False positive galactomannan Platelia due to piperacillin-tazobactam

Invasive aspergillosis is a serious disease, the lethality of which is important among hematology patients. Early diagnosis is crucial for treatment options and the prognosis. Detection of the antigen galactomannan is the most frequently used microbiological tools. But galactomannan detection may be falsely positive, and this false positivity has been associated with piperacillin-tazobactam treatment, the main antibiotic combination used in clinical hematology.

The purpose of our study, carried out from January 2009 to December 2010 at the Versailles hospital on in-patients with hematological disorders, was to evaluate the association between false galactomannan positivity and administration of piperacillin-tazobactam, and to study a possible variability of products issued by three manufacturers.

We noted that 207 patients were included (n=207), accounting for 69 false positive and 138 true negative results. The intrinsic galactomannan values in the study were sensitivity 100%, specificity 68%, positive and negative predictive values respectively 16%, 100%, and a likelihood positive and negative test at respectively 3.12, and 0.

The statistical analysis did not determine any association between false positivity in galactomannan and piperacillin-tazobactam issued by two manufacturers (P=0.87 and P=0.94). But, there was a significant association between false galactomannan positivity and piperacillin-tazobactam issued by the third manufacturer (P=0.02). Four of the 25 batches issued by this manufacturer were tested and negative "in vitro" for galactomannan.

This study results suggest that the association between false galactomannan positivity and piperacillin-tazobactam is not longer systematic, but can still prevail depending on the manufacturers. It also confirmed the positive contribution of testing piperacillin-tazobactam batches "in vitro" before using the antibiotic.