Comparison of serum tryptase and urine N-methylhistamine in patients with suspected mastocytosis.
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.
van Toorenenbergen
A W
AW
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
Oranje
A P
AP
D006801:Humans; D008415:Mastocytosis / Q000097:blood* / Q000652:urine*; D008761:Methylhistamines / Q000652:urine*; D015203:Reproducibility of Results; D012697:Serine Endopeptidases / Q000097:blood*; D053802:Tryptases
D008761:Methylhistamines; D012697:Serine Endopeptidases; D053802:Tryptases; C048140:N-methylhistamine