FEV1 and sRaw in bronchial challenge testing, exchangeable or supplementaFEV1 and sRaw in bronchial challenge testing, exchangeable or supplemental?

Abstract

Introduction: A bronchial challenge test (BCT) with inhalation of histamine is used to test for airway hyperresponsiveness (AHR), however the measured forced expiratory volume in one second (FEV1) is effort-related. Assessing specific airway resistance (sRaw) is a more effort-independent procedure, however little is known about the correlation between FEV1 and sRaw. Aims and objectives: Our hypothesis is that assessing sRaw adds information to a BCT possibly leading to increased sensitivity in excluding asthma. Methods: All patients seen on the outpatient clinic with respiratory symptoms suggestive of asthma who performed a BCT using histamine were included in the study. Bronchial reactivity was defined as the provocative dosage/concentration at which a 20% decline in FEV1 was seen (PC20), or at which the airway resistance increased with 100% up to 200% (PC200). Results: 119 patients were evaluated, of which 15 were excluded due to insufficient data. 42 patients (40%) showed no significant response in FEV1 and sRaw, of which 21 had recognizable symptoms. 27 (26%) only had a positive response for sRaw, without a significant fall in FEV1. 26 reported recognizable symptoms. 3 patients (3%) had a response in FEV1 without showing an increase in sRaw. The remaining 32 patients (31%) had both a positive PC20 and PC200, all reporting recognizable symptoms. Conclusion: We found 27 patients (26%) with a significant increase in sRaw without a fall in FEV1, while reporting recognizable symptoms. Not measuring sRaw would wrongly exclude a diagnosis of asthma. This research suggests adding sRaw to FEV1 increases the sensitivity of BCT for AHR.