Significance and interpretation of laboratory tests in pulmonary aspergillosis.

The significance of the isolation of Aspergillus fumigatus from sputum may be difficult to interpret because of the frequent occurrence of this fungus in the atmosphere. Criteria are given for classifying positive sputa into two groups, ;fungus scanty' and ;fungus abundant', on the basis of cultural and microscopical findings. A relationship between sputum findings thus classified and the occurrence of Aspergillus antibodies in the patient's serum is demonstrated. The diagnostic importance of direct microscopical examination of sputum is noted. The precipitation patterns of sera to the unstandardized antigenic extracts of A. fumigatus at present available vary greatly. An arbitrary but practical classification of sera is suggested, based on the ;reactivity', or number of precipitation lines produced, and the ;range', or number of antigenic extracts with which the serum reacts.