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

Epidemiological association of airway inflammation with asthma symptoms and airway hyperresponsiveness in childhood

The role of airway inflammation in childhood asthma is not well defined, despite modern treatment approaches recommending potent anti-inflammatory therapy for an increasing number of children. In this study, induced sputum analysis was used to investigate the relationships among sputum inflammatory cells (eosinophils and mast cells), asthma symptoms, and airway hyperresponsiveness to hypertonic saline in a cohort of 170 children aged 8-14 years. Children who reported asthma symptoms in the past 2 wk had a 2. 25-fold (95% to CI, 1.20-4.24) increased odds of having significant sputum eosinophilia. Hyperresponsiveness to hypertonic saline was strongly associated with higher levels of sputum eosinophils ([OR] 4. 36, 1.70-11.20), sputum mast cells (OR 7.46, 2.48-22.75), and nasal eosinophils (OR 4.73, 1.89-11.86). Interestingly, boys were more likely than girls to have features of airway inflammation (sputum mast cells, OR 3.33, 1.15-9.65; nasal eosinophils, OR 3.25, 1.72-5. 97), which is consistent with the known increase in asthma prevalence in boys in this age group. Airway inflammation with eosinophils and mast cells is likely to be important in the pathogenesis of asthma in childhood. Induced sputum analysis can be used to evaluate this problem and has the potential to be a useful tool for monitoring therapy.

Response-dose ratio as an index of bronchial responsiveness to hypertonic saline challenge in an epidemiological survey of asthma in Polish children

This epidemiological survey was done to evaluate the bronchial responsiveness (BHR) to a 4.5% hypertonic saline (HS) challenge in 13-14 year-old schoolchildren. BHR was measured by the response-dose ratio in which the response was estimated by the decline of FEV1 index of BHR (IxFEV1). Validity of the HS challenge test as a screening test for confirmation of reported asthma symptoms and the diagnosis of asthma was assessed. With a cutoff of 90th percentile of IxFEV1 in controls, the test sensitivity and specificity for asthma symptoms in the last 12 months was 44% and 90%, respectively. For the diagnosis of asthma the test sensitivity was 67% and specificity 90%. The mean log transform of IxFEV1 was significantly higher in children with more than three episodes of wheezing in the last 12 months and a diagnosis of asthma than in controls. Moreover, in the group with more than three episodes of asthma in the last 12 months the mean IxFEV1 was higher in girls than in boys. There was no gender difference in other groups of asthmatic children and controls. In Polish schoolchildren the prevalence of BHR to HS was 12.5% when adjusted to the prevalence of wheezing in the last 12 months. By multiple linear regression analysis, factors associated with BHR were serum levels of total IgE in children and of maternal IgE, as well as children's peripheral blood eosinophil counts. Also, the size of skin reaction to mite and dog allergens correlated with BHR.

Longitudinal determinants of bronchial responsiveness to inhaled histamine

BACKGROUND AND STUDY OBJECTIVE

The point prevalence of bronchial hyperresponsiveness (BHR) is imperfectly associated with current asthma, possibly due to changes over time in bronchial responsiveness (BR). To evaluate cross-sectional and longitudinal determinants of BR, a population sample comprising 408 children and adolescents, aged 7 to 17 years at enrollment, was examined twice, 6 years apart.

METHODS

Case history was obtained by interview and questionnaire. BR to inhaled histamine, pulmonary function, and skin prick test reactivity were measured using standard techniques.

RESULTS

The point prevalence of BHR (the concentration of histamine causing a 20% decline in FEV1 <8 mg/mL) declined from childhood to early adulthood (25% and 6%, respectively; p<0.001); and similarly a decline in histamine dose-response slope was observed. At both surveys, prechallenge FEV1 percent predicted, asthma, and atopy, especially atopy to house dust mite (HDM), were important determinants for the degree of BR. After adjustment for prechallenge FEV1 percent predicted, no male-female difference was observed in degree of BR. Lower FEV1 percent predicted (p=0.003), asthma (p<0.001), higher degree of BR (p=0.003), and atopy to HDM (p=0.007) at enrollment predicted a higher degree of BR at the second survey (degree of BR at second survey adjusted for prechallenge FEV1). Furthermore, new asthma (p<0.001) and/or atopy to HDM (p=0.003) were associated with higher BR at the second survey. Confining the analysis to nonasthmatics showed that subjects with new or persistent atopy to HDM had significantly increased BR compared with nonatopic subjects; and, moreover, prechallenge FEV1 percent predicted was significantly correlated with BR.

CONCLUSIONS

BR declines from childhood to early adulthood, possibly reflecting the increase in airway caliber. The level of FEV1 and atopy, especially to HDM, are important determinants for changes over time in level of BR, also in nonasthmatic subjects.

Malignant cough equivalent asthma: definition and case reports

BACKGROUND

Cough equivalent asthma is a cause for chronic cough and usually responds to corticosteroid therapy. Oral corticosteroids are employed in a diagnostic-therapeutic trial and inhaled corticosteroids are employed in maintenance therapy. In certain cases the cough may be especially severe and require escalated doses of oral corticosteroids for initial control. This is labeled malignant cough equivalent asthma.

OBJECTIVE

To define malignant cough equivalent asthma, provide two case reports, and identify features that should alert physicians to consider the possibility of malignant cough equivalent asthma.

CASE REPORTS

We report two patients who presented complaining of chronic cough that was disruptive of sleep and normal activities, and in one patient prompted an emergency room visit and later hospitalization. The patients underwent evaluation with history, physical examination, and laboratory testing as indicated. Other causes for chronic cough were ruled out by appropriate testing, or were treated, and patients did not respond to usual corticosteroid treatment for cough equivalent asthma. These patients were considered to have a more severe form of cough equivalent asthma and did respond to treatment with higher doses of oral corticosteroids.

CONCLUSION

Malignant cough equivalent asthma is a cause of chronic cough that is disruptive to sleep or normal activities, may lead to emergency room visits or hospitalization, and requires escalated doses of oral corticosteroids for initial control.

Prevalence of bronchial hyper-responsiveness in the southern, central and northern parts of Sweden

Studies have suggested that there is a higher prevalence of asthma in northern Sweden than in southern Sweden. Bronchial hyper-responsiveness (BHR) has been shown to be associated with asthma. The aim of this study was to explore the prevalence of bronchical hyper-responsiveness in different parts of Sweden. As part of the European Community Respiratory Health Survey (ECRHS), interviews, skin prick tests, lung function tests and methacholine provocation tests of the airways were performed in 1448 randomly selected subjects in southern, central and northern Sweden. The Mefar dosimeter was used according to the ECRHS protocol. The responsiveness was calculated both as the PD20 and as the dose response slope (DRS). BHR was defined as a PD20 of < or = 1.6 mg. Atopy was defined as at least one skin prick test of > or = 3 mm. The prevalence of BHR was 12.7%, 10.6% in men and 15.0% in women. No difference in prevalence was found between the three different regions of Sweden. The prevalence of BHR was higher in women than in men and higher in smokers than in non-smokers. Using multiple logistic regression, with BHR as the dependent variable, atopy, being female, having a low FEV1 (% predicted) and smoking (both own and passive) increased the odds of having BHR, while age and the region of Sweden did not influence BHR. Defining BHR as a PD20 of < or = 1.0 mg or a PD20 of < or = 2.0 mg did not change this. Multiple regression using log DRS as the dependent variable produced the same result. Both BHR and increasing DRS were associated with self-reported wheezing, attacks of shortness of breath during the daytime at rest or after strenuous activity, being awakened by a feeling of tightness in the chest or an attack of shortness of breath. In subjects without self-reported asthma, BHR was associated with self-reported wheezing and attacks of shortness of breath after strenuous activity. In conclusion, we found that the prevalence of BHR in the three investigated areas was 12.7%. We found a trend towards a higher prevalence of BHR in the most northerly of the study areas, but the difference between the areas was not statistically significant. BHR and DRS were associated with atopy, smoking, female sex and FEV1 (% predicted). The reporting of symptoms from the airways was associated with the degree of bronchical responsiveness.

