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Phenotyping of chronic respiratory diseases in the South of Vietnam

par Chu Thi, Ha
Président du jury Casimir, Georges
Promoteur Michel, Olivier
Co-Promoteur Corazza, Francis
Publication Non publié, 2019-06-25

Thèse de doctorat

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Résumé :

Chronic respiratory diseases (CRDs) include chronic diseases involving the airways and other structures of the lung. In the current circumstance of Vietnam, people are exposed to numerous risk factors of CRD, such as heavy smoking, high frequency of pulmonary tuberculosis, chronic helminthiasis, allergic factors, migration and urbanization (the last associated with traffic-related pollution). The phenotype diagnoses should take into account the risk factors of each individual besides the clinical features, while the differential diagnoses mostly depend on the available techniques in each healthcare center. Our aim was to improve the differential diagnoses of the 3 most frequent CRDs: chronic obstructive pulmonary disease (COPD), asthma and COPD – asthma overlap syndrome (ACOS), in Vietnam. In the first part, we evaluated the prevalence of the allergen sensitization among patients with CRD, in regard to the urban and rural area in the South of Vietnam. House dust mites and cockroach droppings were the most frequent sensitizer. Compared with participants born in the urban setting, those born in the rural environment were less frequently sensitized and this protective effect disappeared in the case of migration from rural to urban areas. In the second part, we evaluated skin prick test as a method to screen dust mite sensitization in CRD in southern Vietnam. The data suggested that, in the present circumstance, skin prick test can be used to screen mite sensitization. In the third part, we evaluated the risk of mite sensitization in the native and migrant population, in regard to several environmental factors. Consistently with the hygiene hypothesis, compared to urban, exposure to high endotoxin concentration in rural was a protective factor against allergic sensitization. We reported for the first time that this effect was reversible among the migrants from rural to urban setting in association with lower endotoxin exposure. In the fourth part, we have defined asthma, COPD and ACOS based on clinical symptoms, cumulative smoking and airway expiratory flow with reversibility, on one side, and the age-related of the different phenotypes, on the other side. We hypothesized that the cumulative exposure to noxious particles should increase the age-related prevalence of COPD, while due to the immunosenescence process, the prevalence of IgE-mediated asthma should decrease with age, and ACOS prevalence being not related to age due to the combined mechanisms.  In conclusion, we showed in the South of Vietnam that:1) mites and cockroach allergens were the most frequent sensitizer in chronic respiratory diseases;2) the skin prick test to mite has been validated to screen mite sensitization;3) associated with a reduced level of endotoxin level, migration from rural to the urban setting was a risk factor of mite sensitization in chronic respiratory diseases;4) based on the clinical symptoms, spirometric values, and cumulative smoking, the diagnosis of asthma, COPD and ACOS have been made and their prevalence were 25, 42 and 33%, respectively.