Need for monitoring nonspecific bronchial hyperresponsiveness before and after isocyanate inhalation challenge.
BACKGROUND
Specific and nonspecific bronchial responsiveness may decline or disappear after cessation of exposure in the workplace in patients with occupational asthma, leading to false-negative specific inhalation challenge (SIC) results.


METHODS
Twenty-two patients with suspected diisocyanate-induced asthma were studied. SIC with diisocyanates (toluene diisocyanate [TDI] or hexamethylene diisocyanate [HDI]) was carried out in a 7-m(3) dynamic chamber up to a maximum concentration of 19 parts per billion for 120 min. Methacholine inhalation challenges were performed before and 24 h after SIC with TDI or HDI. Patients who did not show an asthmatic reaction after SIC but had a greater than twofold reduction in provocative concentration of methacholine causing a 20% fall in FEV(1) (PC(20)) after the first isocyanate challenge underwent a second isocyanate SIC 2 days later.


RESULTS
The first SIC with isocyanates elicited an asthmatic reaction in 13 patients (59%). In five patients who did not show an asthmatic reaction after the first SIC, PC(20) exhibited more than a twofold reduction. In three of the five patients, a second SIC with isocyanates elicited an immediate positive asthmatic reaction. Therefore, 3 of 16 patients (19%) were ultimately shown to have bronchial responsiveness to isocyanate; occupational asthma was demonstrated due to post-SIC monitoring of bronchial hyperresponsiveness to methacholine.


CONCLUSIONS
PC(20) should be systematically assessed before and after SIC with isocyanates in the absence of significant changes in FEV(1) during SIC to avoid false-negative results.
Sastre
Joaquín
J
Fundación Jiménez Díaz, Allergy Department, Madrid, Spain. jsastre@fjd.es
Fernández-Nieto
Mar
M
Novalbos
Ana
A
De Las Heras
Manuel
M
Cuesta
Javier
J
Quirce
Santiago
S
D000328:Adult; D001249:Asthma / Q000503:physiopathology*; D016535:Bronchial Hyperreactivity; D001985:Bronchial Provocation Tests; D003485:Cyanates; D005188:False Negative Reactions; D005260:Female; D005541:Forced Expiratory Volume; D006801:Humans; D017953:Isocyanates; D008297:Male; D008875:Middle Aged; D008991:Monitoring, Physiologic; D009784:Occupational Diseases / Q000503:physiopathology*; D011446:Prospective Studies; D014051:Toluene 2,4-Diisocyanate
D003485:Cyanates; D017953:Isocyanates; C015262:1,6-hexamethylene diisocyanate; D014051:Toluene 2,4-Diisocyanate