Determinants of eosinophil cationic protein in nasal lavages in children

BACKGROUND

Nasal lavages are increasingly used to assess airways inflammation in children. However, there are no studies assessing how measurement error as well as biological influences contribute to the concentration of nasal inflammatory parameters in a population based survey.

OBJECTIVE

To investigate determinants of concentration of eosinophil cationic protein (ECP) in nasal lavages we studied 147 schoolchildren (mean age 8.1 years, SD 0.6 years) by repeated nasal lavages/year over a 2 year period.

METHODS

Standardized questionnaires were completed by the parents each year. A skin-prick test with seven aeroallergens (birch, cat, dog, hazel, weeds, Dermatophagoides pteronyssinus and D. farinae) was performed. One hundred and one children could perform valid lavages at least five times a year. As a measure of reproducibility the intraclass coefficient of reliability was calculated.

RESULTS

The intraclass coefficient of reliability was 0.27 over all observations suggesting that about a quarter of total variance is due to between-subject variance. Taking means over each year increased reliability to 0.60. Linear regression analyses with ECP being the dependent variable demonstrated significant higher values for boys (beta=12.26; P < 0.01), children sensitized to seasonal (beta=34.27; P=0.02) but not to perennial allergens (beta=-4.44; P=0.57), and for children with a serous (beta=10.01; P=0.01) or purulent rhinitis (beta=22.45; P < 0.001).

CONCLUSION

Assessment of inflammatory mediators in nasal lavages is a useful tool for epidemiological paediatric studies. However, due to the relatively high intraindividual variability of ECP concentrations multiple lavages are necessary to characterize the individual.

Defining the asthma phenotype for the purpose of genetic analysis

In 1991, we began a project to search for the genetic basis of asthma using linkage analysis. We encountered discord between a history of asthma and physiological measures of variable airflow obstruction and sought to examine the frequency of such occurrences and the issues surrounding phenotyping of patients with asthma. We reviewed our experience in ascertaining the asthma phenotype in 50 nuclear families comprised of 219 subjects (110 male, 109 female). Three respiratory physicians reviewed data including a questionnaire, skin testing, objective measures of variable airflow obstruction [increase in FEV1 > or = 15% following salbutamol 400 micrograms of PC20 (methacholine) < or = 4 mg/ml], and serum for IgE. Thirty-eight percent of subjects had both objective and questionnaire data consistent with asthma (++) whereas 39% had negative objective and negative questionnaire findings (--) (i.e., no asthma). A positive history but negative objective findings occurred in 7% of subjects, 2% had a negative history and positive objective findings. Retesting was requested in 13% of subjects; review of historical data was requested in 1% (i.e., childhood asthma but no present asthma). Retesting was requested for either (a) positive history, negative objective if symptoms were seasonal or the subject was using medications known to affect the challenge study, (b) viral infection within 6 weeks of a positive methacholine study, or (c) technically inadequate study. Overall, after the initial assessment, all members of only 22 families could be catagorized as either ++ or --. The diagnostic group requested at least 1 retest in 19 families and a review of historical records in 2 families. We conclude that discordance between self-reported questionnaire data and laboratory measures of variable airflow limitation is common and will increase the numbers of asthmatic subjects in studies that seek to determine the genetic basis of asthma.

Monitoring of bronchial asthma

Assessment of asthma severity is important for disease management. Analysis of symptoms past and present, and previous and actual lung function measurements (including variability) is the usual method of evaluation and classification of asthma disease severity and activity. However, symptoms and lung function alterations are the result of pathophysiological processes including inflammation in the bronchial wall which, in chronic phases, precedes the clinical measurements, and are risk factors for disease progression and worsening. Tools for more precise determination of asthma disease processes in the airway wall would be of importance for prophylactic intervention to avoid chronic damage to the airways and acute worsenings to occur.

Peak flow variability, methacholine responsiveness and atopy as markers for detecting different wheezing phenotypes in childhood

BACKGROUND

There is increasing evidence that wheezing during childhood may be a heterogeneous condition, and that different forms of wheezing may be associated with different risk factors and prognosis. The aim of this study was to determine if measures of airway lability and of atopy could identify distinct wheezing phenotypes during childhood.

METHOD

In a cohort of children followed from birth peak flow variability (n = 600) was evaluated and methacholine challenge responsiveness (n = 397) was measured at age 11 in relation to wheezing before the age of three, and at age six and 11 years total serum IgE and skin test reactivity to allergens were determined.

RESULTS

Neither positive peak flow variability nor methacholine hyperresponsiveness measured at age 11 were associated with wheezing occurring only during the first three years of life. Both methacholine hyperresponsiveness and positive peak flow variability were associated with wheezing at both ages six and 11 (OR 5.1 (95% CI 2.4 to 10.6) and 2.3 (1.2 to 4.5), respectively). In addition, positive peak flow variability was associated with wheezing up to the age of six but not at age 11 in non-atopic children (OR 2.9 (95% CI 1.0 to 8.8)). Methacholine hyperresponsiveness measured at age 11 was more frequently observed in boys (OR 2.1 (95% CI 1.2 to 3.5)) and was strongly associated with serum IgE levels measured at ages six and 11 (p < 0.001) and with positive skin test reactivity (OR 4.5 (95% CI 2.0 to 10.1)). Peak flow variability was unrelated to sex or markers of atopy (IgE and skin test reactivity).

CONCLUSIONS

Methacholine responsiveness and peak flow variability assessed at age 11, together with markers of atopy (IgE and skin test reactivity to allergens) identify three different wheezing phenotypes in childhood: "transient early wheezing" limited to the first three years of life and unrelated to increased airway lability; "non-atopic wheezing" of the toddler and early school years associated with positive peak flow variability but not with methacholine hyperresponsiveness; and "IgE-associated wheeze/asthma" associated with persistent wheezing at any age and with methacholine hyperresponsiveness, peak flow variability, and markers of atopy.

