1 British Thoracic Society Clinical Statement on Occupational Asthma 2 3 4 5 Draft 14 July 2021 6 7 8 Available for public consultation from 9 Thursday 5 August to Friday 17 September 2021 10 11 12 13 14 Contact: 15 British Thoracic Society, 16 17 Doughty St, London WC1N 2PL 17 18 [email protected] 19 20 21 A response form is available on the BTS website. 22 Please send your responses to Miguel Souto by 5pm on Friday 17th 23 September 2021 24 25 26 27 28 1 29 Authors: 30 Dr Christopher Barber*, Professor Paul Cullinan, Dr Johanna Feary, Professor David Fishwick, Dr 31 Jennifer Hoyle, Dr Hayley Mainman, Dr Gareth Walters (Author order to be confirmed by the group) 32 * Chair 33 Contents: 34 Section 1: Introduction 35 Section 2: Work context 36 Section 3: Diagnosis 37 Section 4: Management 38 Section 5: Prognosis 39 Section 6: Audit 40 Appendix 1: Irritant induced asthma 41 List of tables and figures 42 Table 1. Frequently reported causes of occupational asthma, by molecular weight. 43 Table 2. Legislation and guidance relevant to workplace respiratory diseases. 44 Table 3. Key elements of the occupational history for patients with suspected OA. 45 Table 4. Diagnostic tests for OA; a summary. 46 Table 5: Summary of factors influencing management of OA. 47 Table 6: Summary of potential employment options following a diagnosis of OA. 48 Table 7. Prognostic indicators in OA. 49 50 Figure 1. Classification of work-related asthma. 51 Figure 2. Diagram representing the “hierarchy of control measures” from most effective at the top, 52 to least effective at the bottom. 53 Figure 3: Recommended algorithm for the assessment and referral of patients with possible 54 occupational asthma presenting in primary or non-specialist secondary care. 55 Figure 4. Diagram summarising the key elements of OA Management. 56 57 Word count: Approx. 10246 (excluding references and Appendix) 58 References: 94 59 60 61 62 63 64 65 66 67 68 2 69 This British Thoracic Society (BTS) Clinical Statement addresses occupational asthma and includes key 70 clinical practice points. In an era in which medical practice is increasingly determined by evidence- 71 based guidelines, it must be acknowledged from the outset that there is little or no published evidence 72 for some of the areas covered in this Statement; thus, some of the recommendations are based on 73 expert opinion and accumulated clinical experience. 74 Methodology 75 The Clinical Statement Group (CSG) was chaired by Dr Chris Barber. Membership was drawn from 76 current and former members of the BTS Occupational and Environmental Lung Disease Specialist 77 Advisory Group. The CSG identified key areas requiring Clinical Practice Points. The overall content 78 was developed to reflect the scope approved by the BTS Standards of Care Committee (SOCC). 79 Following discussions of broad statement content, individual sections were drafted by group 80 members. A final edited draft was reviewed by the BTS SOCC before posting for public consultation 81 and peer review on the BTS website in (date to be confirmed). The revised document was re-approved 82 by the BTS SOCC in TBC before final publication. A sentence will be added to cover lay input sought at 83 consultation stage. 84 85 SUMMARY OF CLINICAL PRACTICE POINTS 86 SECTION 1 - INTRODUCTION 1. Healthcare professionals should be aware that occupational exposures account for around 1 in 6 cases of asthma in adults of working age. 2. Over 400 causes of OA have been described; these are categorised as high or low molecular weight ‘respiratory sensitisers’. 3. Although individual susceptibility plays a key role, the main risk factor for the development of OA is the level of allergen exposure in the workplace. SECTION 1 – WORK CONTEXT 1. Health surveillance is a form of workplace screening that can identify OA cases early. In the UK, it usually consists of an annual symptom questionnaire and spirometry. 2. Workers who “fail” health surveillance due to reported symptoms or abnormal lung function should be referred as soon as possible to a specialist with expertise in OA. SECTION 3 – DIAGNOSIS 1. Many patients with OA in the UK are diagnosed at a late stage; healthcare professionals should be aware of the important benefits of recognising cases early. 2. All patients of working age with new symptoms suggestive of asthma, reappearance of childhood asthma, deteriorating asthma control, or unexplained airway obstruction, should be asked about their job, and whether their symptoms are the same, better or worse on days away from work. 3. Symptomatic asthma patients in high-risk jobs, and those reporting work-related asthma symptoms, should be referred as quickly as possible for specialist assessment (where possible, directly to a specialist occupational lung disease service) 3 4. A diagnosis of OA has important health and employment implications and should not be made based on a compatible history alone. 