Specific airway resistance is a better outcome parameter in bronchial provocation testing compared to FEV1 in patients with bronchial asthma

OBJECTIVES: Asthma is a chronic inflammatory disease characterized by airway hyperresponsiveness (AHR). A bronchial provocation test (BPT) is used to test for AHR. However forced expiratory volume in one second (FEV1), used as outcome parameter is effort-related, in contrast to specific airway resistance (sRaw). This research was conducted to provide insight in the usefulness of sRaw as an outcome parameter in BPT.

METHODS: A total of 85 patients performing a BPT were included in the study. Bronchial reactivity was defined as the provocative dosage or provocative concentration causing a 20% decrease in FEV1 (PC-20) or a 100% increase in sRaw (PC+100).

RESULTS: No significant response in either FEV1 or sRaw was found in 20 patients (24%). Twenty-nine patients (34%) only had a positive response for sRaw; 24 out of these 29 patients recognized their symptoms. 36 patients (42%) showed a positive response for both PC-20 and PC + 100.

CONCLUSIONS: Twenty-nine patients (34%) showed a significant increase in sRaw without a fall in FEV1. As performing sRaw is not a routine investigation, these patients are at risk of being excluded from a diagnosis of asthma. We suggest performing sRaw for patients without a fall in FEV1 during BPT when they report recognizable symptoms.