Genetics of native airway responsiveness in mice

The inbred mouse represents a powerful tool for dissecting both simple and complex traits. Genetic studies in the mouse should identify disease genes acting in the same biochemical pathway as in the human. Problems associated with genetic heterogeneity, inability to control environmental conditions, lack of an abundant supply of genetic markers, and ethical considerations regarding human genetic crosses are but some of the reasons to study airway responsiveness in the mouse. At present, only a handful of studies have shed light on the genetics of airway responsiveness; even fewer have sought to identify genetic loci that regulate this trait. It is clear that both genetic and environmental factors influence the asthma phenotype and that genetic background is an important consideration when interpreting segregation analysis data. The controversy over the specific mode of inheritance and number and location of quantitative trait loci (QTL) illustrates the need for additional studies. However, given that numerous candidate loci implicated in the pathogenesis of asthma map near QTLs identified in two recent studies, and given the considerable homology between the human and mouse genome, a targeted search for susceptibility genes is warranted in the human. Ideally, these regions will demonstrate linkage in humans. Thus, further work remains to be done to create detailed maps of the regions of linkage in the mouse, and to ultimately identify gene(s) that modify airway responsiveness. mice.

The diagnostic value of cold air hyperventilation in adults with suspected asthma

The diagnostic value of isocapnic hyperventilation of cold air (IHCA) is not fully established. All 342 adult patients in whom IHCA had been performed because of a clinical suspicion of asthma between 1992 and 1994 were analysed retrospectively in the authors' hospital. In addition, 26 healthy subjects were recruited. According to strict criteria, the patients were divided into asthmatics and symptomatic non-asthmatics. For the calculations of sensitivity, specificity and accuracy, the symptomatic non-asthmatic group served as a control. The post-test probability of asthma after IHCA was determined for all the possible pre-test probabilities by applying Bayes' theorem. A linear regression model was used to investigate the factors associated with the reactivity to IHCA. A single 4-min IHCA and skin prick tests were performed in the healthy subjects. Of the 287 patients in the final analysis, 113 were defined as asthmatics and 174 as symptomatic non-asthmatics. The accuracy was highest using a 9.0% fall in forced expiratory volume in 1 s (FEV1) as a cut-off value; the specificity was then 86.8% and the sensitivity 31.9%. The authors found IHCA to be a useful diagnostic test only if the pre-test probability of asthma is between 0.30 and 0.56. The positive final diagnostic gain of IHCA is 22% at its best, but the negative gain is negligible for all possible pre-test probabilities. Factors associated with reactivity to IHCA were young age and, to a lesser extent, a history of cold-weather-associated respiratory symptoms and pre-challenge bronchial obstruction. If a rigid cut-off value for a positive response is used in all age groups, the specificity of IHCA is good but the sensitivity is unacceptably low in adults. The diagnostic value of IHCA might increase if age is taken into account when defining the cut-off value.

Prevalence of childhood asthma based on questionnaires and methacholine bronchial provocation test in Korea

BACKGROUND

In most epidemiological survey studies, only subjective symptoms and past medical history of asthma have been used as diagnostic criteria. Even though a questionnaire survey can be performed in a large population study at low cost, limitations such as lack of objectivity and poor predictability in non-specific bronchial hyperresponsiveness cannot be avoided.

OBJECTIVES

The purpose of this study was to elucidate the prevalence of current asthma based on questionnaires and methacholine bronchial provocation test, and the prevalence of atopy in Korea.

METHODS

We performed modified ATS respiratory questionnaires and allergen skin-prick test with 10 common inhalant allergens among 3219 subjects aged 7-19 years in Seoul and a rural part of a small city, Chungju in Korea. Methacholine bronchial provocation tests were also performed among those who had asthma symptoms according to the questionnaire. The criteria of asthma was presence of both asthma symptoms and non-specific bronchial hyperresponsiveness. Atopy was defined as when an allergen induced weal size is same or larger than that caused by histamine.

RESULTS

The prevalence of asthma based on questionnaires and methacholine bronchial provocation tests was 4.6%, while the prevalence of wheeze was 8.2% and 19.3% of total population complained of one or more respiratory symptoms related to asthma on the questionnaires. There was no significant difference according to age, sex and living area. The mean prevalence of atopy was 35.0% and the most common allergens were Dermatophagoides farinae (30.9%), Dermatophagoides pteronyssinus (27.5%), cat fur (20.4%) and cockroach (11.8%). The atopy prevalence in Chungju area was higher than that in Seoul and males showed a higher prevalence than females. The asthma prevalence was higher among atopics (6.8%) than among non-atopics (2.7%). None of questionnaire items were enough to predict the presence of bronchial hyperresponsiveness in terms of sensitivity, specificity and positive predictive value.

CONCLUSION

The prevalence rate of current asthma in Korea was 4.6% and the prevalence rate of atopy in Korea was 35.0%. Questionnaire-based surveys are not enough to predict the actual prevalence of asthma.

Airborne (1-->3)-beta-D-glucan and airway disease in a day-care center before and after renovation

Changes in symptoms and airway responsiveness among persons who worked in a day-care center that had microbial growth problems were assessed before and after renovation. Before and after the building renovation, the investigators used the Limulus assay with (1-->3)-beta-D-glucan-specific lysate to measure airborne levels of (1-->3)-beta-D-glucan, a cell-wall component of molds. Airway responsiveness and subjective symptoms were measured among 14 female employees with a methacholine test and a standardized questionnaire. After the renovation, (1-->3)-beta-D-glucan-glucan levels decreased from 11.4 to 1.4 ng/m3. The number of persons who had increased airway responsiveness decreased after the renovation. Two employees developed a classical allergy to cat and pollen during the observation period. Although the study included only a few subjects and was based on only one day-care center, the data suggest that (1-->3)-beta-D-glucan may be related to airways inflammation caused by indoor air pollution.

Differential inhibitory effect of regular inhaled corticosteroid on airway responsiveness to adenosine 5' monophosphate, methacholine, and bradykinin in symptomatic children with recurrent wheeze

Indirect tests of bronchial responsiveness to agents such as adenosine 5'-monophosphate (AMP) or bradykinin might be more specific markers of a therapeutic responses to anti-inflammatory treatment than a test of direct responsiveness to agents such as methacholine. In children selected from the community on the basis of mildly symptomatic wheeze, we compared in a randomized, double-blind study design the effect of 400 micrograms/day of beclomethasone dipropionate (BDP) or placebo on three separate ways of provoking bronchial responsiveness, using methacholine, bradykinin, and AMP as the provoking agents. Following pretreatment bronchial challenges, 29 children received paired monthly methacholine and AMP challenges for 3 months, while for the same period another 33 children received paired monthly methacholine and bradykinin challenges. Compared with placebo-treated subjects, FEV1 increased significantly in the children receiving BDP. This improvement was observed in those randomized to either the AMP challenge or the bradykinin challenge. In children challenged with AMP, the PD20 AMP increased significantly after 1 month and 2 months of BDP therapy when compared with placebo, while under similar conditions the PD20 methacholine was not significantly affected. In children challenged with bradykinin, BDP therapy did not significantly alter either the PD20 bradykinin or PD20 methacholine. We conclude that a bronchial challenge with AMP appears to be a more sensitive predictor of response to anti-inflammatory treatment than either methacholine or bradykinin.

