%0 Journal Article %A Jacques André Pralong %A Jocelyne L'Archevêque %A Manon Labrecque %A Catherine Lemière %A André Cartier %T Absence of nonspecific bronchial responsiveness (NSBR) in occupational asthma (OA): A case-series study %D 2012 %J European Respiratory Journal %P P1024 %V 40 %N Suppl 56 %X Background: Although increased NSBR is a key component of OA it may be absent in rare occasions as previously shown.Objective: Describe the prevalence of confirmed OA with normal NSBR before and after specific inhalation challenge (SIC).Methods: We retrospectively reviewed our database containing all SIC done in our laboratory or at work between 1997 and 2011. OA was defined by a positive SIC with a ≥20% sustained decrease in FEV1; normal NSBR was defined by PC20Methacholine (PC20M) >16 mg/ml.Results: 373/1193 workers tested had confirmed OA. 22/373 (5.9%) had normal NSBR before and after SIC. The mean±SD delay between cessation of exposure at work and SIC was 96.2±81.7 days. However, 10 subjects had at least one PC20M < 16 mg/ml during their investigation while symptomatic and at work for 9 of them. The remainder 12 had normal NSBR on all tests but only 3 subjects had such a test while at work (2 while symptomatic). Among the 22 cases, 20 were atopic, 15 were exposed to a high molecular weight agent, 4 to a low molecular weight chemical and 3 to various agents during workplace challenge. Seventeen, 4 and 1 subjects had an early, late and atypical asthmatic reaction respectively. However, even if NSBR was always within the normal range, 3 subjects had a significant drop in PC20M (> 3.2 fold) post-SIC and 13/14 showed an increase in sputum eosinophils count after SIC (mean increase of 9.9±16.7%).Conclusions: We describe 22 cases of confirmed OA despite normal NSBR before and after SIC. This is however rare (5.9% of confirmed cases of OA by SIC). In our experience, it is exceptional to have normal NSBR while symptomatic and at work in cases of confirmed OA. %U https://erj.ersjournals.com/content/erj/40/Suppl_56/P1024.full.pdf