The strength of recommendation grading (A–D, Good Practice Points) and level of evidence (I++ to 4 and *** to -) are defined at the end of the "Major Recommendations" field.
- Employers, health and safety personnel and health practitioners should be aware that at least 1 in 10 cases of new or recurrent asthma in adult life are attributable to occupation. ***Scottish Intercollegiate Guidelines Network (SIGN) A
*** SIGN 2++ Occupational factors are estimated to account for 9–15% of cases of asthma in adults of working age, including new onset or recurrent disease.
- Employers and their health and safety personnel should be aware of the very large number of agents known to cause occupational asthma and the risk of exposure to such agents. ** SIGN B
*** SIGN 2++ The most frequently reported agents include isocyanates, flour and grain dust, colophony and fluxes, latex, animals, aldehydes, and wood dust.
- Employers and their health and safety personnel should be aware that the major determinant of risk for the development of occupational asthma is the level of exposure to its causes. ** SIGN B
*** SIGN 2++ The risk of sensitisation and occupational asthma is increased by higher exposures to many workplace agents.
- Health practitioners should not use poorly discriminating factors, such as atopy, family or personal history of asthma, cigarette smoking, and human leukocyte antigen (HLA) phenotype, which increase individual susceptibility to exposure as a reason to exclude individuals from employment. * SIGN D
* SIGN 3 The positive predictive values of screening criteria are too poorly discriminating for screening out potentially susceptible individuals, particularly in the case of atopy where the trait is highly prevalent.
* SIGN 3 A previous history of asthma is not significantly associated with occupational asthma.
- Employers should implement programmes to prevent (i.e., reduce the incidence of) occupational asthma by removing or reducing exposure to its causes through elimination or substitution and, where this is not possible, by effective control of exposure. ** SIGN B
*** SIGN 2++ The risk of sensitisation and occupational asthma is increased by higher exposures to many workplace agents.
** SIGN 2+ Reducing airborne exposure reduces the incidence of sensitisation and occupational asthma.
* SIGN 3 The use of respiratory protective equipment reduces the incidence of, but does not completely prevent, occupational asthma.
- Employers and their health and safety personnel should ensure that when respiratory protective equipment is worn, the appropriate type is used and maintained, fit testing is performed and workers understand how to wear, remove, and replace their respiratory protective equipment. * SIGN D
* SIGN 3 The use of respiratory protective equipment reduces the incidence of, but does not completely prevent, occupational asthma.
- Employers and their health and safety personnel should inform workers about any causes of occupational asthma in the workplace and the need to report any relevant symptoms as soon as they develop. ** SIGN D
** SIGN 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.
** SIGN 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.
- Employers and their health and safety personnel should be aware that for many causes the risk of developing occupational asthma is greatest during the early years of exposure. ** SIGN C
** SIGN 2+ Sensitisation and occupational asthma are most likely to develop in the first years of exposure for workers exposed to enzymes, complex platinum salts, isocyanates, and laboratory animal allergens.
- Employers and their health and safety personnel should provide regular health surveillance to workers where a risk of occupational asthma is identified. Surveillance should include a respiratory questionnaire enquiring about work-related upper and lower respiratory symptoms, with additional functional and immunological tests, where appropriate. ** SIGN C
** SIGN 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.
** SIGN 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.
* SIGN 3 Health surveillance can detect occupational asthma at an earlier stage of disease, and outcome is improved in workers who are included in a health surveillance programme.
- Health practitioners should provide workers at risk of occupational asthma with health surveillance at least annually and more frequently in the first two years of exposure. ** SIGN C
** SIGN 2+ Sensitisation and occupational asthma are most likely to develop in the first years of exposure for workers exposed to enzymes, complex platinum salts, isocyanates, and laboratory animal allergens.
- Health practitioners should provide more frequent health surveillance to workers who develop rhinitis when working with agents known to cause occupational asthma and ensure that the workplace and working practices are investigated to identify potential causes and implement corrective actions. ** SIGN C
** SIGN 2+ Occupational rhinitis and occupational asthma frequently occur as comorbid conditions in the case of immunoglobulin E (IgE)-associated occupational asthma.
** SIGN 2+ Rhino-conjunctivitis is more likely to appear before the onset of IgE-associated occupational asthma.
* SIGN 2- The risk of developing occupational asthma is highest in the year after the onset of occupational rhinitis.
- Health practitioners should provide more frequent health surveillance to any workers who have preexisting asthma to detect any evidence of deterioration. Good Practice Point
- Health practitioners should consider the use of skin prick or serological tests as part of the health surveillance of workers exposed to agents that cause IgE-associated occupational asthma to assess the effectiveness of the control of exposure and the risk of occupational asthma among workers. Good Practice Point
** SIGN 2+ Skin prick testing and blood sampling of exposed workers to conduct immunological tests is feasible in the workplace.
- Health practitioners should enquire of any adult patient with new, recurrent, or deteriorating symptoms of rhinitis or asthma about their job, the materials with which they work, and whether their symptoms improve regularly when away from work. *** SIGN A
*** SIGN 2++ Occupational factors are estimated to account for 9–15% of cases of asthma in adults of working age, including new onset or recurrent disease.
*** SIGN 2++ The workers most commonly reported from surveillance schemes reported of occupational asthma include bakers and pastry makers, paint sprayers, nurses, chemical workers, animal handlers, food processing workers, timber workers, and welders.
** SIGN 2+ The workers reported from population studies to be at increased risk of developing asthma include bakers, food processors, forestry workers, chemical workers, plastics and rubber workers, metal workers, welders, textile workers, electrical and electronic production workers, storage workers, farm workers, waiters, cleaners, painters, plastic workers, dental workers, and laboratory technicians.