Testing airway responsiveness using inhaled methacholine or histamine

Airway responsiveness assessed using histamine and methacholine is safe, reproducible and relatively easily undertaken in adults and children. Results are similar for methacholine and histamine although methacholine is better tolerated. Responsiveness is increased in children and the elderly, and in women compared to men, possibly due to body size effects. Baseline lung function confounds the interpretation of airway responsiveness and may explain the effect of smoking in most studies. Results are most usefully expressed as the provocative dose producing a 20% fall in FEV1 (PD20FEV1) or the dose-response slope (DRS). When technical factors are controlled the reproducibility of the test is from one to two doubling doses. Measurements of airway responsiveness have been widely used in clinical and research practice. However, assessing their value in diagnosing asthma is limited by the lack of a gold standard for the definition of asthma. Using a cut-off value of 8 mg/mL or 8 mumol for PD20, the tests will discriminate asthmatic from non-asthmatic subjects (based on questionnaire definitions of asthma) with a sensitivity of around 60% and a specificity of around 90%. These properties of the test result in positive and negative predictive values of 86% and 69% when the prevalence of asthma is high (50%-as in the clinical setting) and 40% and 95% when the prevalence of asthma is low (10%, as in general population studies). In the usual clinical setting, assessing the significance of atypical or non-specific symptoms, the tests are of intermediate value in predicting the presence of asthma and less useful in excluding asthma. The additional benefit of testing airway responsiveness to measuring peak flows or to a trial of therapy has yet to be fully assessed. Testing of airway responsiveness may be of value in assessing occupational asthma, asthma severity and the effects of potential sensitizers or treatments. In research, tests of airway responsiveness are more useful for excluding cases of asthma. In population studies, they serve as an objective marker of abnormal airway function which may be genetically determined and, like allergy, are strongly associated with asthma. The predictive value of airway hyperresponsiveness for the development of airway disease is yet to be clearly established. In epidemiology the benefits of measuring airway responses must be weighed against the added inconvenience and cost that is incurred.

Assessment of asthma using automated and full-text medical records

Automated medical records systems are used to study clinical outcomes and quality of care, but this requires accurate disease identification and assessment of severity. We sought to determine the reliability of identifying asthmatics through automated medical and pharmacy records, and the adequacy of such data for severity assessment. All adult health maintenance organization (HMO) members who received at least one asthma drug and an asthma diagnosis between April 1988 and September 1991 were identified. Records of a random sample were reviewed to validate the diagnosis and extract clinical information. Asthma drugs were dispensed to 15,491 individuals; 7583 (49%) also received an asthma diagnosis. Asthma drug use was three times greater for persons with diagnosed asthma compared to those with no diagnosis. Record review revealed that a coded asthma diagnosis had a positive predictive value of 86%. Nearly 4000 ambulatory encounters were reviewed, 10% of which were for asthma; the median number of encounters was two. Asthma symptoms were mentioned in 9% of all encounters; wheezing was most common. Peak flow and spirometry were measured in 4% and 1% of encounters, respectively. Records from recipients of asthma drugs who lacked an asthma diagnosis showed that 79% did not have asthma. Automated medical and pharmacy records from an HMO were relatively accurate when used to identify individuals with asthma. Similarly, most asthma drug recipients who lacked a coded diagnosis of asthma did not have asthma. However, conventional full-text records usually do not contain sufficient information to assess asthma severity, limiting the utility of such records for research and quality improvement.

Targeted expression of IL-11 in the murine airway causes lymphocytic inflammation, bronchial remodeling, and airways obstruction

Interleukin-11 is a pleotropic cytokine produced by lung stromal cells in response to respiratory viruses, cytokines, and histamine. To further define its potential effector functions, the Clara cell 10-kD protein promoter was used to express IL-11 and the airways of the resulting transgene mice were characterized. In contrast to transgene (-) littermates, the airways of IL-11 transgene (+) animals manifest nodular peribronchiolar mononuclear cell infiltrates and impressive airways remodeling with subepithelial fibrosis. The inflammatory foci contained large numbers of B220(+) and MHC Class II(+) cells and lesser numbers of CD3(+), CD4(+), and CD8(+) cells. The fibrotic response contained increased amounts of types III and I collagen, increased numbers of alpha smooth muscle actin and desmin-containing cells and a spectrum of stromal elements including fibroblasts, myofibroblasts, and smooth muscle cells. Physiologic evaluation also demonstrated that 2-mo-old transgene (+) mice had increased airways resistance and non-specific airways hyperresponsiveness to methacholine when compared with their transgene (-) littermates. These studies demonstrate that the targeted expression of IL-11 in the mouse airway causes a B and T cell-predominant inflammatory response, airway remodeling with increased types III and I collagen, the local accumulation of fibroblasts, myofibroblasts, and myocytes, and obstructive physiologic dysregulation. IL-11 may play an important role in the inflammatory and fibrotic responses in viral and/or nonviral human airway disorders.

Prevalence of possible undiagnosed asthma and associated morbidity among urban schoolchildren

OBJECTIVE

The extent to which urban children endure the symptoms and consequences of asthma without a physician diagnosis has not been well studied. Our objective was to obtain an estimate of the prevalence of possible undiagnosed asthma in a population of urban schoolchildren.

DESIGN AND METHODS

A population-based cross-sectional study was conducted in urban schoolchildren, grades 3 to 5. Undiagnosed asthma was defined as caretaker report of symptoms and/or bronchial hyperresponsiveness, defined as a 15% or greater drop in baseline forced expiratory volume in 1 second, after exercise challenge.

RESULTS

A total of 230 children (61% of those eligible) participated in the study. Forty children (17.4%; 95% Confidence interval (CI) = 12.5% to 22.3%) had reports of a physician diagnosis of asthma. Of these, 33 (14.3%; (95% CI = 9.8% to 18.9%) reported wheezing in the past 12 months. Among the remaining 189 eligible children, 11 (5.8%; 95% CI = 2.5% to 9.2%) met study criteria for undiagnosed asthma based on bronchial hyperresponsiveness (BHR). Another 16 (8.5%; 95% CI = 4.5% to 12.4%) met study criteria for undiagnosed asthma through modified American Thoracic Society symptom criteria. Overall, 27 children (27/189; 14.3%) fulfilled criteria for undiagnosed asthma. Children identified as having undiagnosed asthma were compared with children who had no BHR and no symptoms and who did not report a physician diagnosis of asthma (children without asthma). Children with BHR were more likely to have a report of allergies and eczema than children without asthma, odds ratios (OR) = 8.5 (95% CI = 2.4 to 30.7) and 6.4 (95% CI = 1.1 to 38.1), respectively. Children meeting symptom criteria were more likely to have a report of allergies, OR = 6.2 (95% CI = 2.0 to 19.1), and bronchitis, OR = 6.7 (95% CI = 2.0 to 22.4), and were also more likely to report sleep disruption, OR = 7.1 (95% CI = 2.3 to 21.8) and missed physical education classes, OR = 15.0 (95% CI = 4.8 to 46.7), compared with children without asthma.

