Serological tests in the diagnosis of pulmonary aspergillosis

Sera from 44 patients with clinically suspected pulmonary aspergillosis (mainly of an allergic type) were examined for antibodies to Aspergillus fumigatus using an enzyme-linked immunosorbent assay (ELISA) and counter-immunoelectrophoresis (CIE). Of the sera, 15 were considered to contain Aspergillus antibodies using ELISA; 11 of these also contained precipitins by CIE. In no instance was a CIE-positive serum negative by ELISA. The serum of 1 patient with autopsy-verified invasive pulmonary aspergillosis was negative in both tests. Protein-enriched antigens derived by ammonium sulphate precipitation of crude hyphal homogenates seemed of most use in ELISAs. In addition, 4 of 8 sera obtained from patients with possibly invasive candidosis also revealed significant levels of Aspergillus antibody by ELISA (but not CIE). All of the 8 sera contained readily detectable Candida precipitins by CIE. Problems of potential cross-reactivity obviously need careful consideration with ELISAs. Our results suggest that ELISA procedures under appropriately controlled conditions are more sensitive than CIE for detecting Aspergillus antibodies. However it seems that some patients with invasive aspergillosis will be antibody-negative even with sensitive tests such as ELISA.