title: Diminished reliability of tryptase as risk indicator of mastocytosis in older overweight subjects.
abstract: BACKGROUND
  Currently, measurement of serum tryptase level is the most commonly used test to estimate the need for bone marrow biopsy in patients suspected to have indolent systemic mastocytosis (ISM). Yet tryptase levels do not solely reflect the mast cell load and can be elevated by overweight, older age, and impaired renal function. The influence of these factors on urinary methylhistamine (MH) and methylimidazole acetic acid (MIMA) is still unknown.
  
  
  OBJECTIVE
  We investigated the impact of age, body mass index (BMI), and kidney function on the diagnostic accuracy of tryptase, MH, and MIMA to select the most optimal test indicating the necessity of a bone marrow biopsy in ISM-suspected patients.
  
  
  METHODS
  Retrospective data analysis of all adults in whom bone marrow investigations were performed because of high clinical suspicion and/or elevated tryptase, MH, or MIMA.
  
  
  RESULTS
  194 subjects were included. ISM was present in 112 and absent in 82 subjects (non-ISM). Tryptase was elevated by age and body weight in non-ISM subjects and by BMI in ISM subjects; however, these factors did not influence MH or MIMA. In the total study population, the diagnostic accuracy of tryptase, MH, and MIMA were comparable (area under the curve 0.80, 0.80, and 0.83). In subjects >50 years with a BMI >25 kg/m(2), the diagnostic accuracy of MIMA was higher compared with that of tryptase (area under the curve 0.93 vs 0.74; P = .011).
  
  
  CONCLUSIONS
  In ISM-suspected patients >50 years with a BMI of >25 kg/m(2), MIMA has a greater value compared with tryptase in estimating the need for bone marrow biopsy.
authors.affiliation: Department of Allergology, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands; GRIAC Research Institute, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands.
authors.forename: Byrthe J P R
authors.initials: BJ
authors.lastname: Vos
authors.affiliation: Department of Laboratory Medicine, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands.
authors.forename: Eveline
authors.initials: E
authors.lastname: van der Veer
authors.affiliation: Department of Dermatology, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands.
authors.forename: Pieter C
authors.initials: PC
authors.lastname: van Voorst Vader
authors.affiliation: Department of Laboratory Medicine, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands.
authors.forename: André B
authors.initials: AB
authors.lastname: Mulder
authors.affiliation: Department of Laboratory Medicine, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands.
authors.forename: Sicco
authors.initials: S
authors.lastname: van der Heide
authors.affiliation: Department of Rheumatology and Clinical Immunology, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands.
authors.forename: Suzanne
authors.initials: S
authors.lastname: Arends
authors.affiliation: Department of Hematology, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands.
authors.forename: Johanna C
authors.initials: JC
authors.lastname: Kluin-Nelemans
authors.affiliation: Department of Allergology, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands; GRIAC Research Institute, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands.
authors.forename: Jan G R
authors.initials: JG
authors.lastname: de Monchy
authors.affiliation: Department of Allergology, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands.
authors.forename: Jasper J
authors.initials: JJ
authors.lastname: van Doormaal
authors.affiliation: Department of Allergology, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands; GRIAC Research Institute, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands. Electronic address: j.n.g.oude.elberink@umcg.nl.
authors.forename: Joanne N G
authors.initials: JN
authors.lastname: Oude Elberink
mesh_terms: D000328:Adult; D000367:Age Factors; D001706:Biopsy; D015992:Body Mass Index; D001853:Bone Marrow / Q000378:metabolism / Q000473:pathology; D005260:Female; D006801:Humans; D007093:Imidazoles / Q000652:urine*; D007677:Kidney Function Tests; D008407:Mast Cells / Q000378:metabolism / Q000473:pathology; D034721:Mastocytosis, Systemic / Q000175:diagnosis* / Q000473:pathology / Q000652:urine*; D008761:Methylhistamines / Q000652:urine*; D008875:Middle Aged; D012189:Retrospective Studies; D053802:Tryptases / Q000652:urine*
chemical_list: D007093:Imidazoles; D008761:Methylhistamines; C002667:methylimidazoleacetic acid; D053802:Tryptases
keywords: Age; body mass index; indolent systemic mastocytosis; mast cell; methylhistamine; methylimidazole acetic acid; tryptase