Bakers’ rhinitis : diagnostic criteria, flour dust exposure, mucosal inflammation, IgE sensitization, and relation to lower airways
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This thesis is the results of a cross-sectional epidemiological study undertaken in the period from March 2000 to January 2002 on bakery workers in 6 bakeries in Bergen, Norway. The aims were to study the consequences of different criteria for the diagnosis of occupational rhinitis (OcR), assess the prevalence of IgE sensitization, and to explore the relationships between OcR, upper and lower airway symptoms, IgE-sensitization, nasal indices of inflammation, bronchial responsiveness, and flour dust exposure. We have taken into account possible confounders such as age, gender, smoking, and baseline lung function, and we also present an alternative continuous outcome estimate of bronchial responsiveness. Bakery workers (n=197) were subjected to interviews, questionnaires, workplace dust measurements, allergy tests, and nasal lavages with and without histamine provocation. The criteria for the diagnosis of OcR were based on the International Consensus Report on Rhinitis (ICR) from 1994. α2-Macroglobulin and eosinophil cationic protein (ECP) were measured in nasal lavage fluid. Bronchial provocation test with metacholine was carried out according to the American Thoracic Society’s guidelines. Bronchial responsiveness was expressed as slopeconc, a measurement derived by regressing the percent reduction in FEV1 at each provocation step. The prevalence of OcR varied between 23 and 50% depending on the diagnostic criteria used. OcR, both IgE- and non-IgE-mediated, was associated with asthma symptoms. The most frequent causes of sensitization were various species of storage mites (20%). Storagemite sensitization was related to both OcR and work exposure (production workers versus administrative staff). α2-Macroglobulin, ECP, and the exudative responsiveness to histamine increased significantly with increasing workplace dust exposure (p≤ 0.035). Similar patterns were seen in workers with OcR and with work related rhinitis symptoms, but occupational sensitization was not a discriminating factor. Bronchial hyperresponsiveness (BHR) expressed as slopeconc was associated with smoking (p=0.017) and asthma symptoms at work (p=0.003), but not with IgE sensitization to occupational allergens (p=0.221) when we also adjusted for baseline lung function. We demonstrated an association between ECP in nasal lavage and BHR in a subgroup where BHR was defined as slopeconc < 3 (p=0.012). No association was seen between bronchial responsiveness and current exposure level of flour dust, nasal symptoms, and a diagnosis of OcR. Using different diagnostic criteria have considerable consequences for the prevalence of OcR. There is a strong relationship between OcR and lower airway symptoms. Storage mites maybe important occupational allergens in Norwegian bakeries. OcR and occupational dust exposure in bakery workers is associated with nasal eosinophilic exudative inflammation. In contrast, occupational sensitization is not a discriminating factor with regard to nasal indices of eosinophilic, exudative inflammation. Bronchial hyperresponsiveness measured by metacholine provocation is related to baseline lung function, smoking, work related asthma symptoms, and nasal eosinophil activity, but not to occupational IgE sensitization. The slopeconc expression seems to be a useful continuous outcome in bronchial responsiveness testing with metacholine.