Chest
Volume 103, Issue 4, April 1993, Pages 1123-1128
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Clinical Investigations
Bronchial Hyperresponsiveness and Toluene Diisocyanate: Long-term Change in Sensitized Asthmatic Subjects

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Long-term change in nonspecific and specific bronchial hyperresponsiveness was studied in 16 subjects with asthma induced by toluene diisocyanate (TDI). A significant positive correlation between months of follow-up and provocative dose inducing a 20 percent fall in FEV1 (PD20FEV1) methacholine was observed in 5 of 16 subjects. In 4 of these 5 subjects, a PD20FEV1 >1 mg of methacholine was observed 30 to 48 months after the end of TDI exposure. In most subjects, nonspecific bronchial hyperresponsiveness did not change. Nine of 16 subjects became nonresponsive to TDI at follow-up examination, but only 3 of these showed a significant increase in PD20FEV1 methacholine. Seven subjects were still responsive to TDI. Recovery from TDI-induced asthma can occur and only after long-term work cessation. Nonspecific bronchial hyperresponsiveness to methacholine can persist even in the absence of bronchial hyperresponsiveness to TDI, suggesting permanent chronic damage to mechanisms controlling airway tone.

Section snippets

Subjects

We studied 16 subjects with TDI-induced asthma over a followup period of 48 months (range, 18 to 73 months), during which nonspecific bronchial responsiveness to methacholine was measured at least 3 times (mean, 6.5 ± 2.5).

The diagnosis of TDI-induced asthma was assessed when the subjects were still at work, on the basis of the following findings: (a) symptoms of bronchoconstriction related to the occupational exposure (spray painting in the furniture industry); (b) presence of NSBH to

RESULTS

At diagnosis, baseline FEV1 of the 16 patients was 81.7 ± 12.4 percent (Table 1). The duration of exposure to TDI in the furniture industry was 20.7 ± 8.9 years, and the duration of symptoms before diagnosis was 3.8 ± 4.1 years (range, 0.5 to 15 years). However, 11 of 16 subjects referred had symptoms for 3 or fewer years. Eight out of 16 subjects were nonsmokers, 6 were ex-smokers, and 2 were current smokers.

Immediately after diagnosis, nine subjects completely stopped working. The remaining

DISCUSSION

Our study shows that cessation of occupational exposure to TDI leads to recovery of specific and nonspecific bronchial hyperresponsiveness only in a small percentage of cases, and that such a recovery requires a long time to develop. Our data also show that NSBH to methacholine can persist even after specific responsiveness to TDI discontinues. After work cessation, NSBH persisted in most patients despite a mild improvement in asthmatic symptoms and a reduced need for drug therapy.

The analysis

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    Supported in part by grants 87.00182.04 and 88.00593.04 from the Italian National Research Council and by a grant from the Italian Ministry of Education.

    Manuscript received January 13; revision accepted August 10.

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