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J Allergy Clin Immunol. 1998 May;101(5):709-15.

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

Author information

1
Department of Occupational and Environmental Medicine, Imperial College School of Medicine (National Heart and Lung Institute), London, United Kingdom.

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.

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.

PMID:
9600510
DOI:
10.1016/S0091-6749(98)70181-2
[Indexed for MEDLINE]

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