Contribution of the Indoor Environment Medical Advisor in the Management of Fibrosing Hypersensitivity Pneumonitis

Hypersensitivity pneumonitis (HP) is a diffuse infiltrative pneumonitis (DIP) of immuno-allergic origin, caused by exposure to one or more antigenic substances of organic origin, in genetically predisposed individuals. It can take a fibrosing form, eventually leading to chronic respiratory failure. Diagnosis is based on a combination of clinical, biological, CT scan and histological evidence, and is made during multidisciplinary discussions (MDD) of diffuse interstitial lung disease.

The antigens responsible, of domestic or professional origin, may be micro-organisms, animal proteins or chemical agents. However, the antigen remains unknown in almost 50% of cases. Lack of antigen identification is an independent risk factor for death in patients with fibrosing HP. In fibrosing forms, corticosteroid therapy does not appear to improve functional prognosis, and ninedanib, an antifibrosing treatment offered in progressive forms, only slows functional decline. Identifying the causative antigen is therefore an essential element in the overall management of these patients, with the aim of implementing avoidance measures. A medical exposure questionnaire has been translated into French to help physicians identify the antigen.

The serum precipitin assay is a tool developed to help identify sensitization to an antigen. It is all the more useful when investigations are targeted at the patient's suspected exposure. However, their sensitivity and specificity are variable.

The activity of the indoor environment medical advisor (CMEI) has developed in the care of patients with chronic respiratory or allergic pathologies. Their role is to carry out an audit of the dwelling, take environmental measurements to assess the health risk, inform patients about appropriate eviction measures and, in some cases, refer patients to organizations specializing in home improvement.

The CMEI visits the patient's home. The environmental audit includes a rigorous macroscopic examination and microbiological swabs of visible anomalies. The CMEI can also supplement its analysis with electrostatic dust collectors, which are left in the home for 4 weeks, enabling both qualitative and quantitative characterization of antigens.

To date, no study has prospectively evaluated the contribution of CMEI to antigen identification in patients with fibrosing HP. At the Nantes University Hospital and Angers University Hospital, the environmental audit carried out by the CMEI is an integral part of routine patient management in the event of a HP diagnosis.

The main objective of this study is to measure the diagnostic contribution of the indoor environment medical advisor in the identification of antigens responsible for respiratory pathology in patients with fibrosing HP.