*** SIGN 2++ The most frequently reported agents include isocyanates, flour and grain dust, colophony and fluxes, latex, animals, aldehydes, and wood dust.
** SIGN 2+ In the clinical setting questionnaires that identify symptoms of wheeze and/or shortness of breath which improve on days away from work or on holiday have a high sensitivity, but relatively low specificity for occupational asthma.
- Employers and their health and safety personnel should assess exposure in the workplace and enquire of relevant symptoms among the workforce when any one employee develops confirmed occupational rhinitis or occupational asthma and identify opportunities to institute remedial measures to protect other workers. Good Practice Point
- Health practitioners should be aware that the prognosis of occupational asthma is improved by early identification and early avoidance of further exposure to its cause. ** SIGN B
** SIGN 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.
** SIGN 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.
- Health practitioners who suspect a worker of having occupational asthma should make an early referral to a physician with expertise in occupational asthma. Good Practice Point
- Health practitioners who suspect a worker of having occupational asthma should arrange for workers to perform serial peak flow measurements at least four times a day. ** SIGN D
** SIGN 3 Acceptable peak flow series can be obtained in around two-thirds of those in whom a diagnosis of occupational asthma is being considered.
* SIGN 3 The diagnostic performance of serial peak flow measurements falls when fewer than four readings a day are made.
** SIGN 3 There is high level of agreement between expert interpretations of serial peak flow records.
** SIGN 3 The sensitivity and specificity of serial peak flow measurements are high in the diagnosis of occupational asthma.
- Physicians should confirm a diagnosis of occupational asthma supported by objective criteria (functional, immunological, or both) and not on the basis of a compatible history alone because of the potential implications for future employment. ** SIGN B
** SIGN 2+ In the clinical setting questionnaires that identify symptoms of wheeze and/or shortness of breath which improve on days away from work or on holiday have a high sensitivity, but relatively low specificity for occupational asthma.
* SIGN 3 Free histories taken by experts have high sensitivity, but their specificity may be lower. These values may be affected by differences in language and populations.
** SIGN 2- Approximately one-third of workers with occupational asthma are unemployed up to 6 years after diagnosis.
** SIGN 2- Workers with occupational asthma suffer financially.
- Employers and their health and safety personnel should ensure that measures are taken to ensure that workers diagnosed as having occupational asthma avoid further exposure to its cause in the workplace. ** SIGN B
** SIGN 2+ The likelihood of improvement or resolution of symptoms or of preventing deterioration is greater in workers who are removed from exposure completely.
** SIGN 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 removal from exposure.
* SIGN 3 Redeployment to a low exposure area may lead to improvement or resolution of symptoms or prevent deterioration in some workers; however, there is contradictory evidence from other studies, which show that redeployment does not lead to improvement in symptoms or prevent deterioration of symptoms.
- Physicians treating patients with occupational asthma should follow published clinical guidelines for the pharmacological management of patients with asthma in conjunction with recommendations to avoid exposure to the causative agent. Good Practice Point
- Health practitioners should enquire about preexisting occupational asthma to agents that job applicants might be exposed to in their new job and advise affected applicants that they are not fit to undertake this work. ** SIGN B
** SIGN 2+ The likelihood of improvement or resolution of symptoms or of preventing deterioration is greater in workers who are removed from exposure completely.
** SIGN 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 removal from exposure.
* SIGN 3 Redeployment to a low exposure area may lead to improvement or resolution of symptoms or prevent deterioration in some workers; however, there is contradictory evidence from other studies, which show that redeployment does not lead to improvement in symptoms or prevent deterioration of symptoms.
Definitions
Royal College of General Practitioners Three Star System:
*** Strong evidence – provided by generally consistent findings in multiple, high quality scientific studies
** Moderate evidence – provided by generally consistent findings in fewer, smaller, or lower quality scientific studies
* Limited or contradictory evidence – provided by one scientific study or inconsistent findings in multiple scientific studies
- No scientific evidence – based on clinical studies, theoretical considerations, and/or clinical consensus
Revised Scottish Intercollegiate Guidelines Network Grading System
Levels of Evidence
1++ - High quality meta-analyses, systematic reviews of randomised controlled trials, or randomised controlled trials with a very low risk of bias
1+ - Well conducted meta-analyses, systematic reviews of randomised controlled trials, or randomised controlled trials with a low risk of bias
1- - Meta-analyses, systematic reviews of randomised controlled trials, or randomised controlled trials with a high risk of bias
2++ - High quality systematic reviews of case-control or cohort studies. High quality case-control or cohort studies with a very low risk of confounding, bias, or chance and a high probability that the relationship is causal
2+ - Well conducted case control or cohort studies with a low risk of confounding, bias, or chance and a moderate probability that the relationship is causal
2- - Case control or cohort studies with a high risk of confounding, bias, or chance and a significant risk that the relationship is not causal
3 - Non-analytic studies (e.g. case reports, case series)
4 – Expert opinion
Revised Scottish Intercollegiate Guidelines Network
Grades of Recommendation
A - At least one meta-analysis, systematic review, or randomised controlled trial rated as 1++, and directly applicable to the target population; or a systematic review of randomised controlled trials or a body of evidence consisting principally of studies rated as 1+, directly applicable to the target population, and demonstrating overall consistency of results
B - A body of evidence including studies rated as 2++, directly applicable to the target population, and demonstrating overall consistency of results; or extrapolated evidence from studies rated as 1++ or 1+
C - A body of evidence including studies rated as 2+, directly applicable to the target population and demonstrating overall consistency of results; or extrapolated evidence from studies rated as 2++
D - Evidence level 3 or 4; or extrapolated evidence from studies rated as 2+
Good Practice Points - The guidelines include good practice points where there is no, and nor is there likely to be, research evidence. They are based on the clinical experience of the research-working group, legal requirement, or other consensus.
