The interrelationship among bronchial hyperresponsiveness, the diagnosis of asthma, and asthma symptoms

Use of aerosols for bronchial provocation testing in the laboratory: where we have been and where we are going

Bronchial provocation testing with pharmacological agents that act directly on airway smooth muscle has important limitations. These include the inability to identify exercise-induced asthma (EIA), to differentiate the airway hyperresponsiveness (AHR) of airway remodelling from the AHR of active inflammation and to differentiate between doses of steroids. Recent studies show that tests that act indirectly to narrow airways are more sensitive than pharmacological agents for identifying airway inflammation and response to treatment. Adenosine monophosphate (AMP) is an indirect challenge that acts on mast cells to cause release of mediators. Hypertonic saline is another and, since its development in the 1980s, has become widely used in Australia. Hypertonic (4.5%) saline is used to identify those with active asthma, those with EIA and those who wish to enter certain occupations or sports (e.g., diving). The recent development, again in Australia, of a test that uses dry powder mannitol has promise for use in the laboratory, the office, or for testing in the field. AHR to mannitol identifies people with EIA and is an estimate of its severity. The mannitol response is modified by drugs used to prevent EIA, implying that similar mediators are involved. A mannitol test can be used to monitor response to steroids and is more sensitive than histamine for identifying persistent airway hyperresponsiveness in asthmatics well controlled on steroids. These findings suggest that indirect challenges give more useful clinical information about currently active asthma and the response to treatment than direct challenge and they will become more widely used.

Exercise in elite summer athletes: Challenges for diagnosis

BACKGROUND

There is a high prevalence of asthma and exercise-induced bronchoconstriction (EIB) in elite athletes when the diagnosis is based on symptoms and medication use. Objective measurements are now required by some sporting bodies to support a diagnosis of asthma or EIB to justify use of beta-agonists. Such measurements could include bronchial provocation with methacholine, with eucapnic voluntary hyperpnea (EVH) of dry air (a surrogate for exercise), or both.

OBJECTIVE

The aim of the study was to investigate the relationship between asthma symptoms and responses to methacholine and the EVH challenge in a group of unselected elite summer-sport athletes. The outcome would be to inform practitioners of a suitable objective approach to identifying those with asthma and EIB.

METHODS

Fifty elite summer-sport athletes with or without asthma were recruited from sporting teams and sports medicine centers throughout Melbourne, Australia. All subjects completed a respiratory questionnaire and, on separate days, underwent a bronchoprovocation challenge test with methacholine and EVH.

RESULTS

Forty-two subjects reported one or more respiratory symptoms in the past year, 9 had positive methacholine challenge results (mean PD(20) of 1.69 +/- 2.05 micromol), and 25 had positive EVH challenge results (mean fall in FEV(1) of 25.4% +/- 15%). Although all subjects with positive methacholine challenge results had positive EVH challenge results, methacholine had a negative predictive value of only 61% and a sensitivity of 36% for identifying those responsive to EVH.

CONCLUSION

These findings suggest that the pathogenesis of EIB in elite athletes might be different from that of asthma, and as such, neither symptoms nor the methacholine challenge test should be used exclusively for identifying EIB.

Outcome in adulthood of asymptomatic airway hyperresponsiveness in childhood: a longitudinal population study

The clinical outcome of asymptomatic airway hyperresponsiveness (AHR) first detected in childhood is sparsely reported, with conflicting results. We used a birth cohort of 1,037 children followed to age 26 years to assess the clinical outcome of asymptomatic AHR to methacholine first documented in study members at age 9 years. Of 547 study members who denied wheezing symptoms ever at age 9 years, 41 (7.5%) showed AHR. Forty showed methacholine responsiveness, with a provocation concentration of methacholine that elicited a 20% drop in forced expired volume in 1 sec (PC(20)) < or = 8 mg/mL, and one had baseline airway obstruction with a bronchodilator response exceeding 10%. Of these 41 study members, 18 (44%), 11 (27%), and 4 (10%) maintained AHR in 1, 2, and 3 later assessments, respectively, while 23 (56%) manifested AHR only at age 9. Compared with asymptomatic study members without AHR, those with asymptomatic AHR at age 9 years were more likely to report asthma and wheeze at any subsequent assessment, were more likely to have high IgE levels and eosinophils at ages 11 and 21, and more often demonstrated positive responses to skin allergen testing at ages 13 and 21 years. Persistent AHR at later assessments increased these likelihoods further.In conclusion, asymptomatic children with AHR are more likely to develop asthma and atopy later in life compared with asymptomatic children without AHR. Persistent AHR, even though initially asymptomatic, was associated with an even greater increased risk of development of asthma. We suggest that rather than considering AHR as a marker of asthma, it should be regarded as a parallel pathological process that may lead to subsequent symptoms and clinical evidence of asthma.

Issues in identifying asthma and estimating prevalence in an urban school population

This article first presents salient issues related to identifying children in urban schools who might benefit from asthma services. It discusses a brief questionnaire for identifying cases and problems in estimating asthma prevalence. Subsequently, results of case detection in 14 urban schools are presented and discussed in light of these issues. The questionnaire was employed with parents of 4,653 African-American children in Detroit. Results suggest that determining number, type, and frequency of symptoms may be necessary to ascertain prevalence of asthma. Using only number and type produced a rate of asthma of 25%. Adding frequency provided a more conservative estimate of 19%. About 9% of children exhibiting symptoms of asthma had no physician diagnosis. Only 25% with symptoms reflecting mild persistent, 35% with moderate persistent, and 26% with severe persistent disease had prescriptions for anti-inflammatory medicine. Further, 23% of children with asthma-like symptoms had no prescription for asthma medicine of any type.

CONCLUSIONS

(1) low-cost procedures can be used in schools to identify children with suspected undiagnosed and undertreated asthma; (2) prevalence estimates for asthma in the group of urban school children studied are among the highest in the United States; and (3) asthma is undertreated in this sample.

Predictors of methacholine responsiveness in a general population

OBJECTIVE

Methacholine responsiveness is an end point widely used in epidemiologic studies of asthma. This study aims to quantify the relative importance of different predictors of responsiveness such as age, sex, airway caliber, smoking and atopic status, and potential interactions deserving further investigation.

METHODS

Methacholine challenge was performed in 7,126 participants (aged 18 to 60 years) of the Swiss Study on Air Pollution and Lung Diseases in Adults according to the European Respiratory Health Survey protocol. Responsiveness was quantified by the slope between percentage decrements in FEV(1) and cumulative methacholine dose. Variation of slopes according to sex, smoking, and atopy was then examined separately by multivariate regression models that controlled for baseline FEV(1).

RESULTS

We found a nonlinear relationship between methacholine slope and baseline FEV(1) for both sexes, which could be well described by a quadratic function. The corresponding curves were almost identical in the region of overlap for male and female neversmokers. Methacholine responsiveness declined with age. The slope of this decline was less steep among nonatopic persons and nonsmokers compared with atopic neversmokers. Methacholine responsiveness increased with the number of cigarettes smoked per day and with the number of positive skin-prick test results (except among heavy smokers).

CONCLUSIONS

Our multiple regression results show that bronchial responsiveness (BR) varies with age, FEV(1), and smoking and atopic status. They suggest that there is a physiologic basis for the univariate sex difference in BR. Secondly, they show that while smaller airways are more responsive than larger ones, the reduction of responsiveness diminishes with each increase of lung size. The quantification of the relative influence of the different factors examined should help in the interpretation of BR.

Clinical and immunologic factors associated with the presence or absence of airways hyper-responsiveness in childhood asthma

BACKGROUND

During the baseline period of a clinical trial comparing different dosage schedules of inhaled steroids, asthmatic children (aged 6-10 years) were expected to meet the inclusion criterion of airways hyper-responsiveness (PD(20) methacholine < 80 micro g) after withdrawal of inhaled corticosteroids for 2-8 weeks. However, many children failed to do so.

