Enzyme-linked immunosorbent assay (ELISA) for IgG antibodies in farmers' lung disease.

The ELISA was used for detection of specific IgG antibodies to Micropolyspora faeni antigens in 158 farmers with a history of exposure to mouldy hay, eighty-eight of whom had a diagnosis of farmer's lung. The farmers' lung group had significantly higher values in the ELISA than both the seventy exposed but asymptomatic farmers (P less than 0.001) and a group of thirty-one adult controls (P less than 0.001). The asymptomatic farmers also had significantly higher values than the control group (P less than 0.02). The ELISA correlated better with the clinical diagnosis than the Ouchterlony agar-gel double-diffusion (precipitin) test. None of the control group gave positive reactions in the ELISA or the precipitin tests. The ELISA is therefore a sensitive, specific and quantitative test which is readily available and widely applicable.