Design issues in studies evaluating diagnostic tests for aspergillosis.

Although invasive aspergillosis is recognized as an increased concern for immunosuppressed patients, establishing an early diagnosis remains a challenge. Current methods for diagnosis, including sensitive radiography and invasive procedures to identify organisms in affected tissues, provide an early diagnosis for only a small proportion of patients infected with Aspergillus species. The availability of a standardized assay to detect circulating Aspergillus galactomannan, the BioRad Platelia Aspergillus galactomannan enzyme immunoassay, should be considered as a valuable tool. However, at present, clinical utility is hampered by controversies surrounding the performance of the test and an apparent lack of definitive data. These controversies emphasize the complexity inherent in analyzing diagnostic tests for aspergillosis. The widespread availability of a standardized assay may now allow us to address the multiple sources of variability and bias via large, cooperative studies.