OBJECTIVE

It has been shown that young wheezing children may outgrow their symptoms. We investigated if differences between children with and without airways hyper-responsiveness after withdrawal of inhaled corticosteroids were compatible with differences between transient and persistent wheezers found in other studies.

METHODS

Seventy-eight children entered the study, of which 41 developed airways hyper- responsiveness after withdrawal of inhaled corticosteroids, and 37 did not. These two groups of children were compared with respect to differences in demographic, clinical, and immunological features (IL-4, IL-5, IL-10, and IFN-gamma produced by Con A stimulated peripheral mononuclear cells (PBMCs) and serum IL-4, IL-5 and soluble intercellular adhesion molecule-1 (sICAM-1)).

RESULTS

Hyper-responsive children had more atopic features (positive RAST, high IgE, eczema), lower levels of FEV1 and lower concentrations of sICAM-1 than non-hyper-responsive children. Apart from a borderline significantly higher IL-4 production in the hyper-responsive group, other immunologic parameters were comparable. Multivariate logistic regression analysis showed that high serum IgE, low FEV1, and low sICAM-1 levels were independently associated with the presence of airways hyper-responsiveness after stopping inhaled corticosteroids. Atopy was associated with higher concentrations of IL-4 in the hyper-responsive group.

CONCLUSION

After withdrawal of inhaled corticosteroids many children previously diagnosed with asthma did not develop airways hyper-responsiveness. We conclude that hyper-responsive children share features with persistent wheezers as found in previous studies, whereas the non-hyper- responsive children may represent transient wheezers.

Risk factors for hospital admission for asthma from childhood to young adulthood: a longitudinal population study

BACKGROUND

Predictors of hospital admissions for asthma in children and young adults in a general population are not well defined, because most studies have used selected subpopulations.

OBJECTIVE

The purpose of this investigation was to determine risk factors for single and multiple hospital admissions for asthma.

METHODS

The members of a population-based, unselected birth cohort of 1037 New Zealanders answered questionnaires and underwent lung function, airway responsiveness, and allergy testing on 7 occasions to the age of 26 years.

RESULTS

Among the 766 study members (74% of the cohort) who reported wheezing symptoms ever by the age of 26 years, 136 hospitalizations were reported by 62 individuals (8.3% of those at risk, 6.2% of the total cohort). Only 55 of these 136 admissions involved children less than 9 years of age; admissions continued to occur between the ages of 9 and 18 years (40 admissions) and at >18 years (41 admissions). Those admitted were predominantly male, had earlier ages of onset of symptoms, were more atopic, and had more airway hyperresponsiveness to methacholine than those not admitted. Frequent symptoms and low lung function were evident among the 45 study members with single admissions and even more evident among the 17 study members with multiple (2-10) admissions.

CONCLUSIONS

A surprisingly large fraction of this unselected population experienced hospitalization for asthma during the 26-year follow-up, many being admitted in later childhood, adolescence, and early adulthood. Clinical characteristics and markers of severity, including frequent respiratory symptoms, airway hyperresponsiveness, atopy, and low lung function, identify those at high risk for hospitalization for asthma, particularly with respect to multiple admissions.

Does low birth weight help to explain the increased prevalence of asthma among African-Americans?

BACKGROUND

Racial disparities in asthma prevalence are not fully explained. Previous studies have reported an association between low birth weight (LBW) and asthma. African-Americans are at a heightened risk for both conditions.

OBJECTIVE

The objective of this analysis was to study a sample of suburban schoolchildren to determine if increased asthma prevalence in African-Americans could be explained by report of LBW.

METHODS

Logistic regression was used to analyze telephone survey and clinical data for a sample of 126 children, aged 6 to 8 years.

RESULTS

African-Americans reported asthma (12.5% vs 5.3%) and LBW (16.6% vs 3.9%) more frequently than non-African-Americans. After adjusting for LBW, the odds ratio for the association of African-American race to asthma was reduced from 2.6 to 1.8, whereas LBW remained independently associated with asthma, adjusted odds ratio = 5.1 (95% CI:1.4 to 18.9). The adjusted population risk for asthma due to LBW was 0.31.

CONCLUSIONS

High rates of LBW for African-Americans may contribute to racial disparities in asthma prevalence.

Determinants of bronchial responsiveness to methacholine at school age in twin pairs

The methacholine inhalation challenge test (MIC) was used to evaluate bronchial responsiveness in 67 children who were the products of multiple pregnancies when they were 7-15 years old. At birth, 30 (45%) infants had intrauterine growth retardation (IUGR; birth weight <2 SD below normal birth weight, or birth weight difference >1.3 SD between twin-pairs), and 59 (88%) were born before 37 weeks of gestation. None of the children had doctor-diagnosed asthma. The provocative dose of methacholine causing a 20% fall in Wright's peak expiratory flow (WPEF) (PD20) was below 1,000 microg in 10 (15%) children, and they were classified as MIC responders. There were no differences in perinatal or neonatal factors between MIC responders and nonresponders; in particular, MIC responses did not differ between IUGR infants, and children with appropriate growth for gestational age (AGA) at birth. There were seven discordant pairs in which one child was a MIC responder and the other was not; 5 responders were IUGR, and 2 were AGA children (ns). Respiratory tract infections after the neonatal period were equally common in IUGR and AGA children. However, these infections were associated with later bronchial hyperresponsiveness. Doctor-diagnosed respiratory infections, numbers of antibiotic courses, episodes of otitis media, and the need for adenoidectomy, tonsillectomy, and tympanostomy were more common in MIC responders than in nonresponders. We conclude that IUGR was not associated with subsequent bronchial hyperresponsiveness in twin pairs assessed by the MIC test. A significant relationship was seen between bronchial hyperresponsiveness and infections after the neonatal period.

Features and severity of occupational asthma upon diagnosis: an Italian multicentric case review

BACKGROUND

The severity of occupational asthma (OA) at the time of diagnosis is not known. In this study we aimed to evaluate some features of the disease at the time of diagnosis, particularly looking at severity and treatment before diagnosis.

METHODS

Medical records of subjects (n = 197) who had received a diagnosis of OA in six specialized centres of Northern and Central Italy in the period 1992-97 were reviewed. The severity of the disease at the time of diagnosis was determined on the basis of symptoms, peak expiratory flow (PEF, percentage predicted), forced expiratory volume in one second (FEV1, percentage predicted), and PEF variability, following the criteria of the National Institutes of Health and World Health Organizaton (NIH/WHO) guidelines on asthma. Medications used in the month before diagnosis were recorded.

RESULTS

The most common etiological agents were isocyanates (41.6%), flours (19.8%), woods (9.7%) and natural rubber latex (7.6%). The level of asthma severity (AS) was mild intermittent in 23.9% patients, mild persistent in 28.9%, moderate in 41.6%, and severe in 5.6%. Asthma severity was positively associated with current or previous smoking (P < 0.05), and was not related to atopy and current exposure. A relationship with bronchial reactivity to methacholine was shown in subjects at work. Treatment before diagnosis was consistent with the NIH/WHO guidelines in only 13.2% patients, whereas 75.6% were undertreated and 11.2% were overtreated.

CONCLUSIONS

In this study we found that the majority of patients had mild asthma at the time of diagnosis and that cigarette smoking was associated with a greater severity. Moreover, the majority of patients were undertreated before etiological diagnosis.

Asthma, smoking and chronic cough in rural and urban adult communities in The Gambia

BACKGROUND

Asthma is reported to be rare in traditional rural communities, but is thought to be increasing as lifestyles become more urbanized or 'western'.

