Occurrence and Kinetics of False-PositiveAspergillusGalactomannan Test Results following Treatment with β-Lactam Antibiotics in Patients with Hematological Disorders

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Abstract
Several reports have described a high rate of false-positiveAspergillusgalactomannan (GM) test results for patients treated with piperacillin-tazobactam. In this retrospective study, we first examined the relationships between intravenous administration of three β-lactam antibiotics and the occurrence of false-positive GM test results in hematology patients. We then estimated the kinetics of clearance of GM after the cessation of treatment. Sequential serum samples from 69 patients that had received β-lactams were analyzed by using a PlateliaAspergillustest. A significant association was found between GM positivity (≥0.5) and the administration of β-lactams (P< 0.0001). The direct role of β-lactams in patients' serum positivity was assessed by testing 39 batches of β-lactams, of which 27 were positive for GM. None of the latter were positive according to a fungus- andAspergillus-specific PCR. The kinetics of the decrease of GM was analyzed on sequential serum samples obtained after treatment. By use of a nonlinear regression model, the average time to negative antigen was assessed to be 5.5 days (95% confidence interval [CI], 4.1 to [7.0]), with a half-life of elimination of GM of 2.4 days (95% CI, 1.8 to 3.0). This study confirms that the administration of β-lactams containing GM is responsible for false-positive diagnostic results, even up to 5 days after the cessation of treatment.

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