title: Concentrations and stability of methyl methacrylate, glutaraldehyde, formaldehyde and nickel sulfate in commercial patch test allergen preparations.
abstract: BACKGROUND
  Epicutaneous patch tests are used to reproduce allergy and diagnose allergic contact dermatitis. Reliable allergen test preparations are required.
  
  
  OBJECTIVE
  The purpose of the present study was to measure the actual concentrations of nickel(II) sulfate hexahydrate (NiSO4 ), methyl methacrylate, formaldehyde, and glutaraldehyde, and to compare them with the labelled concentrations, in commercial patch test allergen preparations found in dermatology clinics where patch testing is routinely performed.
  
  
  METHODS
  The commercial in-date and out-of-date patch test allergen preparations concentrations of NiSO4 , methyl methacrylate, formaldehyde and glutaraldehyde from one to three participating clinics were analysed with chromatographic or wet chemical techniques.
  
  
  RESULTS
  NiSO4 and formaldehyde concentrations were at or above the labelled concentrations; however, formaldehyde loss occurred with storage. NiSO4 particulate was uniformly distributed throughout the petrolatum. 'In-use' methyl methacrylate reagent syringes all contained ≤ 56% of the 2% label concentration, with no observable relationship with expiration date. Lower methyl methacrylate cocentrations were consistently measured at the syringe tip end, suggesting loss resulting from methyl methacrylate's volatility. The concentrations of glutaraldehyde patch test allergen preparations ranged from 27% to 45% of the labelled (1% in pet.) concentration, independently of expiration date.
  
  
  CONCLUSIONS
  Some false-negative methyl methacrylate, formaldehyde or glutaraldehyde patch test results may be attributable to instability of the test preparations.
authors.affiliation: Health Effects Laboratory Division, Allergy and Clinical Immunology Branch, National Institute for Occupational Safety and Health (NIOSH), Morgantown, WV 26505, USA.
authors.forename: Paul D
authors.initials: PD
authors.lastname: Siegel
authors.forename: Joseph F
authors.initials: JF
authors.lastname: Fowler
authors.forename: Brandon F
authors.initials: BF
authors.lastname: Law
authors.forename: Erin M
authors.initials: EM
authors.lastname: Warshaw
authors.forename: James S
authors.initials: JS
authors.lastname: Taylor
mesh_terms: D000485:Allergens / Q000032:analysis* / Q000737:chemistry; D017449:Dermatitis, Allergic Contact / Q000175:diagnosis; D004355:Drug Stability; D005557:Formaldehyde / Q000032:analysis* / Q000737:chemistry; D005976:Glutaral / Q000032:analysis* / Q000737:chemistry; D006801:Humans; D020366:Methylmethacrylate / Q000032:analysis* / Q000737:chemistry; D009532:Nickel / Q000032:analysis* / Q000737:chemistry; D010328:Patch Tests / Q000379:methods*
chemical_list: D000485:Allergens; D020366:Methylmethacrylate; D005557:Formaldehyde; C029938:nickel sulfate; D009532:Nickel; D005976:Glutaral
keywords: concentration and stability; formaldehyde; glutaraldehyde; methyl methacrylate; nickel sulfate; patch test allergens
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