OBJECTIVES

A community-based survey of non-communicable diseases was conducted from October 1996 to June 1997, and included comparison of the prevalence of asthma, smoking and chronic cough in rural and urban Gambia.

METHODS

A cluster sample survey was conducted in a random sample of rural and urban adults (> or = 15 years of age). Subjects were asked about respiratory symptoms using a locally adapted version based on the IULTD questionnaire. Spirometry (basal, methacholine provocation and reversibility with a bronchodilator) and skin prick tests were performed on a randomly selected subsample of all subjects and those who, when interviewed, said they wheezed or had been diagnosed as asthmatic by a doctor.

RESULTS

Out of 2166 participants in the urban population, 4.1% reported having had wheezing or whistling in the chest in the previous 12 months, 3.6% reported doctor-diagnosed asthma, and 0.6% chronic cough. In the rural population with 3223 participants these figures were 3.3%, 0.7% and 1.2%, respectively. Wheeze was more common in women, cough for 3 months of the year was more common in the age-groups 45+. Those who reported that they currently smoked accounted for 34% in urban and 42% in rural men. Figures were much lower for women (1.5% and 6.0%). Seven out of 574 randomly selected subjects (1.4%) exhibited bronchial hyper-responsiveness to methacholine challenge. Four of 133 (3.0%) people with self-reported wheeze and 3/69 (4.3%) participants with doctor-diagnosed asthma reacted positively on bronchial provocation with methacholine. There was a remarkably high prevalence of positive skin prick tests to aeroallergens: 38% in participants with a history of wheeze and 27% in those without.

CONCLUSION

The prevalence of wheeze (particularly in association with bronchial hyper-responsiveness) was low in both rural and urban Gambia. This is in contrast to the relatively high prevalence of positive skin prick tests to aeroallergens (in both wheezers and non-wheezers), questioning the mechanisms of interaction between allergy and asthma and the presence of protective factors against asthma in this West African population. The high smoking rates justify international concern about tobacco marketing in developing societies.

Predictors for the severity of bronchial hyperreactivity in childhood asthma

Bronchial hyperreactivity (BHR) is a common characteristic of asthma and is shown to be a risk factor in the development and outcome of asthma. In this study, we aimed to assess the risk factors at referral for the severity of BHR, which was determined at the end of a mean of 3 yr of follow-up in 98 children with asthma [mean (+/- SD) age, 11.0 (+/- 3.4) yr, male/female = 50/48]. We also evaluated the cross-sectional risk factors for the severity of BHR in the observed children. Information on risk factors at referral was collected from the computer records of the patients followed by an end-of-study visit. Lung function, skin-prick, and bronchial provocation tests were done and total serum IgE level was measured on this visit. The relationship between BHR and risk factors was investigated by multiple linear regression analysis. A lower level of FEV1 % at referral was found to be an important predictor of more severe BHR at the end of the follow-up. None of the other risk factors evaluated predicted the severity of current BHR. We concluded that decreased lung function at referral is associated with a more severe BHR determined at the end of a 3-yr follow-up in children with asthma.

Increasing prevalence of bronchial hyperresponsiveness in three selected areas in East Germany. Bitterfeld Study Group

The prevalence of asthma, bronchial hyperresponsiveness (BHR) and allergic rhinitis in children was lower in East Germany compared to West Germany. The reasons for this difference are still not understood. This study tested the hypothesis that prevalence of BHR increased in East German children after reunification. Two consecutive cross-sectional surveys of schoolchildren aged 8-14 yrs from three communities in East Germany were carried out in 1992-1993 and 1995-1996. A subsample of 530 and 790 children with complete lung function and cold air challenge data was analysed. The prevalence of BHR increased from 6.4%, in 1992-1993 to 11.6% in 1995-1996 (odds ratio (OR): 2.0, 95% confidence interval (CI): 1.3-3.0, adjusted for age, sex, season, community and parental education). No changes were found for asthma, allergic rhinitis or allergic sensitization. In contrast, physician diagnosed bronchitis, pneumonia and frequent colds decreased significantly. The observed increase in the prevalence of BHR was reduced (OR: 1.5, 95% CI: 0.95-2.3) after adjustment for several indoor factors. In conclusion, while the prevalence of nonallergic respiratory diseases seems to decrease, the prevalence of bronchial hyperresponsiveness might be a first indicator of the suspected increase of asthma prevalence in East Germany. The present results give indirect evidence, that less respiratory infections may be associated with higher bronchial hyperresponsiveness.

A review of cough in children

Cough is a very common symptom of respiratory disease and reason for parents to seek medical attention. The article presents broad clinical guidelines on the approach to childhood cough and discusses current controversies of the management of cough in children.

The feasibility of airways hyperresponsiveness as an inclusion criterion for studies on childhood asthma

The feasibility of moderately severe airway hyperresponsiveness (AH) was examined as an inclusion criterion for clinical trials in asthmatic children. During the baseline period of a long-term clinical trial in asthmatic children, maintenance therapy with fluticasone (200 microg x day(-1)) was stopped for a maximum of 8 weeks and methacholine challenges were performed at 2-week intervals or earlier if the patients' condition deteriorated. Patients were eligible to continue the study if the provocative dose of methacholine causing a 20% fall in forced expired volume in one second (FEV1) (PD20) was <80 microg. Fifty-one per cent of the children did not develop a PD20 < 80 microg after withdrawal of fluticasone. Patients with or without a PD20 <80 microg did not differ in duration of asthma, duration of treatment, or peak flow variation. Patients with a PD20 <80 microg had higher levels of total and specific immunoglobulin-E, and lower levels of FEV1 and mean maximal expiratory flow than patients with a PD20 > or = 80 microg. Forty-four per cent of the patients with a PD20 > or = 80 microg did not have any symptoms during the wash-out period and 39% of these patients remained free from symptoms during one year follow-up. The results of this study suggest that recruiting asthmatic children for clinical trials may be difficult if airways hyperresponsiveness is used as the sole inclusion criterion.

Validation of a new questionnaire on asthma, allergic rhinitis, and conjunctivitis in young adults

BACKGROUND

Epidemiologic data on asthma and allergies among adults are mainly based on questionnaires: this study validates the questions on asthma, allergic rhinitis, and conjunctivitis of a new Finnish questionnaire.

METHODS

To validate questions used in a country-wide study among university students aged 18-25 years, we examined 150 subjects who had ever reported asthma or wheezing, and 140 without asthma symptoms. Questions were validated in relation to current diseases including 1) symptoms detected during the preceding year at the physician's interview 2) objective measurements, such as methacholine challenge, skin prick tests, and specific IgE. Data were adjusted for original proportions of "asthmatics" and"nonasthmatics" in the questionnaire study.

RESULTS

Questions on "reported asthma" and "doctor-diagnosed asthma" had good positive predictive value (PPV) and specificity in diagnosing current asthma. The question on "attacks of shortness of breath with wheezing", and especially the question on "cough with wheezing" were most sensitive. Questions on "allergic nasal symptoms" and "allergic eye symptoms" that were "related to pollen or animals" were sensitive, but a further question on doctor's diagnosis yielded higher specificity and PPV.

CONCLUSION

Diagnosis-based questions were found suitable for risk-factor studies, because of their good specificity and PPV, and symptom-based questions for screening, because they were highest in sensitivity.

Asthma diagnosis and management in adults: is the risk of underdiagnosis and undertreatment related to patients' education levels?

