title: Specific IgE to isocyanates: a useful diagnostic role in occupational asthma.
abstract: BACKGROUND
  Isocyanates are the most frequent cause of occupational asthma in industrialized countries.
  
  
  OBJECTIVE
  We sought to investigate the utility of specific IgE measurement in the diagnosis of isocyanate-induced asthma.
  
  
  METHODS
  Fifty-eight of 101 patients referred for investigation were diagnosed as having isocyanate-induced occupational asthma by means of history, serial peak flow records, and bronchial provocation tests. Specific IgE antibodies to toluene diisocyanate:human serum albumin (HSA), diphenylmethane diisocyanate:HSA, and hexamethylene diisocyanate: HSA were measured in all patients by Phadebas RAST.
  
  
  RESULTS
  Twenty patients had a RAST ratio of 2 or greater to at least one isocyanate. Thirteen (28%) of the 46 patients with a positive provocation test response had a RAST ratio of 2 or greater, and nine (20%) had a RAST ratio of 3 or greater. Raising the RAST cut-off from 2 or greater to 3 or greater reduced its sensitivity but increased the specificity of the test to 100%. RAST measurement was most likely to be positive within 30 days of exposure. Serial measurements suggested that the half-life of the IgE antibodies was approximately 6 months. Evidence of cross-reactivity between isocyanate RAST responses was found in eight subjects.
  
  
  CONCLUSIONS
  Specific IgE to isocyanates is a more specific than sensitive index of occupational asthma. With a RAST score of 3 or greater, it is wholly specific and therefore diagnostic of isocyanate-induced asthma. The sensitivity of specific IgE measurement is highest when blood is taken less than 30 days from last exposure, which is consistent with the observed half-life.
authors.affiliation: Department of Occupational and Environmental Medicine, Imperial College School of Medicine (National Heart and Lung Institute), London, United Kingdom.
authors.forename: R D
authors.initials: RD
authors.lastname: Tee
authors.forename: P
authors.initials: P
authors.lastname: Cullinan
authors.forename: J
authors.initials: J
authors.lastname: Welch
authors.forename: P S
authors.initials: PS
authors.lastname: Burge
authors.forename: A J
authors.initials: AJ
authors.lastname: Newman-Taylor
mesh_terms: D000293:Adolescent; D000328:Adult; D000485:Allergens / Q000276:immunology*; D001249:Asthma / Q000175:diagnosis* / Q000276:immunology*; D001985:Bronchial Provocation Tests; D003429:Cross Reactions; D005260:Female; D006801:Humans; D007073:Immunoglobulin E / Q000097:blood / Q000276:immunology*; D017953:Isocyanates / Q000276:immunology*; D008297:Male; D008875:Middle Aged; D009784:Occupational Diseases / Q000175:diagnosis* / Q000276:immunology*; D012709:Serum Albumin / Q000276:immunology; D013997:Time Factors
chemical_list: D000485:Allergens; D017953:Isocyanates; D012709:Serum Albumin; D007073:Immunoglobulin E