title: Free prolactin determinations in hyperprolactinemic men with suspicion of macroprolactinemia.
abstract: BACKGROUND
  The Elecsys prolactin (PRL) assay reacts more strongly with macroprolactin than the Centaur PRL assay. We evaluated Elecsys direct and free PRL measurements vs. Centaur direct PRL measurements, in sera with and without macroprolactin.
  
  
  METHODS
  PRL was measured using Elecsys and Centaur direct assays and the Elecsys assay in the supernatant obtained after PEG precipitation (free PRL) in 34 sera from 34 hyperprolactinemic male subjects (Elecsys direct PRL>434 mIU/l) classified, according to the PRL recovery after PEG precipitation, as: negative, i.e. without predominant macroprolactin (recovery %>50, n=12), positive (recovery %<40, n=18) or indeterminate (n=4).
  
  
  RESULTS
  The positive bias between Elecsys direct and Centaur PRL results was clearly influenced by the presence of macroprolactin and the mean bias between Elecsys free and Centaur prolactin values was near zero in the negative and positive groups. Among 14 patients from the positive group presenting clinical conditions possibly ascribable to hyperprolactinemia, Elecsys free and Centaur PRL levels were normal in seven and increased in five. In the negative and positive groups considered together, Elecsys free PRL agreed well with Centaur prolactin (28/30). The poor concordance observed for the indeterminate samples underlined the heterogeneity of macroprolactin.
  
  
  CONCLUSIONS
  Elecsys free PRL determination can be used to reduce the marked influence of macroprolactin in this assay.
authors.affiliation: Laboratoire Universitaire de Biophysique, Unité d'Analyses Endocriniennes, CNRS UPRES-A7004, Faculté de Médecine, Université Louis Pasteur, 67085 Strasbourg Cedex, France. sapin@ipb.u-strasbg.fr
authors.forename: Rémy
authors.initials: R
authors.lastname: Sapin
authors.forename: Françoise
authors.initials: F
authors.lastname: Gasser
authors.forename: Daniel
authors.initials: D
authors.lastname: Grucker
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D011232:Chemical Precipitation; D002648:Child; D019963:Clinical Chemistry Tests / Q000379:methods / Q000592:standards; D019281:Dimerization; D006801:Humans; D006966:Hyperprolactinemia / Q000097:blood*; D046911:Macromolecular Substances; D008297:Male; D008875:Middle Aged; D011092:Polyethylene Glycols; D011388:Prolactin / Q000097:blood*; D011933:Reagent Kits, Diagnostic / Q000592:standards*
chemical_list: D046911:Macromolecular Substances; D011933:Reagent Kits, Diagnostic; C060678:prolactin, polymeric; D011092:Polyethylene Glycols; D011388:Prolactin