To determine the relationship between patient education and the risk of underdiagnosis and undertreatment of asthma, a cross-sectional study of 500 (250 males and 250 females) adult attendees between 16 and 44 years of age was undertaken at five primary health care (PHC) centers in Al-Ain, United Arab Emirates. We used an Arabic translation of the European Community Respiratory Health Survey Screening Questionnaire. Asthmatics with higher levels of education had a significantly higher risk of underdiagnosis and undertreatment than asthmatics with less education. Doctors at PHC centers railed to diagnose 34.6% of the asthmatics with lower levels of education and 77.6% of the patients with higher levels of education. Eighty-five percent of the asthmatics with lower levels of education and 46.6% of the asthmatics with higher levels of education recognized that they had asthma. Thirty-eight percent of the asthmatics with lower levels of education and 83% of the asthmatics with higher levels of education were undertreated. It was found that 19% of the asthmatics with lower levels of education and 3% of the asthmatics with higher level of education were on prophylactic medication for asthma. We concluded that education level was related to underdiagnosis and undertreatment of asthma among adults between 16 and 44 years of age. People with higher levels of education have a higher risk of underdiagnosis and undertreatment than do those with lower levels of education. The factors that might be associated with these findings need to be explored in further studies.

Airflow limitation during respiratory syncytial virus lower respiratory tract infection predicts recurrent wheezing

BACKGROUND

Respiratory syncytial virus (RSV) lower respiratory tract infection (LRTI) is frequently followed by recurrent wheezing. Thus far no clinical risk factors have been identified to predict which infants will have wheezing episodes subsequent to RSV LRTI.

OBJECTIVE

To determine clinical predictors for airway morbidity after RSV LRTI.

METHODS

In a 1-year follow-up study we investigated the predictive value of auscultatory findings characteristic of airflow limitation (wheezing) during RSV LRTI for subsequent airway morbidity. Clinical characteristics, including the presence or absence of signs of airflow limitation, of hospitalized infants with RSV LRTI were prospectively recorded during 2 winter epidemics. During a 1-year follow-up period parents of 130 infants recorded daily airway symptoms.

OUTCOME MEASURE

Recurrent wheezing defined as > or = 2 episodes of wheezing.

RESULTS

Signs of airflow limitation during RSV LRTI were absent in 47 (36%) infants and present in 83 (64%) infants. Recurrent wheezing was recorded in 10 (21%) infants without signs of airflow limitation and in 51 (61%) with signs of airflow limitation during initial RSV LRTI (relative risk, 0.29, P < 0.001). In a multiple logistic regression model, airflow limitation during initial RSV LRTI proved independent from other clinical parameters, including age, parental history of asthma and smoke exposure.

CONCLUSIONS

A sign of airflow limitation during RSV LRTI is the first useful clinical predictor for subsequent recurrent wheezing.

Histamine challenges discriminate between symptomatic and asymptomatic children. MAS-Study Group. Multicentre Allergy Study

The aims of this study were to investigate a threshold value for bronchial responsiveness in children aged 7 yrs, which discriminates between symptomatic and asymptomatic children, and to identify determinants of this responsiveness. Titrated bronchial histamine challenges using the reservoir method were performed in 645 children aged 7 yrs, from the birth cohort Multicentre Allergy Study (MAS). When defining a reference population of healthy children within the MAS cohort, the 95th percentile of the provocative concentration causing a 20% fall in forced expired volume in one second PC20 among these asymptomatic study subjects amounted to 0.60 mg x mL(-1). This resulted in a specificity of 93.0% and a sensitivity of 45.9%, for discriminating between "current wheezers" and "non-current wheezers". Determinants of airway responsiveness at this age were pulmonary function, sensitization to indoor allergens, total immunoglobulin E and current wheeze. The results indicate that a very low cut-off provocative concentration causing a 20% fall in forced expired volume in one second (<1.0 mg x mL(-1)) defines airway hyperresponsiveness in children aged 7 yrs using the reservoir method. Provocation protocols for histamine challenges in this age group should therefore start with concentrations markedly below 1.0 mg x mL(-1).

Development of bronchial hyperresponsiveness during childhood

Bronchial hyperresponsiveness (BHR) produces the characteristic pathological abnormalities seen in asthma and clearly plays a central role in the pathophysiology of asthma. The presence of BHR has been demonstrated in infants with asthma, as has the possibility of BHR persisting through the childhood period. The level of BHR may not only reflect the state of the airways, as a marker of airway dysfunction, but may also predict the persistent prognosis of the disease. Thus, measurement of BHR may provide important information about the symptoms and lung function in children with asthma. In view of multiple pathophysiological mechanisms, BHR does not seem to have a single cause. Many potential confounding variables, such as age, gender and genetic status, and some environmental factors, such as allergens, infections, and pollutants, could be responsible for the establishment of childhood BHR. There may be differences between the mechanisms that induce transient BHR and the mechanisms that induce persistent BHR. Also, there may be differences between the causes that induce BHR in the infantile period and the causes that maintain persistent BHR during childhood asthma. There is also disagreement as to the most suitable method to measure BHR in children, especially in infants. The assessment of BHR in young children has not been uniformly successful, and measurements of BHR changes over the childhood period (are associated with a number of problems. To resolve these problems, there may be two ways to study childhood BHR. One is to use age-matched specific techniques to clarify the precise BHR in each age group; the other is to use simple techniques that can be performed over the childhood period on a large number of subjects. In studies of infantile respirator, dysfunction the ultimate goal is to establish a simple, noninvasive method by which measurements of respiratory function may be obtained in infants. Further investigations and acceptable methods will be needed to clarify, the mechanisms involved in the establishment of asthma throughout the childhood period.

Methacholine inhalation challenge: a shorter, cheaper and safe approach

Increased nonspecific bronchial hyperresponsiveness to pharmacological agents such as histamine or methacholine (MCh) is a hallmark of asthma. The measurement of airway reactivity is quite sensitive but testing is tedious, and time and money consuming. The present aim was, therefore, to design the shortest possible, yet safe inhalation challenge protocol applicable for a lung function referral centre. All records of studies performed in our institution during 1996 were analyzed retrospectively with a baseline ratio (bl) of forced expiratory volume in one second/forced vital capacity (FEV1/FVC) > or = 0.7 (n=449). It was questioned what the initial dose should be, and whether some inhalation steps could have been skipped without losing pertinent information and/or causing an adverse response (a fall in FEV1 >40%). When unavailable, provocative dose causing a 20% fall in FEV1 (PD20) values were obtained by linear inter- or extrapolation of the existing data. The present study showed that three-fold concentration steps could have been employed with minimal change in outcome. Only 151449 patients (3.3%) would have experienced a severe response. Five subjects (of 169, 3.0%) with FEV1/FVCbl 0.7-0.8 reacted to inhalation up to 0.073 micromol. Four subjects (of 280, 1.4%) with FEV1/ FVCbl> or =0.8 reacted to inhalation up to 0.219 micromol. The authors suggest that: 1) an initial dose of 0.219 micromol (initial concentration= 0.21 mg.mL(-1)) may be used when the baseline ratio of forced expiratory volume in one second to forced vital capacity > or =0.8 and 0.073 micromol (initial concentration=0.07 mg.mL(-1)) when the baseline ratio is <0.8; 2) a tripling dose protocol is easier to perform, cheaper and 30.2%, faster, yet just as safe; and 3) other abbreviated protocols used in epidemiologic settings may not be applicable in a referral centre setting.

Exercise-induced asthma: is it the right diagnosis in elite athletes?

Exercise-induced asthma, as recognized in asthmatic subjects, is an exaggerated airway response to airway dehydration in the presence of inflammatory cells and their mediators. The airway narrowing is primarily caused by contraction of bronchial smooth muscle. The milder airway narrowing documented in response to exercise in elite athletes and otherwise healthy subjects may simply be the result of the physiologic responses and pathologic changes in airway cells arising from dehydration injury. These changes, which include excessive mucus production and airway edema, would serve both to cause cough and to amplify the narrowing effects of normal bronchial smooth muscle contraction, resulting in symptoms. These changes are more likely to occur in healthy subjects who exercise intensely for long periods of time breathing cold air, dry air, or both. Under these conditions, the ability to humidify inspired air may be overwhelmed, causing significant dehydration of the airway mucosa and an increase in osmolarity, even in small airways. In addition to dehydration injury, airway narrowing to pharmacologic and physical agents may occur as a result of injury caused by large volumes of air containing irritant gases, particulate matter, or allergens being inspired during exercise. As a result, the airways may become inflamed, and the airway smooth muscle may become more sensitive. These events could result in the same exaggerated airway response to dehydration, as documented in asthmatic subjects.

