD below individual mean morning PEF); and 2) upper and lower respiratory tract symptom events (defined as a respiratory symptoms score of > 3 units within three consecutive days). One hundred and eight six of the 192 children completed the study. For the group as a whole, the mean number of PEF episodes per subject was 3.5, and the mean number of symptom events 8.9, with 29% of symptom events being temporally associated with a PEF episode, and 40% of PEF episodes not being accompanied by a symptom event. Forty nine percent of PEF episodes were preceded by at least two consecutive days of either upper or lower respiratory symptoms. We conclude that falls in PEF alone were not a sensitive marker for episodes of respiratory morbidity. On almost half of the occasions where PEF did fall, morbidity could have been detected at least 2 days earlier using symptom reporting.(ABSTRACT TRUNCATED AT 250 WORDS)

Episodes of respiratory morbidity in children with cough and wheeze

An important feature of "asthma" in children is the occurrence of repeated episodes of airflow obstruction lasting days or weeks. In this 1-yr longitudinal study, we investigated the nature of these episodes and their relationship to other indices of asthma. A random sample of children aged 7 and 8 yr reporting either cough or wheeze was invited to attend for skin testing. Ninety-six atopic children, half with cough and half with wheeze, and 96 nonatopic children, again half with cough and half with wheeze, were selected to join a longitudinal study. All children recorded twice daily peak expiratory flow (PEF) measurements and a daily 10-point symptom score. One hundred eighty-three children (95.3%) successfully completed the study. Episodes of respiratory morbidity, defined as falls in PEF to less than 1.5 standard deviations (SD) below subject mean lasting for more than 2 days, were identified and the 642 resulting episodes examined. Episodes were more common in autumn and winter (p = 0.003 to 0.017). The mean number of episodes per child was 3.5 (range 0 to 8): 94 (51.4%) children experienced more than three episodes, 54 (30.0%) experiencing five or more. The average duration of episodes was 4.1 days (range 2 to 27 days), with 44 (24%) subjects demonstrating episodes of average duration of 5 days or more and 18 (10%) of greater than 7 days. Episodes were more severe in children with wheeze (p = 0.013) and slightly more frequent in those with cough alone (p < 0.05). Atopy had no effect on episode frequency, duration, or magnitude.

The effect of sustained positive airway pressure on derived cardiac output in children

It is well established that the improvement in gas exchange that occurs with positive pressure ventilation may come at the expense of a decrease in cardiac output and oxygen delivery. Clinical observation suggests that children and infants may be more resistant than adults to the falls in cardiac output induced by positive airway pressure. The aims of this study were to quantify the effect of a sustained increase in intrathoracic pressure on cardiac output and stroke volume, and to determine whether this change is age-related. Twenty-eight children undergoing general anaesthesia were studied. Cardiac output was derived using pulsed wave Doppler techniques at four different levels of sustained positive airway pressure, and stroke volume was calculated. The relationship between airway pressure and both cardiac output and stroke volume was examined using a general linear model which included age as a continuous variable. Cardiac output decreased with increasing levels of sustained positive airway pressure (P = 0.001). The fall in SV for a given airway pressure increased with increasing age (P = 0.02). The mechanisms responsible for the increase of the magnitude of the fall in stroke volume with age remain to be elucidated.

Genetic 'risk' for atopy is associated with delayed postnatal maturation of T-cell competence

Recent in vitro studies suggest that IgE production in adults is co-ordinately regulated by negative signals from gamma IFN-producing CD4+ T-helper-1 (TH-1) and positive signals from IL-4 producing (TH-2) T-cells. Additionally, seroepidemiological evidence has pinpointed infancy as the period of maximum lifetime risk for T-cell sensitization to ubiquitous environmental antigens. The present study sought to elucidate the relationship between these observations, by examination of CD4+ T-cell function in normal children and those genetically at 'high risk' for atopy, spanning the age range (up to 4 years) in which IgE responses to environmental allergens is typically manifest. Immunocompetent T-cell precursor frequencies (determined by cloning at limiting dilution) were markedly reduced in 'high risk' children relative to normals (0.53 +/- 0.29 vs 0.26 +/- 0.19; P = 0.0025). Consistent with reports from other laboratories employing bulk T-cell culture techniques, the gamma IFN producing capacity of CD4+ T-cell clones from both groups of children were markedly reduced relative to adults, and was lowest in the high risk group (P < 0.02). IL-4 production by CD4+ T-cell clones from the normal children was within the adult range, but again was significantly lower in the high risk group (P < 0.00005). This indicates that initial immune responses to environmental allergens in early childhood occur against a background of maturational 'deficiency' in CD4+ T-cell function, and suggests the possibility that variations in the rate of postnatal maturation of T-cell competence may be a contributing factor in the development of differing patterns of immunological responsiveness to environmental allergens.

Longitudinal changes in skin-prick test reactivity over 2 years in a population of schoolchildren with respiratory symptoms

