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Identification of indoor fungal antigens in assessment of hypersensitivity pneumonitis – an alternate approach

Background: The diagnosis of hypersensitivity pneumonitis (HP) onset after fungal antigens inhalation at home can be challenging. Although an early identification of the inhaled antigen and its complete avoidance are recommended, current strategies for identifying the causal antigen are controversial. Objective: To determine the usefulness of this diagnostic strategy in detecting potentially causative fungal agents in the patient’s home environment. Methods: We selected 8 patients with a multidisciplinary diagnosis of HP in our Interstitial Lung Disease Program at a tertiary referral center. All patients had their serum tested against the standard HP screening antigen panel with a positive antibody response, but without an identified antigen based on patient interviews. A standardized environmental sampling took place at each patient’s home. Results: Up to 64 air and swabs samples (median=40; Interquartile range=17) were collected from each patient’s environment. High numbers of colony-forming units (CFU) (more than 100 CFU/plate or more than 100 CFU/ml) of different species of fungi were identificated in each patient’s home. The most prevalent species were Penicillium spp and Cladosporium herbarum. All the individuals had a positive response on the standard antigens panel to more than 1 antigen from the environmental sample. After identifying the possible causative factor, an exhaustive cleaning and remediation of the affected areas were made. Conclusion: An indoor environmental study may be crucial to avoid the continuation of unrecognized exposure to the causative fungal antigen. This might contribute to the correct diagnosis and appropriate management of patients with HP.