In vitro detection of Candida and Aspergillus antigen in parenteral nutrition and fixed combinations of piperacillin‐tazobactam

Summary Background Screening for Aspergillus (Asp‐AG) and Candida antigen (Ca‐AG) with immunoassays is established for stem cell recipients at high risk for invasive fungal infections (IFI). While parenteral nutrition (PN) will be applied in case of complications leading to insufficient alimentation, piperacillin‐tazobactam (TZP) is started at the onset of febrile neutropenia. Objectives The aim of this study was to investigate drug‐laboratory interactions between PN and TZP and both immunoassays which could affect the specificity of the assays and lead to the false assumption of an IFI. Methods Batches of TZP and PN were tested with both assays in vitro. In total, 380 samples of 83 batches were analysed. Results None of the examined preparations were tested positive with Asp‐AG assay. Measurable amounts of Ca‐AG were detected in a lipid emulsion, two different trace element supplements, a fat‐soluble vitamin preparation and all tested brands of TZP. Conclusions We conclude that false positivity of Asp‐AG assay due to TZP and PN does not occur. Cross reactions with Ca‐AG assay have been detected in some preparations. The in vivo relevance of Ca‐AG positivity has to be reviewed in further studies considering an effect of dilution. Physicians should be aware of a possible cross reaction with Ca‐AG assays which could lead to false‐positive results.