Prospective sandwich enzyme-linked immunosorbent assay for serum galactomannan: early predictive value and clinical use in invasive aspergillosis

Serial monitoring of Aspergillus antigen in the early diagnosis of invasive aspergillosis. Preliminary investigations with two examples

A recently developed sandwich ELISA, which detects Aspergillus galactomannan, was tested retrospectively in serial serum samples from an allogeneic bone marrow transplant recipient with proven invasive aspergillosis (patient 1) and another with suspected disease (patient 2). Galactomannan was detected in the serum 4 and 28 days, respectively, before pulmonary infiltrates suggestive of fungal infection first became apparent on the chest X-ray. Aspergillus was detected by ELISA and PCR in BAL fluid samples from both patients, and in CSF from patient 1. The diagnosis was confirmed at autopsy for patient 1 by histopathology and the recovery of Aspergillus fumigatus from the lung and brain. Furthermore, in both patients the course of the antigen titer in the serum during antifungal treatment corresponded with the clinical outcome. These results confirm that the sandwich ELISA appears to be useful for the early diagnosis of invasive aspergillosis. The value of the test for monitoring the response to antifungal treatment remains to be established in prospective trials.

Specificity of a sandwich enzyme-linked immunosorbent assay for detecting Aspergillus galactomannan

The specificity of a sandwich enzyme-linked immunosorbent assay (ELISA) for detecting Aspergillus galactomannan was tested with exoantigens of 29 fungi cultured from clinical specimens. Cross-reactivity was observed with Penicillium chrysogenum, Penicillium digitatum, and Paecilomyces variotii. Furthermore, 40 serum samples obtained from bacteremic patients with hematologic malignancies were retrospectively tested by sandwich ELISA. False-positive reactions with the serum were reproducible but did not correspond with the results of culture of specific microorganisms. Moreover, the microorganisms cultured from the blood showed no reactivity by the sandwich ELISA.