Specific IgE to isocyanates: a useful diagnostic role in occupational asthma

J Allergy Clin Immunol. 1998 May;101(5):709-15. doi: 10.1016/S0091-6749(98)70181-2.


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.

Conclusion: 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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • Allergens / immunology*
  • Asthma / diagnosis*
  • Asthma / immunology*
  • Bronchial Provocation Tests
  • Cross Reactions
  • Female
  • Humans
  • Immunoglobulin E / blood
  • Immunoglobulin E / immunology*
  • Isocyanates / immunology*
  • Male
  • Middle Aged
  • Occupational Diseases / diagnosis*
  • Occupational Diseases / immunology*
  • Serum Albumin / immunology
  • Time Factors


  • Allergens
  • Isocyanates
  • Serum Albumin
  • Immunoglobulin E