Citrus red mite (Panonychus citri) is a common sensitizing allergen among children living around citrus orchards

BACKGROUND

A recent investigation has suggested that Panonychus citri (citrus red mite) is the most common causative allergen in citrus-cultivating farmers with asthma or allergic rhinitis.

OBJECTIVE

A cross-sectional survey was performed to evaluate the prevalence of asthma and sensitization to P. citri among children living around citrus orchards.

METHODS

A total of 1,055 children living around citrus orchards were enrolled. There were 544 boys and 511 girls with a mean age of 12.3 (range 7 to 16) years. They were evaluated by the ISAAC questionnaire, and a skin prick test with 13 common aeroallergens including P. citri and Japanese cedar pollen. Children who recorded ever having experienced wheezing on the questionnaire were evaluated by methacholine bronchial provocation test and determined to have asthma if they showed bronchial hyperresponsiveness to methacholine simultaneously.

RESULTS

The positive skin test response to one or more inhalant allergens except P. citri was 35.5%, but when including P. citri, the positive response increased to 37.7%. The most common sensitizing allergens in the order of decreasing frequency were Dermatophagoides pteronyssinus (26.6%), D. farinae (22.7%), P. citri (14.2%), cockroach (11.3%), and Japanese cedar pollen (9.7%). Among the children without sensitization to house dust mites, the sensitization rate to P. citri was significantly higher in those 13 and over than in those under 12 (5.8% versus 2.5%, P < .05). The prevalence of asthma was not different between the children with sensitization to P. citri and those without it (5.4% versus 4.0%, P > .05), although the prevalence was higher in those with sensitization to D. pteronyssinus or D. farinae than in those without sensitization to these allergens (7.9% versus 2.9%, P < .05; 9.7% versus 2.6%, P < .05).

CONCLUSION

Citrus red mite is a common sensitizing allergen among children living around citrus orchards. The features of sensitization and development of asthma are different between citrus red mite and house dust mites.

Bronchial responsiveness to methacholine is increased in citrus red mite (Panonychus citri)-sensitive children without asthmatic symptoms

BACKGROUND

A recent investigation has suggested that citrus red mite (Panonychus citri, CRM) is a common sensitizing allergen among children living around citrus farms.

OBJECTIVE

A cross-sectional survey was performed to evaluate the bronchial responsiveness to methacholine in CRM-sensitive children without asthmatic symptoms.

SUBJECTS AND METHODS

A total of 375 children living around citrus farms were enrolled in this study. There were 201 boys and 174 girls with a mean age of 12.5 (range 7-16) years. Each subject was evaluated by a questionnaire, a skin prick test with 13 common inhalant allergens including CRM, and a methacholine bronchial provocation test (MBPT).

RESULTS

Positive rate of MBPT (PC20-methacholine < 25 mg/mL) was higher in atopic rhinitic and atopic control children than in nonatopic rhinitic and nonatopic control subjects (41.3% and 33.3% vs 17.2% and 15.4%, respectively, both P < 0.05). Slope of dose-response curve (DRS, %/mg/mL) was higher in atopic rhinitic children than in nonatopic rhinitic, atopic control and nonatopic control subjects (14.3 +/- 0.87 vs 9.4 +/- 0.72, 10.0 +/- 1.37 and 9.2 +/- 1.51, P < 0.05, respectively). Both the positive rate of MBPT and the DRS were increased in children with positive skin response to CRM than in those without sensitization (48.2% vs 22.9%, P = 0.0001; 15.6 +/- 1.26 vs 10.2 +/- 0.65, P = 0.0001).

CONCLUSION

Bronchial responsiveness is increased in citrus red mite-sensitive children even if they have no asthmatic symptoms.

Urinary eosinophil protein X in children: the relationship to asthma and atopy and normal values

BACKGROUND

In epidemiologic studies, it may be difficult to identify children with bronchial asthma. Since this is the most common chronic respiratory disease in childhood, and its prevalence is still increasing, reliable methods for identification of asthmatic children are required. This study evaluates the use of urinary eosinophil protein X (U-EPX) in epidemiologic studies in identifying atopic and asthmatic children.

METHODS

U-EPX was measured in 877 Austrian schoolchildren. The skin prick test (SPT) was performed with eight common aeroallergens, and established questionnaires were used to assess respiratory symptoms.

RESULTS

Of our cohort, 2.8% reported physician-diagnosed asthma, 5.1% reported wheezing within the last 12 months, and 24.1% were found to be atopic. In children with physician-diagnosed asthma, as well as in atopic children (positive SPT), median U-EPX levels were significantly higher than in healthy subjects (142.8 and 89.6 vs 63.9 microg/mmol creatinine, P<0.0001 and P<0.0001, respectively). In addition, perennial sensitization to inhalant allergens resulted in higher U-EPX levels than did seasonal sensitization. The odds ratio for U-EPX levels over the 90th percentile was significantly elevated for asthma, for wheezing, for nocturnal cough, and for breathlessness at exercise, as well as for seasonal and perennial sensitization. Pulmonary function was negatively related to U-EPX levels.

CONCLUSIONS

Measurement of U-EPX, which can be obtained easily, may be helpful in diagnosing both asthma and atopy in children. However, there is a great overlap between controls and symptomatics, a fact which reduces the sensitivity of U-EPX in determination of the prevalence of asthma in epidemiologic studies.

Corticosteroid-sparing options in the treatment of childhood asthma

During the last 30 years, a significant rise in wheezing illness has occurred in the child population. Despite its high prevalence there is no clear definition of the disease, which includes a heterogeneous group of syndromes ranging from transient wheezing in infancy to atopic asthma with persistence into adult life. Molecular advances and further epidemiological information from well characterised individuals and their families are likely to clarify the different subtypes of wheezing illness and inform therapeutic options. With the recognition that chronic airway inflammation is a feature of persistent disease, at least in adults, there has been a trend towards the early introduction of anti-inflammatory treatment and particularly inhaled corticosteroids (ICS). However, the natural resolution of much wheezing illness, particularly in young children and in children with viral-induced episodes, suggests that newly presenting children should remain on symptomatic therapy alone while the severity of the disease is being assessed. Although ICS have become a cornerstone of management of chronic persistent disease, their ability to protect against exacerbations in young and mildly affected children is questionable. Alongside concerns about long term use of ICS and possible systemic adverse effects, there remains a need for alternative approaches to the control of the disease in children. Extrapolation of the findings of large multicentre adult studies into childhood, particularly for doubling the doses of ICS and long-acting beta2-agonists, may be unsound. Other approaches include the early introduction of inhaled cromones, use of second generation antihistamines, low dose theophyllines and, more recently, leukotriene modifiers. As the majority of preschool children will become asymptomatic by mid-childhood, there is an urgent need to identify those in whom chronic airway inflammation is developing, as it is in this group that early introduction of ICS may be of maximum benefit. In the remainder, other approaches, including use of corticosteroid-sparing longacting P2-agonists and leukotriene modifying drugs, may be more appropriate. Safe and effective oral preparations such as leukotriene modifying drugs are likely to establish a significant role in the management of symptoms in children of all ages and with all types of asthma and wheezing illness.

