title: Piperacillin/tazobactam (Tazocin™) seems to be no longer responsible for false-positive results of the galactomannan assay.
abstract: OBJECTIVE
  Galactomannan (GM) testing is extremely useful for diagnosing invasive aspergillosis in high-risk patients, but false-positive results have been reported in patients treated with piperacillin/tazobactam. The aims of this study are to test if the recent piperacillin/tazobactam (Tazocin™; Pfizer) preparation still contains GM, and if serum GM positivity in haematopoietic stem cell transplant (HSCT) recipients receiving piperacillin/tazobactam can be attributed to this treatment.
  
  
  METHODS
  Serum samples obtained from 1 October 2009 to 31 October 2010 from HSCT recipients for GM testing were analysed. The difference in the rate of positive results (defined as GM ≥ 0.5) in patients receiving and not receiving piperacillin/tazobactam was evaluated. Piperacillin/tazobactam vials from randomly selected batches were tested.
  
  
  RESULTS
  Of 1606 samples drawn in the absence of piperacillin/tazobactam therapy, 25 (1.6%) tested positive for GM versus 10 of 394 samples (2.5%) drawn while on piperacillin/tazobactam (P = 0.18). The median GM result of samples drawn on piperacillin/tazobactam was slightly higher than that of samples drawn in the absence of piperacillin/tazobactam (0.141 versus 0.122; P < 0.001). All 90 piperacillin/tazobactam vials from 30 randomly selected batches tested negative for GM, with a median GM value of 0.057 (range: 0.011-0.320).
  
  
  CONCLUSIONS
  Although some residual GM might still be present in piperacillin/tazobactam, currently available brand piperacillin/tazobactam preparations seem no longer responsible for false-positive GM results.
authors.affiliation: Division of Infectious Diseases, San Martino University Hospital and University of Genoa, Genoa, Italy. m.mikulska@unige.it
authors.forename: M
authors.initials: M
authors.lastname: Mikulska
authors.forename: E
authors.initials: E
authors.lastname: Furfaro
authors.forename: V
authors.initials: V
authors.lastname: Del Bono
authors.forename: A M
authors.initials: AM
authors.lastname: Raiola
authors.forename: S
authors.initials: S
authors.lastname: Ratto
authors.forename: A
authors.initials: A
authors.lastname: Bacigalupo
authors.forename: C
authors.initials: C
authors.lastname: Viscoli
mesh_terms: D000900:Anti-Bacterial Agents / Q000008:administration & dosage* / Q000737:chemistry; D001228:Aspergillosis / Q000175:diagnosis*; D005189:False Positive Reactions; D005690:Galactose / Q000031:analogs & derivatives; D018380:Hematopoietic Stem Cell Transplantation; D006801:Humans; D008351:Mannans / Q000097:blood*; D010397:Penicillanic Acid / Q000008:administration & dosage / Q000031:analogs & derivatives / Q000737:chemistry; D010878:Piperacillin / Q000008:administration & dosage / Q000737:chemistry; D000077725:Piperacillin, Tazobactam Drug Combination
chemical_list: D000900:Anti-Bacterial Agents; D008351:Mannans; C012990:galactomannan; D000077725:Piperacillin, Tazobactam Drug Combination; D010397:Penicillanic Acid; D010878:Piperacillin; D005690:Galactose