CONCLUSIONS

We estimated a prevalence of 14.3% for possible undiagnosed asthma among urban schoolchildren, grades 3 to 5, through caretaker report of symptoms or BHR postexercise challenge. Children with undiagnosed asthma reported more atopic disease than children without asthma. In addition, children meeting symptom criteria for asthma reported more bronchitis, sleep disruption, and missed physical education classes than did those without asthma. These results suggest that rates of undiagnosed asthma may be high in this predominantly black school-age population.

Problems of measuring asthma prevalence

This review considers the issues involved in measuring the community prevalence of asthma, particularly in the context of international comparisons. We argue that there is no gold standard definition for measuring asthma prevalence, and discuss the currently available methods of case ascertainment. Prevalence studies, if they are to be generalizable, need to involve large sample sizes with high response rates. This necessitates methods that are simple, inexpensive and practicable, but also as sensitive and specific for asthma as possible. We discuss some of the issues that are specific to comparisons of asthma prevalence between diverse populations, and suggest that large surveys using written or video questionnaires of self reported symptoms validated in all of the target populations are the method of choice.

Prevalence of bronchial hyperreactivity as determined by several methods among Estonian schoolchildren

There is a lack of established criteria to identify asthma and bronchial hyperreactivity (BHR) in epidemiological studies, although both conditions appear to bear some relationship to atopy, at least in children. Recent studies indicate a low prevalence of atopy in former Socialist countries in Europe, yet the prevalence of BHR has been reported to be high. We have analysed the relationship between the outcome of various lung function tests, atopy and clinical symptoms of bronchial asthma in an epidemiological survey of Estonian 10-12 year old schoolchildren. Metacholine provocation test (four steps with the cumulative doses 100, 300, 700 and 1100 micrograms), exercise challenge test and PEF-variability over two weeks were done in 806 children in Tallinn (coastal, industrialised city) and 774 children in Tartu (inland, university town). A positive response to the metacholine challenge test was recorded in 19% in Tallinn and in 32% in Tartu (p < 0.001). A similar tendency was observed for a more than 15% decrease of FEV1 in the exercise challenge test, i.e. 6% in Tallinn and 18% in Tartu. There was only a weak relationship between BHR, as defined by either a positive metacholine challenge and/or exercise test, diagnosed asthma and reported wheezing. Thus, 47% of the wheezing children and 30% of the children with asthma had negative test results. Only 17% of the children with a positive metacholine challenge were atopic, as defined by at least one positive skin prick test. In conclusion, none of the methods employed to assess bronchial hyperresponsiveness were very useful for the identification of wheezing and asthmatic children in this epidemiological study. In contrast to the results of studies in Western Europe, most children with bronchial hyperreactivity in Estonia are not atopic.

Prior diagnosis and treatment of patients with normal results of methacholine challenge and unexplained respiratory symptoms

OBJECTIVE

Previous research indicates that asthma has been underdiagnosed. However, we suspect that recent widespread attention to the underdiagnosis of asthma has led to an overdiagnosis of asthma in some settings. We therefore sought to examine prior diagnosis and treatment of patients referred to our facility and subsequently found to have no objective evidence of variable airflow limitation.

DESIGN

Retrospective chart review.

SETTING

Hospital-based asthma center.

PATIENTS

A referred sample of 263 patients in whom a methacholine challenge (MCC) was conducted after evaluation by our pulmonologists; complete medical histories were available.

MAIN OUTCOME MEASURES

Prior respiratory diagnoses, duration of treatment with asthma medications, and diagnosis following assessment by our pulmonologists in 175 patients with a provocative concentration of the substance causing a 20% fall in FEV1 (PC20) greater than 8.0 mg/mL and 88 with a PC20 of 8.0 mg/mL or less.

RESULTS

Of those with a PC20 greater than 8 mg/mL, a diagnosis of asthma or possible asthma prior to the challenge study was recorded by their primary care physician in 129 patients (74%). One hundred sixty of 172 patients (88%) with a PC20 greater than 8 mg/mL were diagnosed as not having asthma by our pulmonologists; 109 of 172 patients (62%) had been previously treated with asthma medication(s). The mean duration of asthma treatment was 25.9+/- 56.3 months, and there was no significant difference in the duration of treatment between this group and those who had a PC20 of 8 mg/mL or less. Most of those treated received inhaled beta2-agonists and inhaled corticosteroids. Approximately 61% received two or more classes of medications.

CONCLUSIONS

The misdiagnosis of asthma occurs commonly in the referral practice of a tertiary care asthma center. The more frequent use of objective pulmonary function testing in primary practice might reduce the problem of delayed diagnosis and inappropriate therapy for respiratory symptoms.

Relationship of non-specific airway hyperresponsiveness (AHR) to measures of peak expiratory flow (PEF) variability

BACKGROUND

The relationship between airway hyper-responsiveness (AHR) and clinical asthma remains controversial and unclear.

AIMS

To test the hypothesis that serial measures of variability of peak expiratory flow rate (PEF) correlate with serial measures of AHR, and to determine which mathematical expression of variability provides the best correlation.

METHODS

A longitudinal study over 180 days of 20 atopic, moderately severe asthmatics was undertaken. A diary of medication use and morning and evening PEFR before and after beta agonist was kept and AHR (PD20 histamine) was measured at three-weekly intervals. Using group data (128 sets) in PD20 was correlated with various measures of PEF variability over 9 days.

RESULTS

[Table: see text] Within the group there was a weak but highly statistically significant correlation between AHR and measures of PEF variability--the strongest correlation being with mean morning PEF. Within individual subjects, however, the correlation was not a consistent finding and only four patients had a statistically significant relationship (p < 0.05) between AHR and mean morning PEF.

CONCLUSIONS

These results suggest that while PEF variability may reflect AHR for the purposes of epidemiologic studies, it is unlikely to be useful as a simple 'non-invasive' means of assessing AHR in individual patients. More complex measures of PEF variability do not have an advantage over simpler measures such as mean morning PEF.

Are asthma-like symptoms due to bronchial or extrathoracic airway dysfunction?

Patients with asthma-like symptoms may not have asthma but obstruction of the extrathoracic airway (EA). To evaluate if dysfunction of the EA causes asthma-like symptoms, we assessed bronchial and EA responsiveness to inhaled histamine in 441 patients who presented with at least one of three key symptoms--cough, wheeze, dyspnoea--but had neither documented asthma nor bronchial obstruction. The histamine concentrations causing a 20% fall in forced expiratory volume in 1 s (PC20FEV1) and a 25% fall in maximal mid-inspiratory flow (PC25MIF50) were used as respective thresholds of bronchial and EA responsiveness. Values 8 mg/mL or less indicated bronchial (B-HR) or EA hyper-responsiveness (EA-HR). The influence of concurrent upper respiratory tract diseases, such as post-nasal drip (PND), pharyngitis, laryngitis and sinusitis, was also assessed. We found four response patterns to the histamine challenge: EA-HR in 26.5% of the patients, B-HR in 11.1%, combined EA-HR and B-HR in 40.6%, and no-HR in 21.8%. Cough was reported by 79% of the patients, wheeze by 53%, and dyspnoea by 40%. Patients with cough as the sole presenting symptom (34.2%), as compared with those with wheeze and/or dyspnoea (20%), had significantly greater probability of having EA-HR (OR 5.35, 95% CI 3.25-8.82) and lower probability of having B-HR (OR 0.45, CI 0.28-0.70); patients with cough plus wheeze and/or dyspnoea (45.8%) had significantly greater probability of having both EA-HR and B-HR than either those with cough alone (OR 2.48, CI 1.49-4.13), or those with wheeze and/or dyspnoea but not cough (OR 1.74, CI 1.36-2.22). EA-HR alone or combined with B-HR was strongly associated with EA diseases, particularly pharyngitis and PND. Cough was significantly associated with PND, either when it was the sole symptom (OR 2.16, CI 1.14-4.09) or when it was combined with wheeze and/or dyspnoea (OR 3.53, CI 1.97-6.33). Our results suggest that extrathoracic airway dysfunction may account for asthma-like symptoms, particularly chronic cough. This abnormality seems to be sustained by chronic diseases of the upper respiratory tract.

