Antibody to Aspergillus fumigatus antigens in normal sera: influence on positive-negative discrimination in ELISA.

The response of precipitin-negative sera from non-selected asthmatic patients against a range of somatic and culture filtrate antigens of Aspergillus fumigatus in ELISA for anti-A. fumigatus IgG is described. Antibody to the various antigens was widely distributed but the precise distribution was dependent upon antigen type. To determine how the selection of negative reference sera from precipitin-negative sera can influence the discrimination between precipitin-positive and -negative sera in ELISA, panels of 10 sera were chosen from the extremes of the frequency distribution and by random selection. The closest agreement between precipitin testing and ELISA was seen when randomly-selected negative reference sera were incorporated in the assay, although the degree of correlation was dependent upon the detector antigen. These findings demonstrate the requirement for careful selection of sera included as negative reference sera in ELISA for anti-A. fumigatus IgG.