Comparison ofAspergillusgalactomannan antigen testing with a new cut-off index andAspergillusprecipitating antibody testing for the diagnosis of chronic pulmonary aspergillosis

Background and objective: The usefulness of two tests in the serodiagnosis of chronic pulmonary aspergillosis (CPA) was compared. The tests were the serum Aspergillus galactomannan antigen test (Platelia (R) Aspergillus) by enzyme-linked immunoassay (EIA) using old and new cut-off indexes, and the Aspergillus precipitating antibody test. Methods: Both Aspergillus-precipitating antibody and Platelia Aspergillus EIA positivity were measured in the sera of 28 patients at the time of diagnosis of CPA. Results: Serum Aspergillus precipitating antibody positivity was 89.3% (25/28) in CPA patients. Serum Platelia Aspergillus EIA positivity was 21.4% (6/28) using the old cut-off index (≥1.5) and 50% (14/28) using the new cut-off index (≥0.5)—still less than that for Aspergillus precipitating antibody. Three of the 28 CPA patients had positive reactions in the Platelia Aspergillus EIA using the old cut-off index but not in the Aspergillus precipitating antibody test. Positivity for (1,3) β-d glucan was 15.4%, and that for culture on CHROMagar Candida was 17.9%. One patient with pulmonary actinomycosis had a false-positive reaction in the Platelia Aspergillus test with the new cut-off index. Conclusions: For the diagnosis of CPA, Aspergillus precipitating antibody testing is more sensitive than the Platelia Aspergillus EIA, even with the new cut-off index. False-positive reactions are observed with the Platelia Aspergillus EIA in patients with conditions such as pulmonary actinomycosis. Results should be interpreted with care when patients are positive for the Platelia Aspergillus EIA but negative for Aspergillus precipitating antibody.