title: The importance of glycerin-containing negative control tests in allergy research studies that use intradermal skin tests.
abstract: OBJECTIVE
  We sought to assess skin whealing with glycerin-containing control injections for intradermal skin tests.
  
  
  METHODS
  Observational.
  
  
  METHODS
  Wheal sizes were measured at 0, 10, and 15 minutes after intradermal injection of 0.01 and 0.02 mL of phenolated normal saline and 0.5% and 5% concentrations of glycerin in the same quantity of phenolated saline.
  
  
  RESULTS
  Intradermal injection of 0.01 mL of phenolated saline produced an average 4.9-mm wheal, which expanded to 5.2 mm at 10 minutes and to 6.0 mm at 15 minutes. Intradermal injection of 0.02 mL of phenolated saline produced a 6.4-mm wheal, which expanded to 7.0 mm at 10 minutes and 8.0 mm at 15 minutes. The addition of glycerin produced proportionally larger wheals.
  
  
  CONCLUSIONS
  Because glycerin increases whealing beyond that with phenolated saline, skin tests containing glycerin must be compared with glycerin-containing negative controls. Intradermal skin tests that fail to compare findings in this manner contain an inherent methodologic flaw and are uninterpretable.
authors.affiliation: Tufts University, Boston, Massachusetts, USA.
authors.forename: David S
authors.initials: DS
authors.lastname: Hurst
authors.forename: Bruce R
authors.initials: BR
authors.lastname: Gordon
authors.forename: John H
authors.initials: JH
authors.lastname: Krouse
mesh_terms: D015982:Bias; D005188:False Negative Reactions; D005189:False Positive Reactions; D005990:Glycerol / Q000008:administration & dosage*; D017408:Guidelines as Topic; D006801:Humans; D006967:Hypersensitivity / Q000175:diagnosis*; D007271:Injections, Intradermal; D011446:Prospective Studies; D012680:Sensitivity and Specificity; D012882:Skin Tests / Q000379:methods* / Q000592:standards*; D012965:Sodium Chloride / Q000008:administration & dosage; D013997:Time Factors
chemical_list: D012965:Sodium Chloride; D005990:Glycerol