Prevalence of asthma and asthma symptoms in a general population sample from northern Italy. European Community Respiratory Health Survey--Italy

The European Community Respiratory Health Survey is an international survey of the general population which aims to establish whether there are significant variations in the prevalence of asthma among European countries. The present paper reports the prevalence of asthma and asthma-like symptoms in a sample of subjects living in three areas of northern Italy: Turin, Pavia, and Verona. Samples of residents 20-44 years old (3000 subjects in Turin and Verona and 1000 in Pavia) stratified by sex (M:F = 1/1) were randomly selected from local health authority lists in the three participating areas. To correct the observed prevalence estimate for nonresponse bias, a method proposed by Drane was applied. Of the sampled subjects, 86% (6031) participated in the survey. Two different definitions of asthma were adopted: 1) prevalence of asthma attack in the last 12 months; 2) prevalence of asthma attack or treatment with antiasthmatic drugs, or both wheezing apart from the common cold and wheezing with shortness of breath. This combination of symptoms has been called current asthma. According to these definitions, the prevalence of asthma attack was 3.47% (3.74% in men and 3.14% in women), and the prevalence of current asthma was 5.01% (5.07% in men and 4.90% in women). The lowest prevalence was found in Pavia; the highest in Turin. Our findings support the hypothesis that the difference in prevalence reflects the difference in mortality.

Comparison of airway reactivity induced by cold air and metacholine challenges in asthmatic children

Bronchial responsiveness to isocapnic hyperventilation with cold air (CAH) and to inhaled methacholine (MCH) was compared in 17 children with bronchial asthma. The response to cold air was expressed as the percent drop in FEV1 from baseline at 4 min. after the challenge (delta % FEV1 CAH), and the response to methacholine as the provocative concentration required to reduce the FEV1 by 20% from baseline (PC20MCH). Both tests were sensitive (94%) for detecting airway hyperreactivity. There was no statistically significant relationship between delta % FEV1 CAH and the log PC20MCH (r = 0.39; P = 0.12). In clinical practice, methacholine test is easier to perform, but in the research field cold air challenge may be preferable because it avoids potential drug effects.

Longitudinal study of the health of cotton workers

OBJECTIVES

To follow up a group of newly employed workers in a cotton mill, and to report changes in symptoms over time.

METHODS

A group of 110 mill workers at a cotton mill in Shijiazhuang, China, was investigated by questionnaire, skin testing, and spirometric measurements of airway responsiveness through forced expiratory volume in one second (FEV1). The workers were examined before starting work, at 10 weeks, and at one year.

RESULTS

Decreases in FEV1 over shifts were small at 10 weeks and one year, and slightly higher among people with skin reactions to cotton dust extracts. Airway responsiveness, defined as the average decrease in FEV1 after 1.25 mg methacholine was increased at 10 weeks. It remained about the same after one year, except in the workers positive for the skin test, in whom it was further increased. Subjective symptoms of chest tightness and cough with phlegm increased progressively at 10 weeks and one year; nasal irritation remained unchanged and dry cough decreased between 10 weeks and one year.

CONCLUSION

The results suggest that the airway inflammation caused by cotton dust increases with increasing exposure time and that the changes are more notable in workers with reactivity to cotton dust extract.

Bronchial responsiveness and symptoms in 5-6 year old children: a comparison of a direct and indirect challenge

BACKGROUND

The level of bronchial responsiveness in those with definite asthma correlates with disease severity and markers of airway inflammation. However, in population studies no clear distinction between normal and abnormal is found. Since the outcome of wheeze in early childhood is very variable, a marker of underlying airway inflammation would be of practical value. A stimulus acting indirectly may be more appropriate than one acting directly on smooth muscle. In this study the airway response to a direct (methacholine) and indirect (hypertonic saline) challenge have been compared in 5-6 year old children with past or present wheeze to see if symptom patterns or severity could be distinguished by either test.

METHODS

Forty children with a wide spectrum of wheeze were monitored for a six month period after which their pattern and severity of symptoms were graded. Hypertonic saline and methacholine challenges were then performed on separate days. The response was assessed by both respiratory resistance (Rrs6) and transcutaneous oxygen (PTCO2). Atopic status was determined by IgE and skin prick tests.

RESULTS

The results of both challenges were similar whether assessed by Rrs6 or PTCO2. There was no difference in the response to either methacholine or saline between different symptom patterns or severity grades, nor was there any correlation with either test to atopic status.

CONCLUSIONS

Neither an indirect nor a direct challenge distinguished between past or present wheeze or degree of clinical severity in this group of children. Either wheezy children of this age do not have airway inflammation or bronchial responsiveness is not a marker for it.

Gas trapping as a predictor of positive methacholine challenge in patients with normal spirometry results

Methacholine challenge studies are often conducted to diagnose asthma in patients with mild or intermittent respiratory symptoms when screening spirometry results are normal. We hypothesized that in patients with increased nonspecific bronchial hyperreactivity (NSB-HR), gas trapping might be present and that this information could be a factor in clinical decision making. To assess the relationship between gas trapping and NSBHR, we conducted a retrospective chart review of 500 patients who had undergone pulmonary function testing, including lung volume measurement and methacholine challenge. Measurements of airflow, lung volumes, and methacholine PC20 values were compiled and analyzed. FRC was determined by body plethysmography (FRCB) and by helium dilution (FRC-He). FRCB-FRC-He, RV (percent of predicted) RV/TLC, and RV/TLC (percent of predicted) were used as measures of gas trapping. RV% and RV/TLC% were the best predictors of a PC20 < or = 8 mg/mL. In the subset of 169 patients who had FEV1/FVC > or = 90% of pred, an RV/TLC% value of 125% of predicted or greater had a positive predictive value of 62.5% and a negative predictive value of 62.0%. RV/TLC% was the only measure of gas trapping that was associated with a PC20 < or = 8 mg/mL (p < 0.05). Linear regression revealed no correlation between any measure of gas trapping and quantified PC20 value (< or = 16 mg/mL). These results suggest that patients with a normal FEV1/FVC who show gas trapping have an increased likelihood of a positive methacholine challenge study. Furthermore, in these patients, RV/TLC (percent of predicted) is the best predictor of a positive methacholine challenge and this parameter may be useful in raising the clinical suspicion of asthma in the large population of patients presenting with respiratory symptoms and normal flow rates.