As part of a larger epidemiological study, 114 children with respiratory symptoms, born between 1978 and 1980, were skin-prick tested to Dermatophagoides pteronyssinus (DP), mixed grass pollens (G) and cat dander (C), and to histamine and saline controls (Bencard, U.K.) using 1 mm prick-lancets (Dome/Hollister-Stier), between July and September 1987 and again in October 1989. A weal > or = 2 mm to one or more allergens was regarded as a positive result. Each child was tested by the same investigator on each occasion, using similar techniques. Three children were excluded from analysis as they had failed to respond to histamine testing on one of the two occasions. In 1987, of the 111 children analysed, 58 (52%) children were skin-test positive, and 53 (48%) skin-test negative, while in 1989 62 (56%) were positive and 49 (44%) negative. Twelve children (11%) changed status from negative to positive, while eight (7%) changed from positive to negative. For the group as a whole the percentage agreement between the results obtained 2 years apart was 82%. In comparison to previous studies a greater number of subjects in this population than expected changed atopic status. We therefore further examined the data from those who had changed status and classified as borderline those subjects with no difference in weal size of greater than 2 mm for any allergen between 1987 and 1989. Only five children then changed status from negative to positive, none from positive to negative and 15 demonstrated only borderline changes. The coefficients of repeatability for the 106 children who did not change status were 3.37 mm, 2.80 mm and 2.33 mm for D. pteronyssinus, mixed grass pollens and cat dander respectively. The good short-term repeatability of the testing method was demonstrated in a group of 29 similar children; the coefficients of repeatability were 0.38 mm for DP and G, and 0.72 mm for C. These data demonstrate that, in a population of children with respiratory symptoms, skin-prick testing within individuals is highly repeatable over the short term, but poorly repeatable over a 2 year period. However, the percentage agreement in skin-prick test status for the group as a whole was high (82%). While no child became unequivocally skin-test negative having been previously positive, a small number of children changed status from negative to unequivocally positive, suggesting a genuine but small (4%) increase in the prevalence of skin-test positivity in this population.

Profile of bronchial responsiveness in children with respiratory symptoms

A postal questionnaire inquiring into the presence of respiratory symptoms was sent to 3698 children aged 7 and 8 years. Those reporting either cough or wheeze were randomised, and a sample invited to attend for skin testing. A total of 192 symptomatic children, half of whom were atopic and half non-atopic, were randomly selected to enter the study. All children performed and recorded best of three peak expiratory flow measurements twice a day and completed a 10 point respiratory symptom score card each day for one year. They also recorded all treatment taken and made a note of relevant life events. Each child was seen monthly for general assessment and for measurement of nonspecific bronchial responsiveness to methacholine. Of the 192 children, 183 successfully completed the study. For six subjects 11 measurements of the provocation dose required to cause a 20% fall in forced expiratory volume in one second (PD20) were available for analysis and on the remaining 177, greater than or equal to 12 measurements. The prevalence and degree of bronchial hyper-responsiveness (PD20 less than 6.4 mumol) and its relationship to atopy was examined by comparing the percentage of members of each symptom group demonstrating bronchial hyper-responsiveness and the number of occasions on which they did so, and by comparison of minimum and median PD20 values. The range of bronchial responsiveness shown during the study period by each child was expressed as doubling doses of methacholine and compared between symptom groups. Atopy and wheeze were both independently associated with an increased prevalence and greater degree of bronchial hyper-responsiveness when compared with non-atopy and cough respectively, all differences being significant a the 0.001 level.. Thirty three per cent of subjects demonstrated a rnge of methacholine responsiveness of >4 and 13.4% of >6 doubling doses during one year.

Airway response to exercise and methacholine in children with respiratory symptoms

Thirty atopic and 30 non-atopic subjects were identified from a population of 7-8 year old children with current respiratory symptoms. The response of the airways to exercise and provocation by methacholine were compared. In these children, who had symptoms but were not necessarily asthmatic, there was no significant correlation between the two stimuli. The atopic children were, however, significantly more responsive than the non-atopic children to both. For the whole group, odds ratios derived for atopy and for an increased response to methacholine (expressed as a PD20--the dose that caused the forced expiratory volume in one second (FEV1) to fall by 20%--of less than 6.4 mumol/l), a positive exercise test (greater than 15% fall in FEV1), and the presence of asthma were 13.5, 3.3, and 21.0, respectively; that for positive response to methacholine and positive exercise challenge was 1.5. Thus though increased bronchial responsiveness to methacholine and exercise challenge are both associated with a diagnosis of asthma, the association between the two stimuli is complex, and supports the view that they reflect entirely different components of airways dysfunction.

Effect of atopy on the natural history of symptoms, peak expiratory flow, and bronchial responsiveness in 7- and 8-year-old children with cough and wheeze. A 12-month longitudinal study [published errarum appears in Am Rev Respir Dis 1992 Aug;146(2):540]

Recurrent lower respiratory tract symptoms are common and disabling in childhood, but little is known of their natural history and relationship to asthma. We report a 12-month longitudinal study designed to determine the influence of atopy on respiratory symptoms and bronchial responsiveness in 7- and 8-yr-old children. A postal questionnaire inquiring into the presence of respiratory symptoms was sent to 3,698 children aged 7 and 8 yr. Those reporting either current wheeze (14.8%) or current cough in the absence of wheeze (12.8%) were randomized, and a sample was invited to attend for skin testing. The following groups of symptomatic children entered the longitudinal study: 48 atopic children with cough, 48 atopic children with wheeze, 48 nonatopic children with cough, and 48 nonatopic children with wheeze. All children recorded twice daily the best of three peak expiratory flow (PEF) measurements and completed a 10-point symptom score card, each day for 1 yr. They also recorded all treatment taken and made a note of relevant life events. Each child was seen monthly for general assessment and for measurement of methacholine bronchial responsiveness. Despite the arduous nature of the study 183 of the 192 children (95.3%) successfully completed the 12 months of observation. Symptom groups were compared with regard to FEV1, bronchial responsiveness, symptom chronicity and severity, and diurnal and day-to-day variation in PEF. Atopy was associated with a lower FEV1, increased prevalence of bronchial hyperresponsiveness, greater within-day and between-day variation in PEF, and greater severity of respiratory symptoms compared with the absence of atopy. Wheeze was associated with lower FEV1, increased prevalence of bronchial hyperresponsiveness, greater within-day and between-day variation in PEF1 and greater severity of respiratory symptoms compared with cough [corrected].