What is the optimal management option for occupational asthma?

Table 1. Ancillary questions pertaining to the management of occupational asthma

What are the consequences of persistent exposure to the causal agent?

Is it possible to improve symptoms and lung function by pharmacological treatment in affected workers with persistent exposure?

What is the effectiveness of complete avoidance of exposure?

What is the effectiveness of reducing exposure through engineering control or relocation of affected workers?

What is the effectiveness of reducing exposure through personal protective equipment?

Table 2. Comparison between persistence and avoidance of causal exposure

Individual study data are presented as n/N. Pooled estimates are presented as n/N with or without % (95% CI). NA: not available; NSBHR: nonspecific bronchial hyperresponsiveness. ^#: “Global assessment of asthma”; ^¶: pooled estimates based on a random-effect model.

Table 3. Avoidance of exposure: characteristics and results of studies published between 2004 and 2010

First author [ref.]	Country	Agent	Study design	Duration of FU months	Symptom recovery n/N	Recovery of NSBHR n/N
Brant [34]	UK	Enzymes	Workforce-based survey of 35 out of 45 cases	37 (4–39)	5/35	NA
Klusackova [35]	Czech Republic	Various	Longitudinal FU of 37 cases (selection not stated) Clinic-based study	78 (12–216)	5/37	1/19
Labrecque [36]	Canada	Isocyanates	Retrospective cohort study of compensated subjects (89 randomly selected subjects)	∼24 for all subjects	4/79^¶	10/79
Park [38]	Korea	Reactive dyes	Longitudinal FU of 26 cases (selection not stated) Clinic-based study	Second visit: 104±22 (n=19)	NA	11/16
Park [37]	Korea	Reactive dyes	Longitudinal FU of 11 cases (selection not stated) Clinic-based study	164±28	0/11	3/11
Pisati [39]	Italy	Isocyanates	Longitudinal FU of 53 cases (selection of 25 patients rechallenged with TDI) Clinic-based study	58±7 (46–73)	10/25	12/25
Yacoub [40]	Canada	Various	Retrospective cohort study of 40 compensated subjects	44±34	6/40	10/40
Munoz [41]	Spain	Persulfate salts	Prospective longitudinal FU of 10 out of 11 cases Clinic-based study	63±19 (39–101)	2/7	5/7
Pooled estimates^#					32/234, 15.5%^¶ (8.3–27.1%)	52/197, 32.8% (16.8–54.3%)

Data for individual studies are presented as mean (range), mean±sd or mean±sd (range), unless otherwise stated. Pooled estimates are presented as n/N with % (95% CI). FU: follow-up; NSBHR: nonspecific bronchial hyperresponsiveness; NA: not available; TDI: toluene diisocyanate. ^#: pooled estimates based on a random-effect model; ^¶: the rate of symptom recovery was 19.2% (28 out of 155 subjects; 95% CI 11.2–30.9%) after exclusion of the study by Labrecque et al. [36], which used more stringent criteria of “clinical remission” defined by the absence of symptoms, NSBHR and medication.

Table 4. Assessment of respiratory protective equipment (RPE)

First author [ref.]	Design	Agent	Type of RPE	Effects of RPE
Muller-Wening [54]	Laboratory challenge Non-RCT study n=26 Exposure: 1 h, not quantified	Organic farm allergens	RPE with P2 filter: "Dustmaster" (n=21), "Airstream helmet" (n=4), "Airlite" (n=1)	Suppression of symptoms in 11 out of 26, reduction in 15 out of 26, but 4 required inhaled bronchodilator Reduction of the increase in airway resistance
Laoprasert [55]	Laboratory challenge RCT study with placebo n=9 Exposure: 1 h, quantified	Latex	Laminar flow HEPA–filtered helmet	Reduction of symptom score Reduction of the decline in FEV₁
Slovak [56]	Workplace exposure Non-controlled study n=8 Exposure: 6 weeks, not-quantified	Laboratory animals	Powered helmet respirator with AS-23-3 filter	Worsening of symptoms in 2 out of 8 (score not available) Peak flow variation at work in 2 out of 8
Kongerud [57]	Workplace exposure RCT study n=19 workers with nonsevere disease Exposure: 2 weeks, not quantified	Aluminium pot room	AH60 Airsteam helmet	Reduction of symptom score in 10 out of 17 subjects (nonsignificant) Improvement in the mean peak flow values
Taivainen [58]	Workplace exposure Non-RCT study n=24 Exposure: 10 months, not quantified	Farming	Powered dust respirator helmet with P2 filter	No effect on respiratory symptoms with the exception of sputum, rhinitis symptoms, corticosteroid treatment, and number of sick leaves Increase in morning peak flow and reduced daily peak flow variability

RCT: randomised controlled trial; HEPA: high-efficiency particulate arrest; FEV₁: forced expiratory volume in 1 s.

Table 5. Recommendations

Recommendation	Strength of recommendation	Quality of evidence
Patients, physicians, and employers should be informed that persistence of exposure to the causal agent is likely to result in a deterioration of asthma symptoms and airway obstruction	Strong	Moderate
Patients and their attending physicians should be aware that complete avoidance of exposure is associated with the highest probability of improvement, but may not lead to a complete recovery from asthma	Strong	Moderate
Reducing exposure to the causal agent can be considered an alternative to complete avoidance in order to minimise the adverse socioeconomic consequences, but available evidence is insufficient to recommend this option as a first-choice therapeutic strategy. This approach requires careful medical monitoring in order to ensure an early identification of asthma worsening	Weak	Low
The use of respiratory protective devices should not be regarded as a safe approach, especially in the long term and in patients with severe asthma	Strong	Low
Anti-asthma medications should not be regarded as a reasonable alternative to environmental interventions	Strong	Very low
The pharmacological treatment of work-related asthma should follow the general recommendations for asthma	Strong	Moderate

The strength of the recommendations and the quality of underlying evidence were graded using the Grading of Recommendations Assessment, Development and Evaluation approach [67].