Tests are performed with standardized antigens of A. flavus, A. niger and A. fumigatus. Positive results, represented by one or more precipitin lines, are indicative of fungus ball, allergic bronchopulmonary aspergillosis (ABA), or invasive aspergillosis. Generally, the finding of 3-4 bands will indicate either fungus ball or ABA, with many cases of invasive aspergillosis requiring serum concentration for demonstration of precipitin lines.