Childhood asthma: causes, epidemiological factors and complications

Asthma is common in children and its prevalence in this age group is increasing. While the reasons for this reported increase, and indeed the true magnitude of the increase, remain unclear, there can be no doubt that asthma is now a major health problem in children worldwide. Fortunately, our knowledge of the pathophysiology of asthma is also increasing. It is now known that asthma is a chronic inflammatory disease regulated by a variety of mediators, of which perhaps the leukotrienes are among the most important. This new understanding of the pathophysiology of the disease has spurred the development of the antileukotriene agents, which can be expected to play an increasingly important role in the management of childhood asthma.

Racial differences in physiologic parameters related to asthma among middle-class children

BACKGROUND

Asthma morbidity and mortality are higher in the United States for African-American (AA) children when compared to European-American (EA) children.

STUDY OBJECTIVES

To explore racial differences in physiologic factors associated with pediatric asthma severity.

DESIGN

Cross-sectional.

METHODS

We analyzed data from two groups of children in suburban Detroit, one of which contains non-urban, middle-class AA children, a group not usually included in childhood asthma studies. All children were 6 to 8 years of age. Clinical evaluations included medical history, physical examination, skin testing, spirometry, and methacholine challenge.

RESULTS

The study population (n = 569) was 14% African American, 51% of the participants were male, and the mean age was 6.8 +/- 0.4 years. Socioeconomic status (parental education) was similar overall by race, although some strata-specific differences were observed. The prevalence of physician-diagnosed asthma was 10% for both AA and EA groups. AA children were more reactive to methacholine than EA children (42% vs 22%, respectively; p = 0.001), and had significantly higher total IgE than EA children (geometric mean, 60. 6 vs 27.5 IU/mL; p = 0.001). Serum IgE was related to methacholine reactivity in EA children (p = 0.001), but not AA children (p = 0. 73). These differences remained after adjustment for gender, age, parental education, parental smoking, and maternal smoking during pregnancy.

CONCLUSIONS

Our data support previous reports of racial differences in lung volume, airway responsiveness, and serum IgE concentrations. We found a racial difference in the relationship between total serum IgE and airway responsiveness that is unreported elsewhere. Overall, our results suggest that AA children may be predisposed to asthma.

Factors related to methacholine airway responsiveness in children

Studies of airway responsiveness (AR) have typically used similar dose schedules of methacholine for adults and children despite large ranges in subject size. Reported declines in AR with increasing age in children could be due to maturational changes or to proportionately smaller doses of methacholine in taller (older) children. Other investigators have related both height and various measures of lung function to AR. We examined data related to AR in 471 children, aged 6 to 8 yr, from a birth cohort. Each child underwent spirometry followed by sequential challenge with five doses of methacholine, ranging from 0.025 to 25 mg/ml, given with a dosimeter. Continuous slope and end FEV(1)-change indexes of responsiveness were computed. Using stepwise regression modeling, we found no significant association between AR and either height or age after entering a variable reflecting asthma or wheezing. In contrast, we found that baseline measures of FVC, FEV(1)/FVC, and FEF(25-75%) were significantly related to AR after controlling for other variables (p = 0.001). However, when all three of the latter measures were added to models, FEF(25-75%) was most closely related to AR. We conclude that after control for other variables, FEF(25-75%) and FVC, but not height, are significantly related to methacholine responsiveness in children.

Inhaled mannitol identifies methacholine-responsive children with active asthma

Inhaled mannitol has been developed for bronchial challenge testing in adults. This study determined if mannitol could identify children with active asthma and responsive to methacholine, and whether mannitol challenge was faster to complete than methacholine challenge. Twenty-five children (aged 6-13 years) responsive to methacholine and 10 nonasthmatic children unresponsive to methacholine were studied. The methacholine challenge (Cockcroft protocol) was followed by a mannitol challenge on separate days. Twenty-one asthmatic children were positive to mannitol. Three taking inhaled corticosteroids with borderline methacholine responsiveness did not respond to mannitol, and one could not complete the mannitol challenge due to cough. The geometric mean (GM) and 95% confidence interval (CI) for PD(15) for mannitol was 39 mg (19, 78), and PC(20) for methacholine was 0.6 mg/mL (0.35-1.02) (r(p) = 0.75, p < 0.001, n = 21). Responses to mannitol were repeatable: GM PD(15) for the first challenge was 29 mg (CI: 17,50), and for the second challenge, 33 mg (CI: 20, 55) (P = 0.44, n = 9). Mannitol was faster to administer than methacholine (median (range)) 14 min (5-32) vs. 29 min (19-49), respectively (P < 0.001). Time to recover to baseline FEV(1) spontaneously and after bronchodilator administration was similar for both challenges. There were no significant falls in arterial oxygen saturations. During mannitol challenge, the mean (SD) fall in FEV(1) in nonasthmatic children was 3.1% (2.9). We conclude that mannitol identifies children with airway hyperresponsiveness and is faster to perform than the methacholine challenge.

Determinants of bronchial responsiveness at school age in prematurely born children

The bronchial challenge test using isocapnic hyperventilation of cold air (IHCA) was used to evaluate bronchial responsiveness in 63 offspring of multiple pregnancies when they were 8-15 years old. At birth, 27 (43%) children had had intrauterine growth retardation (IUGR, birth weight <-2 SD, or birth weight difference between twin pairs >1.3 SD). The median birth weight was 2,050 g (range, 800-3, 150), and the median gestational age was 35 weeks (range, 28-38). None of the children had asthma or suffered from asthma-like symptoms. In the interpretation of the IHCA test, a fall of 9% or more in the forced expiratory volume in 1 sec (FEV(1)) was considered as abnormal, and these children were classified as "cold air responders." The number of responders was 16 (25%); their baseline FEV(1)/forced vital capacity ratio (FEV(1)/FVC) and forced expiratory flow between 25-75% FVC (FEF(25-75)), but not FEV(1) were significantly lower than the corresponding values in nonresponders. No differences were found in perinatal or neonatal factors between responders or nonresponders. Eight (30%) of the 27 IUGR and 8 (22%) of the 36 appropriate for gestational age (AGA) children were IHCA responders. In particular, IUGR was not correlated with maximal FEV(1) falls following the IHCA test. Respiratory infections after the neonatal period were equally common in IUGR and AGA children; but infections were associated with subsequent IHCA responsiveness. Adenoidectomy, tonsillectomy, and/or myringotomy had been performed significantly more often in the responders than in the nonresponders. At least one of the above invasive procedures had been performed in 20 (32%) of the children; this group was termed the "ENT (ear, nose, throat) surgery group." Fifty-six percent of the responders, but only 26% of the nonresponders, belonged to the ENT surgery group (P = 0.02). We conclude that intrauterine growth retardation or prematurity is not associated with abnormal cold air responsiveness in the IHCA test.

Sensitivity to the house dust mite and airway hyperresponsiveness in a young adult population

BACKGROUND

The pathogenic mechanisms of airway hyperresponsiveness (AHR) in asthma are unknown and only a few studies have examined the importance of sensitivity to antigens in AHR in young adults.

OBJECTIVE

We investigated the correlation between AHR and sensitivity to specific antigens, atopy, history of childhood asthma and spirometry in a young adult population.

METHODS

Based on the results of interviews with 447 students at our university, 308 non-smoker students were classified into six groups. Group 1 comprised subjects with intermittent mild bronchial asthma; group 2, subjects with history of childhood asthma; group 3, subjects with atopic disease, and a RAST score for Dermatophagoides farinae (Def) of > or = 2; group 4, normal subjects with a RAST score for Def of > or = 2; group 5, subjects with cedar pollinosis; and group 6, normal subjects. We measured AHR to methacholine (MCh), spirometry, immunoglobulin E-radioimmunosorbent test (IgE-RIST), IgE-radioallergosorbent test to six common antigens, eosinophil cationic protein (ECP), and eosinophil count in peripheral blood in each subject.