Prevalence of respiratory symptoms in Swiss children: is bronchial asthma really more prevalent in boys?

Precise epidemiological data for the prevalence of childhood asthma were lacking for Switzerland until recently. In 1990 we performed a stratified cluster sampling of schoolchildren (aged 7, 12, and 15 years), using a parent completed questionnaire to obtain data for the 12 months prevalence of asthma symptoms and the lifetime prevalence of asthma diagnosis. A response rate of 97.5% enabled us to analyse 4,353 completed questionnaires. The prevalence of any asthma symptom during the last 12 months was 17.5% while only 4.8% of the children reported the diagnostic label "asthma". The 12 months prevalence of chronic night cough was 12% and is comparable to other European data. Wheeze (5.9%) was reported less often in Switzerland than in England. At the age of 7 years asthma symptoms such as wheeze, morning tightness, and allergen-induced symptoms were reported more often in boys than in girls; at the age of 12 and 15 the male preponderance was no more evident. For all asthma symptoms the male-female ratio decreased with increasing age of the children, while independently of age twice as many boys than girls reported the diagnostic label "asthma." We conclude that asthma symptom prevalence in Swiss schoolchildren is within the lower range of European data. Chronic night cough might be a more appropriate variable to compare prevalence rates between regions with different cultural and linguistic backgrounds that the symptom of wheeze. Evidence exists for a substantial underdiagnosis of bronchial asthma in Swiss children, especially in girls. Further evaluation is needed to define risk factors for underdiagnosis and the associated risk for undertreatment.

Major reduction in asthma morbidity and continued reduction in asthma mortality in New Zealand: what lessons have been learned?

Increasing financial barriers to primary health care against a background of social and economic decline are likely to have contributed to asthma morbidity and mortality in New Zealand. Although there would not have been a sufficient increase in asthma prevalence to have accounted for the threefold increase in mortality rates, whether or not there was an increase in asthma severity in the late 1970s remains open to debate. Misuse or poor use of newly available and potent bronchodilator medications by those with the most severe asthma may simply have contributed to further delays in obtaining appropriate care and therefore to an increase in frequency of severe attacks in the community. Despite substantial increases in the use of bronchodilator therapy in New Zealand, there was no immediate improvement in indices of either asthma morbidity or mortality. The initial reduction in mortality rates in the 1980s happened at a time when first admissions for asthma were still increasing and seems to be best explained by an improvement in utilisation of hospital services (which were free until 1992) rather than a reduction in asthma severity. However, the recent reductions in all measures of asthma morbidity and further reduction in asthma mortality since 1989 does now suggest a reduction in asthma severity and would be best explained by the substantial increase in medium and high dose inhaled corticosteroid use, and to the endorsement of the current management strategies for asthma which are being promoted internationally and which were given considerable publicity in New Zealand in 1989 and 1990. Whilst sales of inhaled beta agonists were higher in 1991 than 1989, this may not reflect their pattern of use by individual patients since the need for an increase in inhaled beta agonist treatment has been accepted as indicating a lack of control and the need for either starting or increasing the dose of inhaled steroid treatment.

Asthma treatment, perceived respiratory disability, and morbidity

An entire school year of 8-9 year old schoolchildren in Sheffield were surveyed using the core questions of the international study of asthma and allergies in childhood in order to assess the morbidity associated with diagnosed asthma. Of 5321 children surveyed, replies were obtained from 4539 (85.3%). A current diagnosis of asthma was reported in 466 (10.3%), and a further 6.4% reported symptoms compatible with significant undiagnosed asthma. A validated questionnaire was used to assess symptoms and perceived disability in 336 (72.1%) of the children with diagnosed asthma. One third reported symptoms every day or most days, while 15.3% reported frequent nocturnal symptoms. There was no significant difference in reported symptoms between those receiving inhaled steroids, sodium cromoglycate, or no prophylaxis. Despite this, parents of children receiving inhaled steroids perceived more disability, and worried more about their children's health. It is concluded that perceived symptoms and morbidity are high in children with diagnosed asthma, and speculate that level of treatment is determined by parental tolerance of symptoms as much as by the symptoms themselves.

The relationship between respiratory symptoms and bronchial hyperresponsiveness in a population-based sample of adolescents and young adults

OBJECTIVES

to study the relationship between chronic respiratory symptoms and bronchial hyperresponsiveness (BHR) in adolescence and young adulthood and to assess the possible predictive value of these symptoms for BHR.

METHODS

a cross-sectional analysis: in a population sample of 551 subjects aged 10-23 years, data collected with a standardized questionnaire on respiratory symptoms were compared with the results of a histamine challenge test.

RESULTS

43% of the subjects reported one or more chronic respiratory symptoms; of these subjects 54% did not show BHR. Forty-two per cent of the subjects had a PC20 < or = 8.0 mg ml-1 histamine, of which 53% reported no chronic respiratory symptoms. Wheezing and breathlessness were related to the level of BHR, but only 'breathless when walking on the flat' was independently related to BHR; however, its predicted value for BHR was negligible.

CONCLUSIONS

in adolescents and young adults the relationship between chronic respiratory symptoms and BHR is incomplete. A standardized questionnaire on respiratory symptoms does not provide adequate information to discriminate between those with and without BHR.

Comparison of stayers, dropouts, and newcomers in a longitudinal population study of asthma and bronchial hyperresponsiveness: introduction of bias?

A random sample of children and adolescents from the general population in Copenhagen, Denmark, has been examined twice (6 years apart) with respect to asthma, allergy, and nonspecific bronchial hyperresponsiveness. To investigate potential bias resulting from loss of baseline subjects at follow-up (dropout bias) and bias resulting from subjects entering the study at the follow-up stage (newcomer bias), stayers (subjects who participated in both examinations) were compared to dropouts and newcomers, respectively. The sample consisted of 983 subjects (aged 7-17 years at the time of the baseline study), of whom 408 (199 boys) participated in both examinations (stayers), 119 (62 boys) in the baseline study only (dropouts), and 257 (124 boys in the follow-up study only (newcomers). Thus, a total of 784 subjects (80% of the sample) were examined either once or twice. At baseline dropouts did not differ from stayers with respect to anthropometric data, smoking habits, pulmonary function, or prevalence of positive skin prick tests, bronchial hyperresponsiveness, asthma, and allergic diseases. Likewise, these variables for newcomers were not different from those of the stayers apart from a significantly higher smoking rate in newcomers (45% vs. 32%, p = 0.003). Based on these findings and the high overall response rate, it seems reasonable to assume that the group of stayers is representative of the whole sample, apart from an underestimation of the number of smokers and, therefore, an underestimation of the risks associated with smoking.(ABSTRACT TRUNCATED AT 250 WORDS)

Bronchial reactivity and work-related symptoms in farmers

Work-related respiratory symptoms and bronchial reactivity were studied in 76 never-smoking farmers and in a control group not exposed to organic dusts. The farmers were divided into those working with vegetables/grain crops, animals but not swine, and with swine. The extent of symptoms was evaluated using a specific organic dust questionnaire. Bronchial reactivity was assessed with the methacholine challenge test. An increased incidence of organic dust toxic syndrome (ODTS), mucous membrane irritation (MMI), and chronic bronchitis (CB) was found among farmers working with swine or other animals. Pulmonary function baseline values were normal. Bronchial reactivity was increased and related to subjective symptoms of MMI and CB. There was also a relation between fatigue at work and bronchial reactivity.