5. The diagnosis of OA is most easily made prior to workplace adaptations and starting maintenance treatment. 6. Objective tests commonly used in the UK include skin prick tests, specific IgE antibody levels, and serial measures of PEF or airway responsiveness; workplace and specific inhalation challenges are less commonly required for OA diagnosis. SECTION 4 - MANAGEMENT 1. Managing patients with OA can be complex and should wherever possible be carried out by a physician with specialist expertise in this condition. 2. It is important to educate patients with OA that the best opportunity for improved asthma control comes from early, and complete, cessation of exposure to the cause. 3. Management of OA includes standard pharmacotherapy, asthma education and smoking cessation advice, following national guidelines. 4. Patients with OA may have co-existing and related conditions (e.g. occupational rhinitis and breathing pattern disorder, ILO, anxiety and depression) that require assessment and treatment. 5. Clinicians should work in partnership with patients to develop (and adapt as necessary) a personalised management plan aiming for the best possible balance between long-term health and employment. 6. Where consent is given, liaising directly with occupational health providers and/or employers gives the best chance of suitable workplace adaptations being made, to keep patients and their co-workers safely employed. 7. Patients with OA should be provided with written information confirming their diagnosis, the implications this has on their current and future jobs, as well as IIDB and civil compensation advice. 8. Whilst there is potential for on-going exposure to the cause, patients with OA should remain under specialist follow up to monitor asthma control, lung function and the impact of any workplace interventions. SECTION 5 - PROGNOSIS 1. Around 1 in 6 patients with OA meet established criteria for severe asthma. 2. Prognosis in OA is largely determined by asthma severity at the time of diagnosis, and whether workers continue to be exposed to the cause thereafter. 3. Around 25-30% of OA patients who permanently cease exposure will make a full recovery, and another 30-35% will report a reduction in symptoms with treatment. 4. Patients with OA who remain exposed to the cause are at risk of accelerated lung function decline, resulting in fixed airflow obstruction. 5. Patient with OA have an increased risk of unemployment, with approximately 1 in 3 being out of work 3-5 years after diagnosis. 6. Anxiety and depression are common in OA, affecting up to half of patients. 87 88 89 4 90 Section 1: Introduction 91 Asthma is a common health condition in the UK adult population, affecting over 5 million individuals. 92 For those in employment, asthma control may be adversely affected by factors in the workplace, and 93 the term “work-related asthma” (WRA) is used.1 Although the true frequency of this condition is 94 unknown, it is relatively common, affecting around 20-25% of working individuals with asthma.2-4 95 WRA is subdivided into three main phenotypes – work-aggravated asthma, allergic occupational 96 asthma due to sensitisation, and irritant-induced asthma1 (Figure 1). 97 98 99 100 101 Figure 1. Classification of work-related asthma. 102 103 Work-related asthma Occupational asthma Work-aggravated asthma Allergic OA Irritant-induced (sensitisation) asthma 5 104 Patients with work-aggravated asthma (WAA) either have pre-existing asthma, or develop 105 coincidental adult-onset asthma, and report symptoms that are made worse by non-specific factors 106 in the workplace. Common causes of WAA include extremes of workplace temperature or humidity, 107 exertion from manual work tasks, workplace stress or anxiety, and exposure to non-specific dusts, 108 fumes, or air pollution. 109 In contrast, occupational asthma is caused by airborne exposures in the working environment, and 110 accounts for around 1 in 6 cases of adult asthma5. This condition is further sub-divided into two 111 separate conditions; irritant-induced asthma (IIA, covered in Appendix 1) and occupational asthma 112 due to allergic sensitisation (the main topic of this document; from now on referred to simply as “OA”). 113 Although there are over 400 known causes of OA (known as asthmagens), most cases in the UK are 114 caused by a small number of workplace allergens, most commonly flour dust or isocyanates6. 115 Asthmagens are usually divided into high (HMW) or low molecular weight (LMW) sensitisers7; 116 commonly reported causes are shown in Table 1. OA caused by repeated exposure to HMW proteins 117 is an IgE-associated response, involving T-helper cells. This immune mechanism is also known to be 118 relevant to a small number of LMW causes (e.g., acid anhydrides and platinum salts), but for the 119 majority the immune pathways responsible for sensitisation remain to be determined8.