Occupational Asthma Reference

Inman MD, Watson R, Cockcroft DW, Wong BJ, Hargreave FE, O'Byrne PM, Reproducibility of allergen-induced early and late asthmatic responses, J Allergy Clin Immunol, 1995;95:1191-1195,

Keywords: reproducibility, FEV1, power, ch, methods

Known Authors

Freddy Hargreave, McMaster University, Hamilton Freddy Hargreave

Don Cockcroft, Saskatoon Don Cockcroft

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BACKGROUND: Constant-dose allergen inhalation challenges are frequently used to examine the effect of antiasthma drugs on the allergen-induced early and late asthmatic responses. The end- point measurements in such studies are the maximal early and late percent decreases in the forced expiratory volume in 1 second (FEV1).

OBJECTIVE: Our purpose was to observe the reproducibility and to determine the sample sizes required for such studies.

METHODS: Twenty-eight subjects with allergen-induced early and late responses were studied with two constant-dose allergen challenges separated by 2 to 12 weeks. The early response was measured as the maximum percent decrease in FEV1 during the first 2 hours and the late response as the maximum percent decrease in FEV1 between 3 to 7 hours.
RESULTS: The mean +/- SEM early responses were 23.1% +/- 1.0% and 24.7% +/- 2.0%, whereas the mean late responses were 23.3% +/- 2.0% and 24.5% +/-2.2%. Reproducibility of measurements were such that fewer than eight subjects are required, to show 50% attenuation of either the early or late response (with 90% power).

CONCLUSIONS: The method of constant-dose allergen challenge is a sensitive tool for detecting changes in early and late asthmatic responses after the use of antiasthma medication 0 (Allergens)

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