Hypersensitivity pneumonitis (HP) is an immunologically mediated form of lung disease resulting from inhalational exposure to a large variety of organic and, less often, nonorganic inciting antigens.1,2 The precipitin double-diffusion assay is a widely used inexpensive laboratory test for identifying candidate HP antigens. Concerns that the precipitin method is insufficiently sensitive to detect all IgG responses and that its results can sometimes be misread to give false-positives results led us to investigate whether alternative techniques, ELISA-based and ImmunoCAP-based tests,3,4 could prove to be more helpful.