Validation of an Environmental Exposure Chamber for Assessment of Allergy to Grass Pollen.

Abstract

Background: An environmental exposure chamber (EEC) is a health facility that enables allergic symptoms to be induced in a controlled manner in persons sensitized to a dispersed allergen. We performed a study at our institution to technically and clinically validate an EEC in patients allergic to grass pollen.

Methods: We developed a new EEC inside a clean room (ISO-8 class) measuring 15.6 m². During the technical validation, the patient's exposure conditions were simulated by ensuring homogeneous distribution of the allergen with a particle disperser and monitoring both particle and pollen grain concentrations. Temperature, pressure, and humidity were also registered. A total of 31 volunteers were exposed to Phleum pratense pollen in the EEC. Of these, 25 were allergic (cases), with symptoms of rhinoconjunctivitis with or without asthma, and 6 were not (controls). One control and 2 cases were exposed twice to check reproducibility, generating a total of 34 challenges. The test was stopped once the positivity criterion was reached or the patient completed 90 minutes in the EEC.

Results: Both the stability of particle concentrations and approximation to the pollen sample concentration were guaranteed. All challenges with controls were negative. Among the cases, 15% of challenges were negative and 85% were positive. No severe or late reactions were observed. Volunteers exposed twice to the same pollen had the same result in both challenges.

Conclusion: Our EEC proved to be a specific, safe, and reproducible tool for the diagnosis of grass pollen allergy.