Skin-prick tests for hypersensitivity to alpha-amylase preparations.

Twenty-five asthmatic subjects with suspected alpha-amylase hypersensitivity were studied by skin-prick tests, a capture ELISA, immunoblotting and bronchial provocation tests. At the same time, different amylases were analysed by SDS-PAGE and immunoblotting using a polyclonal rabbit antiserum. Eight patients showed a positive bronchial response to amylase. Seven of them had positive skin-prick tests, with this method being the most sensitive approach for diagnosis. However, in four cases, skin tests were also positive although the patients had a negative provocation test, thus demonstrating that skin tests are not specific. ELISA and blotting showed similar results in terms of sensitivity and specificity. The enzymes used by the workers included several antigens besides alpha-amylase. The rabbit antiserum to alpha-amylase detected a protein in a wheat flour extract. In one case, the IgE antibodies were specific only for a contaminant of lower molecular weight than amylase. These facts suggest that proteins from the culture medium could be responsible for some cases of amylase hypersensitivity, making the diagnosis difficult. The presence of amylase in another enzymatic extract, a protease produced by Aspergillus oryzae, was proved by means of skin tests and immunoblotting, thus demonstrating the allergenic properties of this enzymatic preparation.