title: Comparison of serum tryptase and urine N-methylhistamine in patients with suspected mastocytosis.
abstract: BACKGROUND
  The disease extent of mastocytosis can be assessed by measurement of mediators or their metabolites, secreted from mast cells. In the present study, we compared results of urinary N-methylhistamine measurements with analysis of total tryptase in serum from patients with suspected mastocytosis.
  
  
  METHODS
  Tryptase in serum was determined with the UniCAP tryptase fluor-enzyme-immunoassay, according to the manufacturers' instructions (Pharmacia, Woerden, Netherlands). N-methylhistamine in urine was determined by competitive radioimmunoassay, according to the manufacturers' instructions (Pharmacia).
  
  
  RESULTS
  A significant correlation between serum tryptase and urine N-methylhistamine was found both for 138 patients aged 14 or older (Spearman Rank r(s)=0.43, p<0.0001) and for 23 younger patients (Spearman Rank r(s)=0.46, p=0.0267). The between-run coefficient of variation of the tryptase assay was half (6.7%) of the one (13%) found with the urinary N-methylhistamine assay. Both for urine N-methylhistamine and serum tryptase, a significant difference was found between corresponding biopsies with an increased number of mast cell aggregates and biopsies without such an increase. The difference between tryptase levels however was stronger (Mann-Whitney: p=0.0012) than the difference between N-methylhistamine levels (Mann-Whitney: p=0.0140).
  
  
  CONCLUSIONS
  Serum tryptase discriminates better than urinary N-methylhistamine between patients with an increased number of mast cell aggregates and persons without such an increase.
authors.affiliation: Department of Clinical Chemistry, University Medical Center Rotterdam, Erasmus MC, Dr. Molewaterplein 40, P.O. Box 2040, 3000 CA Rotterdam, The Netherlands. a.w.vantoorenenbergen@erasmusmc.nl
authors.forename: A W
authors.initials: AW
authors.lastname: van Toorenenbergen
authors.forename: A P
authors.initials: AP
authors.lastname: Oranje
mesh_terms: D006801:Humans; D008415:Mastocytosis / Q000097:blood* / Q000652:urine*; D008761:Methylhistamines / Q000652:urine*; D015203:Reproducibility of Results; D012697:Serine Endopeptidases / Q000097:blood*; D053802:Tryptases
chemical_list: D008761:Methylhistamines; D012697:Serine Endopeptidases; D053802:Tryptases; C048140:N-methylhistamine