RESULTS

Airway hyperresponsiveness to MCh did not correlate with IgE-RIST, eosinophil count, or ECP. The highest AHR to MCh was present in groups 1 and 2 and lowest in groups 5 and 6. Multiple regression analysis showed that sensitivity to Def was the only factor that significantly influenced AHR to MCh. Airway hyperresponsiveness to MCh of groups with a RAST score for Def of 0/1 was lower than groups with a RAST score of 2 to 6. Airway hyperresponsiveness to MCh did not correlate with the degree of positivity to Def antigen among positive sensitized groups (RAST score 2 to 6).

CONCLUSIONS

Sensitivity to mite antigen may be important in the pathogenesis of AHR and Def is a major contributing antigen in young adults in Japan. Once asthma occurs, AHR remains positive for a long time even after the disappearance of asthma-related symptoms.

Sensitivity and specificity of asthma definitions and symptoms used in a survey of childhood asthma

We compared the ability of definitions/symptoms of asthma to identify urban, elementary schoolchildren with physician-diagnosed asthma and bronchial hyperresponsiveness (BHR) post-exercise challenge. Definitions of asthma from the literature were compared, including American Thoracic Society (ATS) and British Medical Research Council (BMRC) definitions. Modified ATS had the highest sensitivity (77%), whereas BMRC had the highest specificity (99%). The most sensitive symptom was "wheeze with cold" (89%). The most specific symptoms were "medication required," and "breathing normal between attacks" (95%). Definitions and symptoms were poor predictors of BHR. Researchers can use these estimates in selecting and defining specific populations of children with asthma.

Citrus red mite (Panonychus citri) is the most common sensitizing allergen of asthma and rhinitis in citrus farmers

OBJECTIVE

To evaluate type I hypersensitivity to citrus red mite (Panonychus citri), its prevalence, and relationship to respiratory dysfunction, a cross-sectional survey was performed among citrus farmers on Cheju Island, Korea.

MATERIALS AND METHODS

Questionnaires, and skin prick test responses to 11 common inhalant allergens and citrus red mite were performed in 181 citrus farmers, and serum-specific IgE antibodies to citrus red mite were measured by ELISA in sera of 123 subjects. To determine airway hyperresponsiveness, methacholine bronchial provocation tests were performed in 55 subjects who complained of recurrent lower respiratory symptoms.

RESULTS

The prevalence of asthma-based on presence of asthmatic symptoms on the questionnaire and airway hyperresponsiveness to methacholine, and allergic rhinitis based on presence of nasal symptoms on the questionnaire and positive skin-test response were 12.1% and 19.3%, respectively. The positive rate of skin responses to one or more of 11 common inhalant allergens excluding citrus red mite was 17.1%, and if citrus red mite was included, 25.9% of farmers had positive responses. On skin prick tests, citrus red mite (16.5%) was the most common sensitizing allergen, followed by cockroach (11.0%), Dermatophagoides pteronyssinus (9.9%), and D. farinae (9.3%). Among farmers with asthma and allergic rhinitis, the positive skin responses to citrus red mite were noted in 54.5 and 68.5%, respectively. Serum-specific IgE antibodies to citrus red mite were detected in 45 farmers (36. 5%) of the 123 tested, and there was significant correlation between specific IgE level and weal (A/H ratio) to citrus red mite (r = 0.57, P < 0.001). The prevalence of asthma was higher in subjects with positive skin responses or high serum-specific IgE antibodies to citrus red mite than in those without skin response or serum specific IgE (P < 0.05, respectively).

CONCLUSION

Citrus red mite is the most important allergen in citrus farmers with asthma and rhinitis in which causative allergen has not been identified. It should be included in the skin test battery for screening the causative allergen in farmers exposed to citrus red mite.

Prevalence and burden of illness for asthma and related symptoms among kindergartners in Chicago public schools

BACKGROUND

Asthma mortality rates in poor communities of Chicago are among the highest in the country. Possible explanations include increased asthma prevalence, increased severity, and suboptimal health care.

OBJECTIVE

To estimate the prevalence of asthma and asthma-related symptoms among inner-city kindergarten children, and to characterize their burden of illness, asthma-related health care access, and pharmacologic treatment.

METHODS

Cross-sectional survey of parents of kindergartners was conducted in 11 randomly selected Chicago elementary schools. A self-administered 16-item questionnaire was given to parents of kindergartners. Parents who reported doctor-diagnosed asthma or at least one of several key asthma-related symptoms were then interviewed with a supplemental questionnaire examining asthma-related health care and medication use.

RESULTS

Based on data from 638 children [mean age 5.7 (SD = 0.6) years], the prevalence of diagnosed asthma was 10.8%. Sixteen percent of the respondents reported that their child had wheezed in the past year. The prevalence of asthma-related symptoms unassociated with a diagnosis of asthma was 30.1%. The children with diagnosed asthma had evidence of a high burden of illness: over 40% were reported to have had sleep disturbance due to wheezing > or =1 to 2 nights/week and 86.6% reported acute care visits for respiratory symptoms in the past year. Self-reported access to medical care was high. Over 40% of the children with doctor diagnosed asthma were reported to have used a beta2-agonist in the preceding 2 weeks, and 12.2% used an inhaled anti-inflammatory.

CONCLUSIONS

These data suggest that asthma prevalence in school-aged children in inner-city communities may be higher than US estimates. The burden of illness experienced by these children is substantial. Also, a large proportion of children were reported to have respiratory symptoms consistent with asthma, and no asthma diagnosis, suggesting possible undiagnosed asthma. While measures of health care access appear to indicate that the majority of children with asthma experience no identified barriers to health care, there is evidence to suggest undertreatment.

Cough, cough receptors, and asthma in children

This review discusses current general concepts on cough and the relationship between cough, cough receptor sensitivity, and asthma in children. It presents models of the relationship between cough and bronchoconstriction, and proposes a new model outlining the relationship between cough receptor sensitivity, airway hyperresponsiveness, and the clinical issues of cough, wheeze, and dyspnea in children with and without asthma. Cough is very common in children, with a prevalence of 15-20%. Those with non-specific cough (dry cough in the absence of identifiable respiratory illness) are often treated with a variety of drugs, in particular, medications for asthma and gastroesophageal reflux. However, there is little evidence to use these medications for the sole symptom of cough in children. Clinical studies on cough need to be interpreted in light of inherent methodological problems in studying cough. These methodological problems include the nonrepeatable nature of questions on cough, the unreliability of subjective measurements of cough, the lack of objective measurements to quantify cough severity, and the period effect (spontaneous resolution of cough). Although cough can be troublesome, cough serves as an important function for maintaining normal health of the respiratory system. The importance of cough in maintaining respiratory health is reflected in the development of lung atelactasis/collapse from retained secretions and recurrent pneumonia in clinical situations where the cough reflex is ineffective. The cough reflex is complex and still poorly understood. In this article the simplified cough pathway is presented and involves cough receptors, mediators of sensory nerves and the afferent pathway, the vagus nerve, the cough centre, efferent pathway, and cough effectors.

Exercise-induced bronchospasm in children: effects of asthma severity

The prevalence of exercise-induced bronchospasm (EIB) in asthmatic individuals has been reported to vary from 40% to 90%. There are, however, few studies addressing the effects of asthma severity on airway responsiveness to exercise. The purpose of the present study was to investigate the effects of asthma severity on EIB in children. We studied 164 children classified as having intermittent (n = 63), mild persistent (n = 30), moderate persistent (n = 40), and severe persistent asthma (n = 31) according to the Global Initiative for Asthma classification. Subjects exercised for 6 min on a cycle ergometer at 80% of their maximum heart rate, and spirometry was performed before and 5, 10, and 20 min after exercise challenge. The prevalence of EIB in children with moderate or severe persistent asthma was significantly greater than in children with intermittent asthma (p < 0.001). EIB-positive children with intermittent asthma exhibited smaller changes in FEV1 than children in the other three groups (p < 0.001). There was no significant relationship between baseline FEV1 and the decline in FEV1 after exercise. We conclude that the prevalence of EIB is greater in children with more severe asthma, and that the intensity of response to exercise is not consistently related to the clinical severity of asthma.

