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[Longitudinal study of bronchial hyperreactivity using the carbachol test with school children]
J Forster1, A Hendel-Kramer, K Weis
1Universitätskinderklinik Freiburg im Breisgau.
Study Design:
Bronchial hyperresponsiveness of 476 schoolchildren (10.8 +/- 2.3 years) was studied three times at 12 months' intervals. The cumulative dose of 400 micrograms carbachol was applied in 50 + 50 + 100 + 200 micrograms steps. A fall of FEV1 of at least 15% was regarded as positive reaction. The test was save, as no severe obstruction was observed, only three children withdrew because of unpleasant cough.
Results:
Reactivity was observed in 19.1, 10.0, and 5.2% of children at the occasion of the first, second and third test (sensitivity/specificity for prevalence of physician diagnosed asthma: 70/83, 35/91, and 24/96%, respectively). Reactivity was age dependent (7-11 years: 35%, 12-16 years: 18%), not influenced by sex, and the relative risk to be reactive was 1.9 in children 2-3 weeks after a respiratory tract infection.
Conclusion:
For epidemiological purposes carbachol provocation test--like other unspecific bronchial provocation tests--is inappropriate as a single test to classify individuals as asthmatics.