False-positive serum and bronchoalveolar lavage Aspergillus galactomannan assays caused by different antibiotics

Abstract

Our objective was to identify false-positive serum and bronchoalveolar lavage (BAL) fluid galactomannan (GM) tests caused by various antibiotics commonly used in general practice. Serum and BAL samples from patients who did not have the diagnostic criteria of invasive aspergillosis and received different antibiotics were prospectively analyzed for GM. Serum and BAL samples were also collected from patients who did not receive antibiotics. At the cut-off index of ≥0.5, false-positive serum results were found in patients who received amoxicillin–clavulanate, piperacillin–tazobactam, cefepime, and cefoperazone–sulbactam (26.7%, 58.3%, 14.3%, and 66.7%, respectively). Fungal colonization in BAL samples had a higher BAL GM than those without fungal colonization. In 71 patients who had a negative BAL culture for fungi, at the cut-off value of ≥1.0, false-positive BAL fluid results were found in patients who received amoxicillin–clavulanate (27.3%), piperacillin–tazobactam (50%), cefepime (16.7%), carbapenem (45.5%), and ceftriaxone (45.5%). False-positive serum and BAL GM assays were also detected in patients who did not receive any antibiotics. In summary, this study demonstrates the false-positive GM levels in serum and BAL caused by β-lactam antibiotics that are commonly used in general practice. Physicians should be aware of this possible interference.

Acknowledgements

The authors thank Dr Amnuay Thithapandha for constructive suggestions and English editing.

Declaration of interest: All of us declare that we do not have a conflict of interest and that we do not have a financial relationship with a commercial entity that has an interest in the subject of this manuscript.