A comparison of spirometric measurements in allergen bronchial challenge testing

Abstract

The usefulness of several spirometric measurements were compared in detecting asthmatic reactions after allergen bronchial challenge in 14 asthmatic children. All of the children had a history suggesting mite-induced asthma and 11 had a 3 mm or larger diameter weal on prick testing with Dermatophagoides farinae extract. On bronchial challenge testing with dilutions of this extract 12 children had an early asthmatic reaction and 9 had a late asthmatic reaction. In decreasing order of sensitivity for detecting the early asthmatic reaction the tests ranked as follows: FEV1 [forced expiratory volume in 1 s], FEF[forced expiratory flow]50%, FEF25-75%, PEFR [peak expiratory flow rate] and FVC [forced vital capacity]. For the late asthmatic reaction the order was FEF50%, FEV1, FEF25-75%, PEFR and FVC. No single test identified all the early or all the late reactions but the FEV1, a test useful for indicating large airways obstruction, when combined with the FEF25-75%, a test influenced by small airways obstruction, detected all early and late asthmatic reactions. The FEF50% was a sensitive test but was the only 1 to become falsely positive. It became falsely positive in 4 patients. Although the FEV1 was the most useful single test it is, by itself, an inadequate indicator of the asthmatic reaction and should be used with the FEF25-75% to ensure the detection of all asthmatic reactions induced by allergen bronchial challenge testing.