Noneosinophilic responders with occupational asthma: a phenotype associated with a poor asthma prognosis.
Lemiere-C; Chaboillez-S; Bohadana-A; Blais-L; Maghni-K
J Allergy Clin Immunol 2014 Mar; 133(3):883-885.e3
Asthma tends to be considered a syndrome comprising different phenotypes rather than a disease representing a homogeneous group of patients. There is growing evidence that the identification of asthma phenotypes could be crucial in improving not only our understanding of the disease but also its management.1 Although several phenotypes have been identified in asthma, there is very little information on occupational asthma (OA) phenotypes in the literature. We sought to assess whether the type of airway inflammation induced by the exposure to a sensitizer can allow the identification of distinct phenotypes of OA with a different clinical outcome. We performed a cross-sectional study of workers whose OA was diagnosed by specific inhalation challenges at Sacre-Coeur Hospital between 2000 and 2005 and who had sputum samples collected before and 8 hours after exposure to the offending agent at the time. These subjects were invited to attend a visit between 2010 and 2011 in which detailed medical and occupational questionnaires were administered. Questions were asked about their respiratory symptoms at work, asthma medication, smoking habits, and work environment. Asthma control was assessed by using the validated Asthma Control Questionnaire.2 Quality of life was assessed by using the Juniper specific asthma quality of life questionnaire.3 Skin prick testing,4 spirometry5 methacholine inhalation challenge,6 and sputum induction7 were performed. The fraction of exhaled nitric oxide was measured with chemiluminescent analyzers (280i Sievers; GE, Boulder, Colo) before performing spirometry.8 The study was approved by Sacre-Coeur Hospital's research ethics committee. All subjects gave their written consent. The originality of our study was to assess the inflammatory phenotype in response to the exposure to a specific agent. Although a positive asthmatic reaction is usually associated with an eosinophilic inflammation in subjects with OA, a noneosinophilic response is not uncommon because 40% of our subjects with an asthmatic reaction had a noneosinophilic response at diagnosis. Although an eosinophilic response is identified in the majority of the cases of inhalation challenges using common allergens, there is evidence that eosinophilic or mast cells are not always involved in late asthmatic reactions.9 This study has limitations that should be noted. Our sample size was limited, which prevented us from studying the effect of the type of agent on airway inflammation. We did not collect supernatant at the time of the diagnosis and thus, the mediators measured in the study were not associated with the airway inflammation induced by the exposure to occupational agents, preventing us from exploring the mechanism at the time of exposure. In conclusion, a noneosinophlic response associated with an asthmatic reaction occurring after exposure to an occupational agent seems associated with a poorer clinical outcome. Further studies are needed to assess the reproducibility of the noneosinophilic phenotypes and to determine whether alternative treatments can be offered to those subjects.
Bronchial-asthma; Occupational-diseases; Immune-reaction; Airway-resistance; Employee-exposure; Clinical-diagnosis; Clinical-tests; Health-surveys; Questionnaires; Work-environment; Respiratory-system-disorders; Exposure-assessment; Medical-screening; Skin-tests; Spirometry; Methacholines; Smoking; Respiratory-hypersensitivity; Humans; Men; Women; Physiopathology
Catherine Lemiere, MD, MSc, Centre de recherche de l'Hôpital du Sacré-Coeur de Montréal, Montréal, Quebec, Canada; and Université de Montréal, Montréal, Quebec, Canada
Journal of Allergy and Clinical Immunology
Sacre Coeur Montreal Hospital (Hôpital du Sacré-Coeur de Montréal)