title: Comparison of different local and imported histamine concentrations used as a skin prick test positive control.
abstract: BACKGROUND
  The skin prick test (SPT) is a valid and approved tool that is used to diagnose atopic diseases. The SPT is accurate, safe, simple and inexpensive. However, the histamine concentration used as a positive control in the SPT varies among centers.
  
  
  OBJECTIVE
  To compare SPT results using different concentrations of locally-prepared and imported histamine solutions.
  
  
  METHODS
  This prospective, randomized, double-blind, self-controlled study was performed in healthy adult volunteers. The SPT was performed using 4 concentrations of histamine solutions (imported, 1 mg/mL; locally-prepared, 1, 5 and 10 mg/mL). Locally-prepared histamine positive controls were prepared from histamine biphosphate monohydrate using sterile technique.
  
  
  RESULTS
  Seventy-five adult volunteers (mean age, 36 years) were included in the study. Eight volunteers were male and 9 had a history of atopy. Mean wheal diameter (MWD) for imported histamine was 3.49 mm for a concentration of 1 mg/mL, and that of locally-prepared histamine was 2.94 mm, 5.05 mm and 5.52 mm for concentrations of 1, 5 and 10 mg/mL histamine, respectively. Negative SPT results (MWD <3 mm) were found in 11 subjects (14.7%) who received imported histamine and 26 subjects (34.7%) who received the locally-prepared histamine at concentration of 1 mg/mL. All subjects tested with locally-prepared histamine at concentrations of 5 and 10 mg/mL had a MWD > 3 mm.
  
  
  CONCLUSIONS
  Locally-prepared histamine base at concentrations of 5 and 10 mg/mL yielded better positive results than both imported and locally-prepared histamine at a concentration of 1 mg/mL.
authors.affiliation: Division of Allergy and Immunology, Department of Pediatrics, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok 10700, Thailand.
authors.forename: Nualanong
authors.initials: N
authors.lastname: Visitsunthorn
authors.affiliation: Division of Allergy and Immunology, Department of Pediatrics, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok 10700, Thailand.
authors.forename: Kittipos
authors.initials: K
authors.lastname: Visitsunthorn
authors.affiliation: Division of Allergy and Immunology, Department of Pediatrics, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok 10700, Thailand.
authors.forename: Sunisa
authors.initials: S
authors.lastname: Aulla
authors.affiliation: Department of Otorhinolaryngology, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok 10700, Thailand.
authors.forename: Chaweewan
authors.initials: C
authors.lastname: Bunnag
authors.affiliation: Division of Allergy and Immunology, Department of Pediatrics, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok 10700, Thailand.
authors.forename: Orathai
authors.initials: O
authors.lastname: Jirapongsananuruk
mesh_terms: D000328:Adult; D004305:Dose-Response Relationship, Drug; D004311:Double-Blind Method; D005260:Female; D006632:Histamine / Q000008:administration & dosage / Q000031:analogs & derivatives*; D017442:Histamine Agonists / Q000008:administration & dosage*; D006801:Humans; D006969:Hypersensitivity, Immediate / Q000175:diagnosis*; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012882:Skin Tests / Q000379:methods*
chemical_list: D017442:Histamine Agonists; D006632:Histamine; C027556:histamine phosphate