title: A practical method for the detection of macroprolactinaemia using ultrafiltration.
abstract: OBJECTIVE
  The aim of this study was to evaluate a method for the estimation of the percentage of big-big prolactin (bb-PRL) in serum, based on centrifugal ultrafiltration (UF) and to be used for the detection of macroprolactinaemia.
  
  
  METHODS
  Serum samples were submitted to gel filtration chromatography (GFC), UF and precipitation with polyethylene glycol (PEG).
  
  
  METHODS
  Serum samples obtained from 13 patients with macroprolactinaemia (Group 1) and from 15 hyperprolactinaemic patients without macroprolactinaemia (Group 2) were studied by the three methods.
  
  
  METHODS
  PRL was measured in serum, fractions from GFC, filtrate and retentate obtained after UF (this last measurement was used only to study the 'recovery' of PRL after UF and was not necessary for clinical purposes), and supernatant obtained after PEG precipitation. The calculation of the percentage of bb-PRL, by UF, was made using a simple algorithm.
  
  
  RESULTS
  In Group 1 the percentages (mean and SD) of bb-PRL as determined by GFC, UF and PEG were, respectively, 73 +/- 16, 83 +/- 5.3 and 78 +/- 7.0. In Group 2, the percentages of bb-PRL were, in the same order as above, 4.3 +/- 8.2, 16 +/- 19 and 3.7 +/- 11. The difference of the means between Groups 1 and 2 was highly significant (P << 0.001) for all the three methods. In Group 1 the percentages of bb-PRL were widely scattered when measured by GFC but closely clustered when measured by either UF or PEG. The opposite occurred in Group 2.
  
  
  CONCLUSIONS
  The centrifugal ultrafiltration method for the detection of macroprolactinaemia is simple, inexpensive, requires only two prolactin assays and yields the same results as the polyethylene glycol precipitation method.
authors.affiliation: Department of Endocrinology and Laboratory of Endocrinology, Portuguese Institute of Oncology, Lisbon, Portugal.
authors.forename: Susana
authors.initials: S
authors.lastname: Prazeres
authors.forename: M Amparo
authors.initials: MA
authors.lastname: Santos
authors.forename: H Gil
authors.initials: HG
authors.lastname: Ferreira
authors.forename: Luís G
authors.initials: LG
authors.lastname: Sobrinho
mesh_terms: D000236:Adenoma / Q000097:blood; D015415:Biomarkers / Q000097:blood; D002850:Chromatography, Gel; D005260:Female; D006177:Gynecomastia / Q000097:blood; D006440:Hemofiltration / Q000379:methods; D006801:Humans; D006966:Hyperprolactinemia / Q000097:blood*; D015592:Immunoradiometric Assay; D008297:Male; D010911:Pituitary Neoplasms / Q000097:blood; D011388:Prolactin / Q000097:blood*; D012680:Sensitivity and Specificity
chemical_list: D015415:Biomarkers; C060678:prolactin, polymeric; D011388:Prolactin