Population based study of risk factors for underdiagnosis of asthma in adolescence: Odense schoolchild study.

OBJECTIVE: To describe factors related to underdiagnosis of asthma in adolescence. DESIGN: Subgroup analysis in a population based cohort study. SETTING: Odense municipality, Denmark. SUBJECTS: 495 schoolchildren aged 12 to 15 years were selected from a cohort of 1369 children investigated 3 years earlier. Selection was done by randomisation (n = 292) and by a history indicating allergy or asthma-like symptoms in subject or family (n = 203). MAIN OUTCOME MEASURES: Undiagnosed asthma defined as coexistence of asthma-like symptoms and one or more obstructive airway abnormalities (low ratio of forced expiratory volume in 1 second to forced vital capacity, hyperresponsiveness to methacholine or exercise, or peak flow hypervariability) in the absence of physician diagnosed asthma. Risk factors (odds ratios) for underdiagnosis. RESULTS: Undiagnosed asthma comprised about one third of all asthma identified. Underdiagnosis was independently associated with low physical activity, high body mass, serious family problems, passive smoking, and the absence of rhinitis. Girls were overrepresented among undiagnosed patients with asthma (69%) and underrepresented among diagnosed patients (33%). Among the risk factors identified, low physical activity and problems in the family were independently associated with female sex. The major symptom among those undiagnosed was cough (58%), whereas wheezing (35%) or breathing trouble (50%) was reported less frequently than among those diagnosed. Less than one third of those undiagnosed had reported their symptoms to a doctor. CONCLUSIONS: Asthma, as defined by combined symptoms and test criteria, was seriously underdiagnosed among adolescents. Underdiagnosis was most prevalent among girls and was associated with a low tendency to report symptoms and with several independent risk factors that may help identification of previously undiagnosed asthmatic patients.

Reduced forced expiratory flow in schoolchildren with respiratory symptoms: the Odense Schoolchild Study.

In the present population-based study, spirometric lung function was assessed in symptomatic schoolchildren with and without asthma as compared to an asymptomatic reference group. The primary aim was to investigate if impaired lung function could be demonstrated in symptomatic schoolchildren, even in the absence of diagnosed asthma. Spirometry [forced vital capacity (FVC), forced expiratory volume in 1 s (FEV1), 50% of forced expiratory flow (FEF 50%) and 75% of forced expiratory flow (FEF 75%)] and anthropometric measures (standing height, weight, skin fold thickness, and length and circumference of the upper arm) were obtained from 1369 8-10-year-old children (81.5% of the eligible population) during the school year 1985-86. In 1321 of those subjects (96.5% of those examined), a self-administered questionnaire was completed. Thirty-five children belonging to ethnic minorities were excluded, thus 1286 subjects were included for further analysis. Point prevalences concerning asthma and respiratory symptoms (wheeze, cough and shortness of breath) were obtained. Thirty-seven children reported asthma and one or more asthma-like symptoms (symptomatic asthmatics), whereas 40 children denied having asthma, although claiming one or more asthma-like symptoms (symptomatic non-asthmatics). In both symptomatic groups, FEF 50% and FEF 75% were reduced relative to the reference group, the deficit being larger in the symptomatic asthmatics. FEF 75% was found to be more reduced than FEF 50%. FEV1 and FVC did not differ significantly between groups. It is concluded that only half of the schoolchildren with respiratory symptoms usually associated with the presence of asthma actually reported having this disease. These results demonstrate the presence of reduced lung function in symptomatic, reportedly non-asthmatic, children, suggesting clinically important underdiagnosis of asthma. More severe impairment of lung function was found in known asthmatics, also implying some degree of undertreatment.

Interrelationships between diagnosed asthma, asthma-like symptoms, and abnormal airway behaviour in adolescence: the Odense Schoolchild Study.

BACKGROUND: The diagnosis of asthma is based on several characteristics including symptoms and suitable tests of airway lability. However, it is neither clear to what degree various tests and symptoms identify the same subjects, nor how these characteristics are best combined to diagnose asthma. The interrelationships between physician-diagnosed asthma, asthma-like symptoms, and abnormal airway function, as defined by four commonly used tests, have therefore been assessed. METHODS: A population based sample of 495 Danish schoolchildren aged 12-15 years, comprising 292 randomly selected subjects and 203 subjects considered at risk of having or developing asthma, was examined. Symptoms and background information were recorded by questionnaire. The test panel consisted of baseline forced expiratory volume in one second (FEV1%), provocation with treadmill exercise (EXE) and with inhaled methacholine (PD15), and monitoring of peak expiratory flow (PEF) twice daily for two weeks. RESULTS: The sensitivity for diagnosed asthma was highest for PD15 followed by PEF monitoring, whereas specificity for asthma or asthma-like symptoms was marginally higher with the other two tests. Most symptomatic subjects with any positive test were identified by PD15 alone (75%) or in combination with PEF monitoring (89%). PEF variability was more susceptible to treatment with inhaled steroids than the PD15 index. Although inter-test agreement was weak (kappa < 0.40 for all pairs), significant associations were found between PD15 and EXE, PEF and EXE, and FEV1% and PD15. CONCLUSIONS: The agreement between the four tests was weak. In particular, PEF variability and methacholine responsiveness seem to identify different varieties of airway pathophysiology. The combined use of methacholine provocation testing and PEF monitoring may be helpful as an epidemiological screening tool for asthma.

Evaluation of peak expiratory flow variability in an adolescent population sample. The Odense Schoolchild Study.

The validity of peak expiratory flow (PEF) recordings and the sensitivity of PEF variability indices in asthma and asthma-like conditions were examined in an adolescent population. Recordings from 245 randomly selected subjects and from an additional 181 subjects reporting or considered at risk for developing asthma were analyzed. Subjects recorded PEF twice daily for 2 wk using Mini-Wright meters, completed a symptoms questionnaire, and were tested for airway responsiveness to methacholine. The first three recording days showed significant accumulation of lowest PEF values recorded (41%) and were excluded from further analysis. Among nine PEF variability indices, the Two-lowest%mean (the mean of the two lowest PEF values as a percentage of the period mean) had the best sensitivity for physician-diagnosed asthma (28%). The sensitivity of the methacholine dose-response slope (DRS) was 69%. Combining these indices, a sensitivity of 77% for diagnosed asthma was obtained. Among subjects with asthma-like symptoms but no diagnosis of asthma, 14% had increased Two-lowest%mean and the DRS was increased in 17%, but only 3% were identified by both tests. In conclusion, inhomogeneity of PEF data could be corrected by disregarding the first three recording days. PEF variability indices identified some diagnosed asthmatics, and particularly some symptomatic "nonasthmatics," not identified by the DRS, suggesting that the combined use of these indices might be helpful.