title: Macroprolactin, big-prolactin and potential effects on the misdiagnosis of hyperprolactinemia using the Beckman Coulter Access Prolactin assay.
abstract: OBJECTIVE
  To examine whether use of the Beckman Coulter Access Prolactin (PRL) assay, which has low reactivity with macro-PRL, obviates the need for screening hyperprolactinemic samples.
  
  
  METHODS
  Samples from 1020 hyperprolactinemic individuals and 401 healthy volunteers were treated with polyethylene glycol (PEG). Macro-PRL was assessed from (1) percent PRL recovery, using cut-off values derived by gel filtration chromatography (GFC) and (2) significant (p<0.05) normalisation of PRL following PEG.
  
  
  RESULTS
  PRL recovery was similar in volunteer and hyperprolactinemic samples (mean+/-SD 101+/-13% and 101+/-19%, respectively). In hyperprolactinemic samples, macro-PRL was identified from PRL recovery in 9.7%, although levels were moderate to high in only 3.9%. The total PRL normalised following PEG in 7.4%. Correlations of PRL recovery with the proportions of macro-, big- and monomeric PRL following GFC (n=30 samples, range of PRL and macro-PRL levels) were -0.89, -0.20 and 0.92, respectively. The big-PRL content was 0-28%. Regression analysis suggested that PEG precipitated both macro-PRL and big-PRL.
  
  
  CONCLUSIONS
  Using the Access assay, macro-PRL can cause apparent hyperprolactinemia and big-PRL may cause misclassification of individuals. Screening using PEG is applicable to assays with low macro-PRL reactivity provided specific reference values are derived.
authors.affiliation: Endolab, Christchurch Hospital, Private Bag 4710, Christchurch, New Zealand. Jane.ellis@cdhb.govt.nz
authors.forename: M Jane
authors.initials: MJ
authors.lastname: Ellis
authors.forename: John H
authors.initials: JH
authors.lastname: Livesey
authors.forename: Steven G
authors.initials: SG
authors.lastname: Soule
mesh_terms: D002850:Chromatography, Gel; D003951:Diagnostic Errors; D004864:Equipment and Supplies; D006801:Humans; D006966:Hyperprolactinemia / Q000175:diagnosis*; D011388:Prolactin / Q000097:blood*
chemical_list: C060678:prolactin, polymeric; D011388:Prolactin