title: Macroamylase detection in serum using selective precipitation: a rapid and reliable assay.
abstract: OBJECTIVE
  Available assays for measurement of pancreatic isoamylase in serum based on specific immunoinhibition of salivary fraction are unable to detect macroamylase. We combined a polyethylene glycol test which identifies macroamylase by selective precipitation with an automated assay for total amylase and pancreatic isoamylase measurement.
  
  
  METHODS
  We analysed 24 sera proven positive for macroamylase using gel filtration chromatography and 80 negative sera. Precipitation of macroamylase with polyethylene glycol, colourimetric measurement of total amylase activity and immunoinhibition for the determination of pancreatic isoamylase were carried out.
  
  
  RESULTS
  Macroamylasaemic sera showed precipitation of at least 71% of the amylase activity, while sera with normal-sized amylase exhibited a maximum of 61%. In all the macroamylasaemic sera but two, the immunoinhibition test showed a rise in pancreatic isoamylase, which was found to be the prevalent fraction in 16. In 21 out of 24 sera with macroamylase and 67 out of 80 with normal-sized amylase, the precipitated amylase activity was also measured after immunoinhibition of non pancreatic activity. In macroamylasaemic sera, the percentage of precipitated pancreatic isoamylase activity ranged from 75% to 98%, while in samples with normal-sized amylase it was less than 71%.
  
  
  CONCLUSIONS
  Polyethylene glycol precipitation can easily be combined with automated assays for the determination of pancreatic isoamylase and should be carried out whenever dealing with hyperamylasaemia of unclear origin.
authors.affiliation: Department of Internal Medicine and Gastroenterology, University of Bologna, Italy. Ventrucc@med.unibo.it
authors.forename: M
authors.initials: M
authors.lastname: Ventrucci
authors.forename: A
authors.initials: A
authors.lastname: Cipolla
authors.forename: M
authors.initials: M
authors.lastname: Middonno
authors.forename: C
authors.initials: C
authors.lastname: Racchini
authors.forename: E
authors.initials: E
authors.lastname: Pollini
authors.forename: G V
authors.initials: GV
authors.lastname: Melzi d'Eril
mesh_terms: D000681:Amylases / Q000097:blood*; D011232:Chemical Precipitation; D006801:Humans; D046911:Macromolecular Substances; D011092:Polyethylene Glycols; D015203:Reproducibility of Results; D012997:Solvents; D013997:Time Factors
chemical_list: D046911:Macromolecular Substances; D012997:Solvents; D011092:Polyethylene Glycols; D000681:Amylases; C001663:macroamylase