title: False-positive results of Aspergillus galactomannan antigenemia in liver transplant recipients.
abstract: BACKGROUND
  Aspergillus galactomannan (GM) antigenemia is an early marker of invasive aspergillosis (IA), but may yield false-positive results. A prospective study, testing GM periodically in serum samples of liver transplant recipients, was performed.
  
  
  METHODS
  An index more than or equal to 0.5 were considered positive. Positive GM in samples from patients without any other criteria of proven or probable IA was considered as false-positive. The test was performed weekly during the first month after transplantation.
  
  
  RESULTS
  Three patients developed IA. In total, 414 serum samples from 85 liver transplant recipients were analyzed. Mean number of samples per patient (out of those who could be assessed) was 4.8. The number of false-positive GM samples was 40 (9.6%), corresponding to 28 patients. The frequency of false-positive results in samples obtained during the first week posttransplantation was 36% (27 of 75), significantly higher than the number of false-positive samples obtained after the first week (3.8%; 13 of 339; P<0.001). Multivariate analysis showed that antibacterial prophylaxis with ampicillin was the only independent factor associated with a false-positive result. Different vials of beta-lactam antibiotics were tested for GM. We obtained a positive GM value (>0.5) in four of the six vials of ampicillin, in three of the six vials of piperacillin-tazobactam, in none of the six vials of cefotaxime, and in none of the six controls.
  
  
  CONCLUSIONS
  The present study suggests that the administration of ampicillin as antibacterial prophylaxis during the first days after transplantation could be a possible cause of false-positive GM results.
authors.affiliation: Department of Infectious Diseases, Hospital Ramón y Cajal, Madrid, Spain. fortunabete@gmail.com
authors.forename: Jesus
authors.initials: J
authors.lastname: Fortún
authors.forename: Pilar
authors.initials: P
authors.lastname: Martín-Dávila
authors.forename: Maria E
authors.initials: ME
authors.lastname: Alvarez
authors.forename: Francesca
authors.initials: F
authors.lastname: Norman
authors.forename: Aurora
authors.initials: A
authors.lastname: Sánchez-Sousa
authors.forename: Luis
authors.initials: L
authors.lastname: Gajate
authors.forename: Rafael
authors.initials: R
authors.lastname: Bárcena
authors.forename: S Javier
authors.initials: SJ
authors.lastname: Nuño
authors.forename: Santiago
authors.initials: S
authors.lastname: Moreno
mesh_terms: D000667:Ampicillin / Q000737:chemistry; D000900:Anti-Bacterial Agents / Q000737:chemistry; D000946:Antigens, Fungal / Q000097:blood*; D001228:Aspergillosis / Q000175:diagnosis* / Q000209:etiology / Q000276:immunology; D001230:Aspergillus / Q000276:immunology*; D004340:Drug Contamination; D004797:Enzyme-Linked Immunosorbent Assay; D005189:False Positive Reactions; D005690:Galactose / Q000031:analogs & derivatives; D006801:Humans; D016031:Liver Transplantation / Q000009:adverse effects*; D008351:Mannans / Q000032:analysis / Q000097:blood*; D011237:Predictive Value of Tests; D011446:Prospective Studies; D013997:Time Factors
chemical_list: D000900:Anti-Bacterial Agents; D000946:Antigens, Fungal; D008351:Mannans; C012990:galactomannan; D000667:Ampicillin; D005690:Galactose