Chest
Volume 100, Issue 2, August 1991, Pages 329-335
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Clinical Investigations
Outcome of Assessments for Occupational Asthma

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Among 154 referrals to a university hospital clinic for assessment of possible occupational asthma, the feasibility and results of different investigations were assessed using a consistent approach to all patients. A positive skin test to a workplace allergen (14 percent of all subjects), positive peak flow workplace changes (12 percent), improvement in methacholine response on holiday (9 percent), and/or positive specific challenge testing (14 percent) supported the diagnosis of occupational asthma in 61 subjects (39 percent of the total referrals). Fifty-one of these were related to a workplace sensitizer and ten to a presumed irritant. Occupational asthma was excluded in 48 subjects (31 percent) who had normal methacholine responsiveness within 24 hours of work (22 percent of the 154 subjects), peak flow readings no worse at work than on holidays (14 percent of the total referrals) and/or negative specific challenge testing (10 percent of the total referrals). Insufficient information could be obtained for a diagnosis in the remaining 45 subjects (28 percent). No single investigation was considered diagnostic in this study, as each could be positive or negative for other reasons.

(Chest 1991; 100:329-35)

Section snippets

MATERIALS AND METHODS

A retrospective review was performed on the files of 154 consecutive workers referred for assessment of possible occupational asthma. They were all seen in the clinics of the Gage Research Institute (35 workers) and the Toronto General Hospital (119 workers) between 1978 and 1987 by a single clinician, using the same diagnostic approach throughout.

All patients had symptoms thought by their referring doctor to be consistent with intermittent airflow limitation or bronchial hyperresponsiveness

Diagnostic Groups and Characteristics

Sixty-one of the 154 patients were finally diagnosed as having occupational asthma (Table 1), including 51 whose asthma was attributed to a workplace sensitizer and ten whose asthma was attributed to an irritant. In 45 other patients, a diagnosis of possible occupational asthma was reached, in 29 related to a sensitizer and in 16 related to an irritant exposure. In these patients, the findings were suggestive of occupational asthma, but objective tests were either inconclusive or could not be

DISCUSSION

This population showed a significant increase in atopic patients among those with a positive diagnosis of occupational asthma due to a specific sensitizer (Table 3) as has been reported in occupational asthma due to high-molecular-weight allergens.9, 10, 11 A minority of sensitizer-induced occupational asthma patients, 19 out of 51 (37 percent), had exposure and positive specific skin tests to a high-molecular-weight workplace allergen, but these accounted for most of the increase in atopy (84

ACKNOWLEDGMENTS

The authors wish to acknowledge the secretarial assistance of Peggy Murawnik, Beryl Gibson, and L. O'Connor in preparation of this manuscript.

REFERENCES (17)

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Manuscript received June 18; revision accepted Decensber 10.

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