Occupational Asthma Reference

Rachiotis G, Savani R, Brant A, MacNeill SJ, Newman Taylor AJ, Cullinan P., Outcome of occupational asthma after cessation of exposure: a systematic review, Thorax, 2007;62:147-152,

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Known Authors

Paul Cullinan, Royal Brompton Hospital, London, UK Paul Cullinan

Tony Newman Taylor, Royal Brompton Hospital, London Tony Newman Taylor

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Abstract

Background: Patients with occupational asthma, and their medical advisers, need valid information about the prognosis of their disease.

Methods: A systematic review of the published literature on the symptomatic and functional outcomes of occupational asthma was carried out after avoidance of exposure to the causative agent. Through a full search of electronic and bibliographic sources, original studies documenting complete recovery from asthma (n = 39,1681 patients) or improvement in non-specific bronchial hyper-responsiveness (NSBHR; n = 28,695 patients) were identified. The median duration of follow-up was 31 (range 6–240) months for studies of symptomatic recovery and 37 (6–240) months for studies of NSBHR. Most studies were of patients recruited from special clinics.

Results: Reported rates of symptomatic recovery varied from 0% to 100%, with a pooled estimate of 32% (95% CI 26% to 38%). These rates were lower with increasing age (p = 0.019) and among clinic based populations (p = 0.053). Patients with the shortest durations of exposure (76 months) had the highest rate of recovery (36%; 95% CI 25% to 50%), but the effect was not linear. The pooled prevalence of persistent NSBHR at follow-up was 73% (95% CI 66% to 79%). This figure was higher among patients whose disease was due to high-molecular-weight agents (p = 0.006) and, less clearly, those from clinic-based populations (p = 0.561). In between-study comparisons, no clear patterns of improvement relating to total duration of exposure or follow-up were found. From within-study comparisons there was some evidence that a shorter duration of symptoms was associated with a higher rate of symptomatic recovery.

Conclusion: The available data on the prognosis of occupational asthma are insufficiently consistent to allow confident advice to be given to patients with the disease. Clinicians and epidemiologists with an interest in this disease should consider a collaborative and carefully standardised study of the prognosis of occupational asthma.

Plain text: Background: Patients with occupational asthma, and their medical advisers, need valid information about the prognosis of their disease. Methods: A systematic review of the published literature on the symptomatic and functional outcomes of occupational asthma was carried out after avoidance of exposure to the causative agent. Through a full search of electronic and bibliographic sources, original studies documenting complete recovery from asthma (n = 39,1681 patients) or improvement in non-specific bronchial hyper-responsiveness (NSBHR; n = 28,695 patients) were identified. The median duration of follow-up was 31 (range 6-240) months for studies of symptomatic recovery and 37 (6-240) months for studies of NSBHR. Most studies were of patients recruited from special clinics. Results: Reported rates of symptomatic recovery varied from 0% to 100%, with a pooled estimate of 32% (95% CI 26% to 38%). These rates were lower with increasing age (p = 0.019) and among clinic based populations (p = 0.053). Patients with the shortest durations of exposure (76 months) had the highest rate of recovery (36%; 95% CI 25% to 50%), but the effect was not linear. The pooled prevalence of persistent NSBHR at follow-up was 73% (95% CI 66% to 79%). This figure was higher among patients whose disease was due to high-molecular-weight agents (p = 0.006) and, less clearly, those from clinic-based populations (p = 0.561). In between-study comparisons, no clear patterns of improvement relating to total duration of exposure or follow-up were found. From within-study comparisons there was some evidence that a shorter duration of symptoms was associated with a higher rate of symptomatic recovery. Conclusion: The available data on the prognosis of occupational asthma are insufficiently consistent to allow confident advice to be given to patients with the disease. Clinicians and epidemiologists with an interest in this disease should consider a collaborative and carefully standardised study of the prognosis of occupational asthma.

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Associated Questions

Registered users of this website have associated this reference with the following questions. This association is not a part of the BOHRF occupational asthma guidelines.

What is the prognosis of occupational asthma?
burgeps You can find an individual paper that supportsrecovery in anything from 0-100%, however there are a large number of workers who do not make a complete recovery (an estimate of 70% with great inhomogeneity)
Which factors increase the probability of a favourable prognosis after a diagnosis of occupational asthma?
burgeps Younger age and shorter exposure favoured complete resolution. Exposure to high molecular weight agents was associated with a greater propotion with increased non-specific reactivity at follow-up than those exposed to low molecular weight agents (many used to believe the converse).

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