Mouse models of airway responsiveness: physiological basis of observed outcomes and analysis of selected examples using these outcome indicators

The mouse is an ideal species for investigation at the interface of lung biology and lung function. As detailed in this review, there are well-developed methods for the quantitative study of lung function in mice. These methods can be applied to mice in both terminal and nonterminal experiments. Terminal experimental approaches provide more detailed physiological information, but nonterminal measurements provide adequate data for certain experiments. In this review, we provide two examples of how these models can be used to further understanding of the primary pathobiology of airway responsiveness in both the absence and the presence of induced airway inflammation. The first model is a dissection of chromosomal loci linked to the variance in airway responsiveness observed in the absence of any manipulation to induce airway inflammation. The second model explores the role of T-cell costimulatory signals in the induction of airway hyperresponsiveness. As the number of mice with targeted deletions of effector genes or insertion of informative transgenes grows, additional examples are likely to accrue.

Respiratory symptoms and pulmonary function in an elderly nonsmoking population

OBJECTIVE

To examine risk factors for chronic airway disease (CAD) in elderly nonsmokers, as determined by pulmonary function tests (PFTs), and to correlate reported respiratory symptoms with PFT measures.

DESIGN

An observational survey.

SETTING

Several communities in California.

MEASUREMENTS

Exposures and respiratory history were assessed by standardized questionnaire. PFTs were performed and prediction equations derived.

RESULTS

Significant risk factors for obstruction on PFTs in multiple logistic regression included reported environmental tobacco smoke (ETS) exposure (relative risk [RR]=1.44), parental CAD or hay fever (RR=1.47), history of childhood respiratory illness (RR=2.15), increasing age, and male sex. The number of years of past smoking was of borderline significance (RR=1.29 for 10 years of smoking; p=0.06). The prevalence of obstruction on PFTs was 24.9% in those with definite symptomatic CAD, compared with 7.5% in those with no symptoms of CAD. The prevalence of obstruction was 36.0% among those with asthma and 70.6% among those with emphysema. Also, symptomatic CAD correlated with reduction in lung function by analysis of covariance. The mean percent predicted FEV1 adjusted for covariates was 90.6% in persons with definite symptoms of CAD, compared with 97.8% in those without it (p < 0.001).

CONCLUSIONS

Age, sex, parental history, childhood respiratory illness, and reported ETS exposures were significant risk factors for obstruction on PFTs. Self-reported respiratory symptoms also correlated significantly with PFTs.

Peak expiratory flow variability, bronchial responsiveness, and susceptibility to ambient air pollution in adults

Bronchial hyperresponsiveness (BHR) and peak expiratory flow (PEF) variability are associated expressions of airway lability, yet probably reflect different underlying pathophysiologic mechanisms. We investigated whether both measures can be used interchangeably to identify subjects who are susceptible to ambient air pollution. Data on BHR (>= 20% fall in FEV1), PEF variability (ampl%mean PEF > 5% on any day during an 8-d period with low air pollution levels) and diary data on upper and lower respiratory symptoms, cough, and phlegm were collected in 189 subjects (48-73 yr). The acute effects (lag0) of particulate matter with a diameter less than 10 micrometers (PM10), black smoke, SO2 and NO2 on the prevalence of symptoms were estimated with logistic regression. In subjects with airway lability, both when expressed as PEF variability (69%) and BHR (28%), the prevalence of symptoms increased significantly with increasing levels of air pollution, especially in those with the greater PEF variability (n = 55, 29%). We found no such consistent positive associations in adults without airway lability. PEF variability, and to a smaller extent BHR, can be used to identify adults who are susceptible to air pollution. Though odds ratios were rather low (ranging from 1.13 to 1.41), the impact on public health can be substantial because it applies to large populations.

Involvement of alpha-4 integrins in allergic airway responses and mast cell degranulation in vivo

Antibodies against integrins have been shown to inhibit allergic airway responses. The purpose of this study was to test the hypothesis that the beta1 integrin, very late antigen-4 (VLA-4), is involved in mast cell activation triggered by allergen exposure in sensitized animals. To do this we studied Brown Norway rats that were sensitized to ovalbumin (OA; 1 mg subcutaneously) using Bordetella pertussis as an adjuvant. Two weeks later rats were challenged with OA, pulmonary resistance (RL) was determined, and the concentrations of histamine and tryptase in bronchoalveolar lavage fluid and N-acetyl-leukotriene (LT)E4 in bile were measured. Pretreatment with a monoclonal antibody against VLA-4 (TA-2) attenuated the early response after OA challenge (342.9 +/- 24.4% baseline RL versus 153.3 +/- 19.4%; p < 0.01). There were significantly lower concentrations of histamine (67.11 +/- 11.90 microgram/ml versus 26.69 +/- 1.84; p < 0.01) and tryptase (0.143 +/- 0. 035 microgram/ml versus 0.053 +/- 0.022 microgram/ml; p < 0.01) in TA-2-treated animals. The increases in the concentrations of biliary N-acetyl-LTE4 after OA challenge were also significantly lower in TA-2-treated animals. These data suggest that a selective anti-VLA-4 monoclonal antibody prevents early responses through inhibition of mast cell activation.

A randomised, placebo controlled trial of inhaled salbutamol and beclomethasone for recurrent cough

AIMS

To test the hypothesis that inhaled salbutamol or beclomethasone will reduce the frequency of cough in children with recurrent cough. A secondary aim was to determine if the presence of airway hyperresponsiveness (AHR) can predict the response.

DESIGN

Randomised, double blind, placebo controlled trial.

METHODS

During a coughing phase, 43 children (age 6-17 years) with recurrent cough were randomised to receive inhaled salbutamol or placebo (phase I) for 5-7 days and then beclomethasone or placebo (phase II) for 4-5 weeks, and in a subgroup of children for 8-9 weeks. The children used an ambulatory cough meter, kept cough diaries, and performed the capsaicin cough sensitivity, hypertonic saline bronchoprovocation, and skin prick tests.

RESULTS

Salbutamol or beclomethasone had no effect on cough frequency or score, irrespective of the presence of AHR.

CONCLUSIONS

Most children with recurrent cough without other evidence of airway obstruction, do not have asthma and neither inhaled salbutamol nor beclomethasone is beneficial.

The impact of asthma and asthma-like illness in Seattle school children

The impact of asthma and asthma-like illness was measured in a population of 5-9-year-old Seattle public school children. Child health information was obtained from a survey of 1665 parents of first and second grade students to assess medical services use and impaired physical functioning among diagnosed asthmatics and those with current wheezing, defined as wheezing in the past 12 months without a diagnosis of asthma, relative to an asymptomatic population with neither condition. Relative to the asymptomatic population, the prevalence of respiratory-related activity limitation, and perception of poorer child health was larger among diagnosed asthmatics than children with current wheezing. However, the prevalence of sleep disturbances, school absences, medical services use, and parental concern over their child's health was similar for both the asthmatic and wheezing groups relative to the asymptomatic group. Also, in both symptomatic groups, a history of moderate or severe wheezing was associated with an increased prevalence of respiratory-related sleep disturbances and activity limitation. The similarity between the impact of diagnosed asthma and undiagnosed asthma-like illness suggests that the overall social and economic burden of asthma may be higher than previously estimated.