title: Importance of operational factors in the reproducibility of Aspergillus galactomannan enzyme immune assay.
abstract: BACKGROUND
  The Platelia Aspergillus Ag assay (Bio-Rad) is designed for detecting Aspergillus galactomannan (GM) and is widely used for diagnosing invasive aspergillosis but is hampered by variable occurrences of unreproducible positive results. Frequency and origin of these unreproducible results have not been formally studied.
  
  
  METHODS
  Different technicians simultaneously performed four tests on 550 consecutive sera from adult patients (Test#1-Test#2 for extraction#1 and Test#3-Test#4 for extraction#2). The samples were classified as confirmed negative [all tests with GM optical density index (GM-ODI) <0.5], confirmed positive (all tests with GM-ODI ≥0.5), extraction unreproducible positive (Test#1 and Test#2 ODIs ≥0.5, and Test#3 and Test#4 GM-ODIs <0.5, or conversely), and ELISA unreproducible positive (only one test with GM-ODI ≥0.5). The samples with positive and negative GM-ODIs within the assay coefficient of variation values were classified as non-conclusive. Four similar additional tests were performed after ≤72h storage at 4 °C and a new GM test after 8 months at -20 °C.
  
  
  RESULTS
  Five-hundred-twenty sera (94.5%) were confirmed negative, 15 (2.7%) confirmed positive, 4 (0.7%) extraction unreproducible positive, 6 (1.1%) ELISA unreproducible positive, and 5 (0.9%) non-conclusive. Upon retesting, the unreproducible positive results turned negative except for one which turned non-conclusive. The confirmed positive and non-conclusive had similar GM-ODIs (p>0.4) upon retesting after storage ≤72h at 4 °C (n = 20) or eight months at -20 °C (n = 17).
  
  
  CONCLUSIONS
  Operational unreproducible positives represent 33% of the GM-positive results and a second sample evaluation appears mandatory to avoid useless investigations or treatments. When operational artifacts are excluded, GM remains stable at standard storage conditions.
authors: Laboratoire de Parasitologie-Mycologie, Groupe hospitalier Lariboisière-Saint Louis, Assistance Publique-Hôpitaux de Paris (APHP), Paris, France; Université Paris Diderot, Sorbonne Paris Cité, Paris, France.
authors: Nicolas
authors: N
authors: Guigue
authors: Bio-Rad Laboratories, Steenvoorde, France.
authors: Samuel
authors: S
authors: Lardeux
authors: Laboratoire de Parasitologie-Mycologie, Groupe hospitalier Lariboisière-Saint Louis, Assistance Publique-Hôpitaux de Paris (APHP), Paris, France; Université Paris Diderot, Sorbonne Paris Cité, Paris, France; CNRS URA3012, Paris, France; Institut Pasteur, Unité de Mycologie Moléculaire, Centre National de Référence Mycoses Invasives et Antifongiques, Paris, France.
authors: Alexandre
authors: A
authors: Alanio
authors: Laboratoire de Parasitologie-Mycologie, Groupe hospitalier Lariboisière-Saint Louis, Assistance Publique-Hôpitaux de Paris (APHP), Paris, France.
authors: Samia
authors: S
authors: Hamane
authors: Bio-Rad Laboratories, Steenvoorde, France.
authors: Marc
authors: M
authors: Tabouret
authors: Laboratoire de Parasitologie-Mycologie, Groupe hospitalier Lariboisière-Saint Louis, Assistance Publique-Hôpitaux de Paris (APHP), Paris, France; Université Paris Diderot, Sorbonne Paris Cité, Paris, France; CNRS URA3012, Paris, France; Institut Pasteur, Unité de Mycologie Moléculaire, Centre National de Référence Mycoses Invasives et Antifongiques, Paris, France.
authors: Stéphane
authors: S
authors: Bretagne
mesh_terms: D000328:Adult; D000946:Antigens, Fungal / Q000097:blood; D001228:Aspergillosis / Q000175:diagnosis* / Q000382:microbiology; D001230:Aspergillus / Q000737:chemistry* / Q000276:immunology; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods; D005189:False Positive Reactions; D005690:Galactose / Q000031:analogs & derivatives; D006801:Humans; D008351:Mannans / Q000097:blood* / Q000276:immunology; D015203:Reproducibility of Results
chemical_list: D000946:Antigens, Fungal; D008351:Mannans; C012990:galactomannan; D005690:Galactose