Asthma, Asthmalike Symptoms, Chronic Bronchitis, and the Degree of Bronchial Hyperresponsiveness in Epidemiologic Surveys

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Abstract
Measurement of bronchial hyperresponsiveness has been suggested to be a useful test in identifying subjects with asthma in epidemiologic groups. We explored the association between the degree of bronchial hyperresponsiveness, respiratory symptoms suggestive of asthma, chronic bronchitis, and various definitions of asthma based upon information obtained from a questionnaire. We determined bronchial hyperresponsiveness by methacholine inhalation test, administered a standardized respiratory questionnaires, and performed spirometry on 1,392 male workers in various industries: 229 (16.5%) had PC20 less than 8 mg/ml, 66 (4.7%) and PC20 less than 2 mg/ml, and 8 (0.6%) had PC20 less than 0.5 mg/ml. Only 760 workers had no respiratory symptoms; no workers with PC20 .ltoreq. 0.5 mg/ml, 31.0% of workers with PC20 > 0.5 but .ltoreq. 2 mg/ml, and 38.0% of workers with PC20 > 2 but .ltoreq. 8 mg/ml had no chest symptoms. Those reporting wheeze or breathlessness, and especially those with both symptoms, were significantly more likely to have bronchial hyperresponsiveness with a low PC20. The reporting of chest tightness did not influence this relationship, and there was no difference between the occurrence of "wheeze without a cold" and "persistent wheeze". Although there was a stronger association of PC20 .ltoreq. 2 mg/ml with asthma than with chronic bronchitis, the association of PC20 > 2 and .ltoreq. 8 mg/ml was not different with asthma than with chronic bronchitis. Bronchial hyperresponsiveness was more closely associated with asthma than with any asthmalike symptoms ascertained by a questionnaire developed for the study of chronic bronchitis. Our conclusion was that identifying subjects with asthma by measurement of bronchial hyperresponsiveness in epidemiologic surveys is not straightforward, and therefore priority should be placed upon designing and validating an asthma questionnaire.