Management of a worker with occupational asthma

All the evidence linked statements are accompanied by a RCGP rating and a revised SIGN rating to indicate the level of evidence behind the statement. These are explained on the Evidence Review Methods page.

The outcome of interventions made after a confirmed diagnosis of occupational asthma may depend on a number of factors, including the age of the worker at the time of diagnosis and the agent to which employees are exposed. Studies in this area are open to considerable bias through subject selection.

What is the prognosis of occupational asthma?

Generally, occupational asthma is reported to have a poor prognosis and to be likely to persist and deteriorate unless identified early and managed effectively.

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2+

The symptoms and functional impairment of occupational asthma caused by various agents may persist for many years after avoidance of further exposure to the causative agent.

( Allard 1989, Barker 1998, ChanYeung 1982, ChanYeung 1987, Hudson 1985, Lemiere 1996, Lozewicz 1987, Mapp 1988, Marabini 1994, Merget 1994, Moller 1986, Munoz 2003, O'Donnell 1989, Padoan 2003, Paggiaro 1984, Paggiaro 1993, Pisati 1993, Rosenberg 1987, Tarlo 1995, Venables 1987, Venables 1989)

Which factors increase the probability of a favourable prognosis after a diagnosis of occupational asthma?

Complete avoidance of exposure may or may not improve symptoms and bronchial hyper-responsiveness. Both the duration of continued exposure following the onset of symptoms and the severity of asthma at diagnosis may be important determinants of outcome. Early diagnosis and early avoidance of further exposure, either by relocation of the worker or substitution of the hazard offer the best chance of complete recovery. Workers who remain in the same job and continue to be exposed to the same causative agent after diagnosis are unlikely to improve and symptoms may worsen.

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2++

The likelihood of improvement or resolution of symptoms or of preventing deterioration is greater in workers who have no further exposure to the causative agent.

( Burge 1982, ChanYeung 1982, Merget 1999, Moscato 1999, Pisati 1993, Rosenberg 1987, Tarlo 1997, Valentino 1994, Valentino 2002, Vandenplas 1995)

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2+

The likelihood of improvement or resolution of symptoms or of preventing deterioration is greater in workers who have relatively normal lung function at the time of diagnosis.

( ChanYeung 1982, ChanYeung 1987, Maghni 2004, Padoan 2003, Park 1997, Rosenberg 1987, Tarlo 1995)

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2+

The likelihood of improvement or resolution of symptoms or of preventing deterioration is greater in workers who have shorter duration of symptoms prior to diagnosis.

( ChanYeung 1982, Park 1997, Piirila 2000, Pisati 1993, Rosenberg 1987, Ross 1998, Tarlo 1995, Tarlo 1997)

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2+

The likelihood of improvement or resolution of symptoms or of preventing deterioration is greater in workers who have shorter duration of symptoms prior to avoidance of exposure.

( Hudson 1985, Park 1997, Piirila 2000, Rosenberg 1987, Ross 1998, Tarlo 1997)

What evidence is there for benefit of redeployment within the same workplace?

Ideally, complete and permanent avoidance of exposure is the mainstay of management. In practice, workers may reject this advice for social or financial reasons. If it is possible to relocate the worker to low or occasional exposure work areas, he or she should remain under increased medical surveillance. Where present, specific IgE can be monitored although this has not been shown to affect outcome.

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3

Redeployment to a low exposure area may lead to improvement or resolution of symptoms or prevent deterioration in some workers, but is not always effective.

( Burge 1982, Douglas 1995, Grammer 2000, Merget 1999, Pisati 1993, Rosenberg 1987)

What evidence is there for the benefit of the enhanced use of respiratory protective equipment?

Once sensitised, a worker's symptoms may be incited by exposure to extremely low concentrations of a respiratory sensitiser. Respiratory protective equipment is effective only insofar as it is worn when appropriate, that there is a good fit on the face and proper procedures are followed for removal, storage and maintenance. The few studies that investigate the effectiveness of respiratory protective equipment are limited to small studies in provocation chambers or limited case reports. There are no large studies of long-term outcome.

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3

Air fed helmet respirators may improve or prevent symptoms in some but not all workers who continue to be exposed to the causative agent.

( MullerWening 1998, Obase 2000, Pisati 1993, Slovak 1985, Taivainen 1998)

What is the impact of occupational asthma on employment?

There is consistent evidence derived from clinical and workforce case series in a limited number of countries that about one third of workers with occupational asthma are unemployed after diagnosis. The risk may (Axon 1995) or may not (Cannon 1995, Labarnois 2002) be higher than among other adult asthmatics although this has been examined in only three studies. The risk of unemployment may fall with increasing time after diagnosis (Ross 1998). There is consistent evidence that loss of employment following a diagnosis of occupational asthma is associated with loss of income. In comparison with other adult asthmatics those whose disease is related to work may find employment more difficult (Cannon 1995, Labarnois 2002).

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Approximately one third of workers with occupational asthma are unemployed up to 6 years after diagnosis.

( Ameille 1997, Axon 1995, Cannon 1995, Gannon 1993, Laoprasert 1998, Larbanois 2002, Marabini 1993, Ross 1998, Venables 1989)

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Workers with occupational asthma suffer financially.

( Ameille 1997, Axon 1995, Gannon 1993, Laoprasert 1998, Larbanois 2002)

What is the effectiveness of compensation being directed towards rehabilitation?

There are no studies that have made direct comparisons between different systems of rehabilitation either under different jurisdictions or within the same jurisdiction at different times.

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4

Systems that incorporate retraining may be more effective than those that do not.

( Ameille 1997, Malo 1993)

What is the effect of inhaled corticosteroids on recovery from occupational asthma?

A single small randomised-controlled trial has examined the effect of inhaled corticosteroids on the recovery from occupational asthma after cessation of exposure. Small but statistically significant improvements in some symptoms, peak flow and quality of life were reported.

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1+

Inhaled corticosteroids used after cessation of exposure may provide small clinical benefits to workers with occupational asthma.

( Malo 1996)