Variability of peak expiratory flow rate in children: short and long term reproducibility

BACKGROUND

Variability of peak expiratory flow (PEF) has been proposed as a surrogate for bronchial hyperresponsiveness. The normal range of variability of PEF for children has been reported and the test has been used to screen for asthma in population based studies. However, there is little information on the reproducibility of the method in epidemiological settings.

METHODS

In a cohort study of primary school children the variability in PEF was recorded in two consecutive years for one week (first survey) and two weeks (second survey) using mini Wright peak flow meters. PEF was recorded twice daily (morning and evening) and average amplitude as a percentage of mean was calculated as a standard measure of PEF variability for each single week of PEF measurement. Children with PEF variability exceeding the 90% percentile of the distribution for the specific time period were regarded as having increased variability of PEF.

RESULTS

Of 66 children with increased PEF variability in the first year, 13 (19.7%) had an abnormal test in the first week of the second year. Of 543 children with normal PEF variability in the first year, 44 (8.1%) had an abnormal test in the second study year (odds ratio 2.8, confidence interval (CI) 1.4 to 5.4). Of 646 children in the second survey 61 (9.4%) were abnormal during the first week and 68 (10.5%) had an increased PEF variability during the second week, but only 24 (3.7%) children had an increased PEF variability in both weeks. The sensitivity (specificity) for doctor-diagnosed asthma (12 month period prevalence) was 36.4% (91.0%) in the first week of the second survey. When measurements of both weeks of the second survey were used to calculate PEF variability there was little improvement in the sensitivity (38.1%) and specificity (91.5%), mainly because of decreased compliance in the second measurement week.

CONCLUSIONS

In young children assessment of PEF variability in order to screen for asthma is of limited value because of the low reproducibility of the method.

Bronchial responsiveness in patients on regular hemodialysis treatment of very long duration

Several mechanisms (trapping of neutrophils, increased extravascular lung water, left ventricular hypertrophy, metastatic lung calcification, and iron deposition) may impair pulmonary function and alter bronchial responsiveness in patients on long-term regular dialysis treatment (RDT), but no studies have been published concerning patients on RDT for a very long time. To assess bronchial reactivity, a methacholine inhalation test was performed 2 to 24 hours after a dialysis session in 19 patients with RDT duration of almost 20 years (221 +/- 26 months) (group 1) and in 14 patients on RDT for a shorter time (24 +/- 22 months) (group 2); all patients had normal standard pulmonary function test results (group 1: forced vital capacity, 95% +/- 13% and forced expiratory volume in one second [FEV1]: 97% +/- 17%; group 2: forced vital capacity, 108% +/- 11% and FEV1, 108% +/- 9% of expected values). The methacholine provocation dose causing a 20% decrease in FEV1 was significantly lower than normal in seven (37%) group 1 patients and only in one (7%) group 2 patient; this difference was statistically significant (P = 0.049). There were no correlations between bronchial hyperresponsiveness and interdialysis weight gain, left ventricular hypertrophy, diastolic dysfunction expressed as the ratio between early diastolic filling and filling during atrial contraction, secondary hyperparathyroidism, and iron overload. Therefore, bronchial hyperresponsiveness is present in a substantial percentage of patients on RDT of very long duration, but the cause is unknown.

Atopic sensitization and respiratory symptoms among Polish and Swedish school children

Allergic sensitization and symptoms from the airways in relation to air pollution were compared in 10-12-year-old school children (n = 1113) from urban Konin in central Poland and both urban and rural parts of Sundsvall in northern Sweden. The measurements included parental questionnaires, skin-prick tests and serial peak flow measurements during 2 weeks with simultaneous monitoring of outdoor air pollutants. The skin-prick test technique was validated by IgE antibody determinations. The levels of common industrial pollutants, SO2 and smoke particles were much higher in Konin than in urban Sundsvall and the levels of NO2 were similar. Various respiratory symptoms were more often reported among school children in Konin (except for wheezing and diagnosed asthma). Multiple logistic regression analyses yielded the following increased odds ratios for children in Konin as compared with the reference group (rural Sundsvall): chest tightness and breathlessness 3.48 (95% confidence interval 2.08-5.82), exercise-induced coughing attacks 3.69 (95% confidence interval 1.68-8.10), recurrent episodes of common cold 2.79 (95% confidence interval 1.53-5.09) and prolonged cough 4.89 (95% confidence interval 2.59-9.23). In contrast, as compared with rural Sundsvall, the adjusted odds ratio for a positive skin-prick test was decreased in Konin, but increased in urban Sundsvall, 0.58 (95% confidence interval 0.37-0.91) and 1.67 (95% confidence interval 1.15-2.42) respectively. The study confirms that living in urban, as compared with rural areas, is associated with an increased prevalence of respiratory symptoms and sensitization to allergens. These differences could be explained by air pollution. Respiratory symptoms were more common in a similar urban group of Polish children who were exposed to even higher levels of air pollution. These children, however, had a much lower prevalence of sensitization to allergens, as compared with the Swedish children. This indicates that differences in lifestyle and standard of living between western Europe and a former socialist country influences the prevalence of atopy.

Asymptomatic bronchial hyperreactivity and the development of asthma and other respiratory tract illnesses in children

BACKGROUND

It is not clear whether asymptomatic bronchial hyperresponsiveness (BHR) in children is a risk factor for the subsequent development of asthma. A longitudinal study was conducted to determine the predictive value of BHR for the development of asthma in a primary care patient population.

METHODS

A standard free running asthma screening test (FRAST) was applied to 956 schoolchildren aged between 4 and 11 years in 1985. Peak expiratory flow (PEF) rates were measured before hard running for six minutes and following a three minute rest period. Children with a fall in PEF of more than 15% were labelled as having a positive FRAST. Clinical data from the patients' notes and from symptom questionnaires were compared with age and sex matched controls for children known to have asthma, and for those with a positive FRAST but no asthma (BHR group). Over the ensuing six years to 1991 further clinical data were gathered to compare the development of asthma and other diseases of the airways in both the BHR groups and their controls.

RESULTS

Of the 956 children exercised in 1985, 60 who were not known to have asthma had an abnormal test. Of the 55 of these studied in 1991, 32 (58%) had developed asthma. The sensitivity of a positive FRAST for the development of asthma was 58%, its specificity 97%, and positive predictive value 72%. Hay fever, eczema, otitis media, "bronchitis," and family history of atopy also occurred more commonly in this group.

CONCLUSIONS

Asymptomatic BHR, as shown by exercise challenge, can predict the development of clinical asthma. This study has also shown a relation between BHR, asthma, and other diseases of the airways, notably upper respiratory tract infection, "bronchitis," and otitis media.